15 Vertigo and imbalance

The mechanism for maintaining balance in man is complex. Vision, proprioception, and vestibular inputs are integrated in the central nervous system, and modulated by activity from the cerebellum, the extrapyramidal system, the reticular formation, and the cortex (Fig. 15.1). This integrated, modulated information provides one mechanism for control of oculomotor activity, controls posture, gait, and motor skills and allows perception of the head and body in space. Recent evidence also supports an effect upon autonomic function, cognition, and emotion. The complexity of the system is such that pathology in a variety of different bodily systems, including the endocrine system, the cardiovascular system, and the haemopoietic system, can impact upon vestibular activity, in addition to primary otological and neurological pathology.

Patients with dysfunction in the vestibular end-organs or vestibular pathways commonly complain of symptoms of dizziness, vertigo, unsteadiness, light-headedness, imbalance, and a plethora of synonyms associated with a sense of instability. Not infrequently, in an attempt to define their ‘unphysiological’ experience, patients use rather vague and imprecise semantics. The clinical distinction between dizziness, a symptom of non-specific pathological significance, and vertigo, a hallucination or illusion of movement, is rarely made, although the latter is a cardinal manifestation of a disorder of the vestibular system (Dix 1973). Ten to 20 per cent of all ‘dizzy’ patients are reportedly seen in neurology clinics (Dieterish 2004), therefore it behoves the neurologist to have a clear diagnostic strategy, including knowledge of detailed neuro-otological examination, to enable appropriate diagnosis and management of the patient with vestibular symptoms.

The common symptoms of vertigo, dizziness, and disequilibrium represent 5 to 10 percent of all patients seen in general practice and 10 to 20 per cent of all patients seen by neurologists and otolaryngologists (Dieterish 2004). Yardley and co-workers (1998) in a community study of a random sample registered in four north London general practices, identified that more than one in five of the population had experienced dizziness in the past month, and 30 per cent had suffered symptoms of dizziness for more than 5 years. The German Health Questionnaire Study (Neuhauser et al. 2005) reported vestibular vertigo as common in the general population affecting more than 5 per cent of adults in a year, and estimated a life-time prevalence of vestibular vertigo at 7.8 per cent. They concluded that the frequency and healthcare impact of vestibular symptoms at the population level have been underestimated. One-third of the population has suffered symptoms of balance disorder by the age of 65 years (Roydhouse 1974), while by the age of 88 to 90 years, 45 to 50 per cent of the population suffer symptoms of balance dysfunction (Jonsson et al. 2004). In children, balance symptoms are generally considered to be less frequent, but a recent study has reported that 8 per cent of 1- to 15-year-olds in the general population have suffered dizziness and vertigo, and of these, 27 per cent reported symptoms which were sufficiently severe to interrupt activity (Niemensivu et al. 2006).

Balance disorders in children are frequently ignored, as they are dismissed as problems of behaviour or lack of coordination (Tusa et al. 1994). However the failure to diagnose vestibular pathology and the paucity of vestibular information related to children may be explained by:

Notwithstanding this, undiagnosed vestibular disorders in children are associated with psychological dysfunction, loss of time from school, and considerable family anxiety.

In adults, peripheral vestibular disorder of sufficient severity for the patient to present to a tertiary neuro-otological service led to 85 per cent of the population taking an average of nine months off work, despite the mean age of the patients being only 38 years (Eagger et al. 1992). The same study reported that two-thirds of patients in this group had suffered psychiatric symptoms of depression, anxiety, panic attacks, and avoidance behaviour in a three-to four-year review period.

Moreover, vestibular symptoms are the commonest cause of failure to return to work after head or whiplash injury (Luxon 1996), and Neuhauser and colleagues (2004) reported that 80 per cent of individuals with vertigo suffered interruption of daily activities or sick leave, and required a medical consultation. Thus both the occupational and healthcare economic impact of this symptom complex are significant.

In terms of healthcare expense, the low level of training in vestibular medicine leads to multiple medical attendances prior to diagnosis. Of patients seen in a London teaching hospital neuro-otology clinic, 63 per cent had had two or more previous specialist consultations prior to a neuro-otological diagnosis. The National Institutes of Health have reported that a patient with peripheral vestibular pathology visits a mean of 4.5 physicians prior to receiving a correct diagnosis. The poor diagnostic pathways for vertigo lead to unwarranted use of expensive investigations such as MRI (Halmagyi et al. in press; MacDonald and Melhem 1997).

The cost to the Health Service of disorders of balance in the elderly is still greater. In a typical primary care trust catchment of 150,000 population, 30,000 will be over the age of 65, and one-third of this group will fall each year, with half of them falling repeatedly, i.e. 5,000 high-risk fallers (American Geriatric Society, British Geriatric Society and American Academy of Orthopaedic Surgeons 2001). Eighty per cent of older people presenting to an emergency department with an unexplained fall had symptoms of vestibular impairment (Pothula et al. 2004); it is well recognized that falls are the commonest cause of accidental death in over 75-year-olds (Downton 1993). Thus in the elderly, the social and economic impact of vestibular dysfunction is high.

An interesting study by one US airline between 1995 and 2000 illustrated that neurological symptoms comprised the single largest category of in-flight incidents requiring medical consultation (Sirven et al. 2002). Of these 2042 incidents, just over 15 per cent resulted in unscheduled emergency landings or diversions with ‘dizziness and vertigo’ being the commonest precipitants in the neurological category, with an estimated total cost of approximately three million US dollars.

The internal ear comprises the membranous labyrinth, which lies within the bony labyrinth, buried within the petrous temporal bone. The inner ear includes both the cochlea—the auditory end-organ (Section 14.2)—and five vestibular receptors, one in each of the three semi-circular canals, and two otolith organs, the utricle and saccule, within the vestibule (Fig. 15.2). The vestibular sensory epithelium is comprised of type 1 and type 2 hair cells, together with supporting cells, which are covered with a gelatinous membrane, the cupula, in the semi-circular canals, and the otolithic membrane, which in addition contains calcium carbonate crystals termed otoconia, in the saccule and utricle (Fig. 15.3).

The vestibular receptors, or cristae, of the semi-circular canals respond to angular acceleration in the three planes of space, but are insensitive to gravity or head position. The otolith organs, the saccule and utricle, lie approximately vertically and horizontally within the vestibule, and respond to linear head accelerations. A force parallel to the surface of the sensory epithelium of each of the vestibular receptors provides the maximal stimulus.

Physiologically, the vestibular system on either side of the head works in parallel in a push–pull mechanism Thus, when the head is turned to the right, the right horizontal semi-circular canal increases its firing rate, whereas the left decreases. This excitation/inhibition in vestibular neural activity is transmitted to the vestibular nuclei, modulated specifically by the cerebellum which controls the amplitude and timing of movements, and passes to the thalamus, and from thence to the parieto-insular vestibular cortex.

A data bank of vestibular, visual, and proprioceptive signals, associated with every movement, is established in the reticular formation of the brain stem (Wuyts and Boudewyns in press). The sensory inputs generated by movements are compared against this database. Under normal circumstances there is no discrepancy, and reflex oculomotor and motor responses result in appropriate eye and body movement at a subconscious level (Fig. 15.4). Mismatch of data because of an abnormal sensory input may lead to the generation of a perception of imbalance, an abnormal vestibulo-ocular reflex response manifesting as nystagmus, or abnormal vestibulo-spinal activity with falling to one side or veering when walking.

In addition, there is extensive convergence of vestibular and autonomic afferent information in the brain stem and cerebellum, which allows for coordination of the motor response with autonomic responses during movement or changes in posture (Pagarkar and Luxon in press). Moreover, connections at various levels of the central vestibular system with the locus coeruleus, the limbic system and other brain regions which control affective responses, mood, and arousal may underlie the observed overlap between psychiatric and vestibular disorders (Balaban 2002; Furman et al. 2005).

Balance is maintained as a consequence of the postural body schema, which is an internal representation of body posture, including body geometry, movements, and orientation with respect to gravity. The body is orientated with respect to the upright posture by the gravity receptors in the labyrinth, vision, and possibly body gravity receptors. Postural tone depends not only on tonic labyrinthine input, which regulates the tonic activity of the postural extensor muscles, controlling the joints of the limbs, and orientating the head in space, but is also modulated through the myotatic reflex loop, neck reflexes, lumbar reflexes, and positive supporting reactions. Vision and vestibular inputs enable orientation of the head in space, while somatosensory receptors provide information with respect to head and body orientation. The multiple sensory inputs used for balance are integrated within the central nervous system to interpret the body’s orientation and allow preservation of balance with dynamic equilibrium. As with the efferent copy of sensory inputs highlighted above, the information for balance is compared to the internal model of the body such that motor commands are generated to maintain and regain body equilibrium. To remain upright in the presence of gravity, the central nervous system regulates the relationship between the centre of mass of the body and the base of support, the feet (Horstmann and Dietz 1990). Stability demands that two conditions are met:

A fall will result when there is a disturbance of postural equilibrium, for example a perturbation that precipitates the loss of balance and failure of the balance control system to compensate adequately for that perturbation (Maki and McIlroy 2003).

Postural control is not organized as a single unit, but inde-pendent control of the position and orientation of the head, the trunk and forearm segments have been shown to exist. Movements which destabilize posture have been shown to be preceded by activation of postural muscles known as anticipatory postural adjustments. So in addition to feedback processes, the postural system is also supported by anticipatory actions which bring about displacements of the centre of body mass to meet environmental conditions (Massion and Woollacott 1996). Balance control can be improved by training and learning, and varies widely between normal healthy subjects.

Physiological. Dizziness is a normal response to stimulation of the vestibular apparatus or as a consequence of unfamiliar visual, somatosensory, and vestibular interactions that underpin normal balance. For example a child on a roundabout or a swing may feel disorientated, an elderly person altering their visual input with new glasses may feel disorientated and a passenger in a train watching the train next to them move, may feel that they are moving rather than the adjacent train.

Moreover, motion sickness, a sensation of nausea together with vomiting precipitated by unfamiliar and unusual motion with atypical sensory inputs, for example, reading during a car journey or riding on an elephant, or travelling in a boat are all well recognized physiological syndromes of vestibular stimulation, with ‘mismatch’ of the sensory signals for balance (Brandt 1999a). Space sickness, in which the normal gravitational force on the otoliths is absent results in a ‘mismatch’ of semicircular canal and otolith inputs giving rise to a similar motion sickness phenomenon (Lackner and Graybiel 1986).

Pathological mechanisms giving rise to the symptom complexes characteristic of vestibular dysfunction can be broadly divided into ‘vestibular’, ‘medical’, and ‘neurological’ causations.

Following an acute unilateral vestibular deafferentation, as may occur with many pathologies, the patient presents with acute vertigo, nausea, vomiting, and ataxia, but is gradually rendered asymptomatic over a period of approximately 6 weeks to 6 months, by mechanisms collectively known as cerebral compensation. The structures underpinning compensation include the brain stem, cerebellum, and cortical structures (Gonshor and Melvill Jones 1976; Ito 1984; Smith and Curthoys 1989; Curthoys and Halmagyi 1995). In addition, for optimal recovery, all the sensory inputs, including vision, somatosensory afferents, and remaining labyrinthine function, are required (Lacour and Xerri 1981; Luxon 1997; Halmagyi et al. 2003a). Furthermore, integrity of both the

vestibular nerve (Cass and Goshgarian 1991) and of the central vestibular connections is necessary (Petrone et al. 1991).

Physiologically, compensation depends upon physical activity (Lacour et al. 1976; Igarashi et al. 1981) and vision (Courjon et al. 1977). The effect of abolition of movement using a plaster cast immediately after vestibular neurectomy in baboons delays the recovery of balance (Fig. 15.6). In addition, it has been demonstrated that the occipital lobe is necessary for compensation (Fetter et al. 1988), and loss of proprioception by transection of the cervical spinal cord also delays vestibular recovery (Schaeffer and Meyer 1973).

The majority of cases of unilateral peripheral vestibular dysfunction recover effectively and spontaneously by cerebral compensation (Fig. 15.7). However, a percentage of patients fail to improve spontaneously, and require vestibular rehabilitation with physiotherapy. This intervention relies upon promoting visual, proprioceptive, and vestibular stimulation by means of systemic or customized exercises. A number of factors have been identified, which predispose to failure of compensation (Fig. 15.8) or decompensation from a previously recovered state. In animals, there is some evidence of a critical period following vestibular loss, during which, if appropriate stimuli are not received, recovery is delayed, and the adaptive and substitution mechanisms of compensation do not become established (Lacour 1984). Conversely, Pavlou et al. 2004 evaluating clinical populations have shown that neither duration of symptoms nor age have been identified as negative prognostic factors in outcome for vestibular rehabilitation programmes (Shepard et al. 1993). However, financial compensation, head injury, and severe postural control abnormalities were reported to be poor prognostic indicators.

Failure of compensation may follow a single acute episode of unilateral labyrinthine loss, and results in the patient presenting as a vestibular invalid with constant disorientation and instability (Fig. 15.9A). Alternatively, there may be some compensation with marked setbacks and fluctuations and little overall recovery (Fig. 15.9B). An alternative pattern of events is the patient who recovers normally but then suffers repeated episodes of decompensation (Fig. 15.9C). All three patterns are commonly associated with patients who develop psychological symptoms in association with peripheral vestibular pathology (Jacob et al. 2003; Eagger et al. 1992).

If both labyrinths are destroyed sequentially, and compensation has occurred for the first unilateral loss, a second acute peripheral vestibular syndrome ensues. However, if both labyrinths are lost in rapid succession, or prior to compensation for the first loss, there is no acute vertiginous syndrome, as there is no left–right asymmetry in vestibular nucleus activity. However the long-term effects of

bilateral vestibular failure are the same, irrespective of whether the two labyrinths became impaired simultaneously or sequentially. The patient will experience chronic vestibular dysfunction known as Dandy’s syndrome (Syms and House 1997). This syndrome is characterized by three key factors, resulting from reduced afferent input to the vestibulo-ocular, vestibulospinal, and vestibulocortical pathways:

Nevertheless, patients with bilateral vestibular hypofunction or failure can compensate remarkably well, and benefit from intensive vestibular rehabilitation programmes (Brown et al. 2001)

Medical causes may be associated with vascular pathologies giving rise to presyncope, the drop in blood pressure. This in turn may result in ischaemia of vestibular nuclei or the labyrinth with a sense of light-headedness or vertigo. This situation may appertain in cases of orthostatic hypotension, simple vasovagal attacks, cardiac conditions with low cardiac output, and dysrrhythmias.

Certain haematological disorders such as anaemia and hyperviscosity syndromes may alter blood flow and reduce oxygen supply to the vestibular nuclei presenting with light-headedness, faintness, or vertigo.

Hypoglycaemia is most commonly associated with hypoglycaemic drug treatment in diabetics, but may occur with insulinomas or in association with fasting or post-prandial functional hypoglycaemia.

Drug induced dizziness may result from a variety of mechanisms and many drugs list ‘dizziness’ as a side effect. However, specific care should be taken with drugs used in the treatment of cardiovascular disease, for example, beta blockers, anti-anginal agents, hypotensive agents, anti-dysrhythmics, all of which may alter blood flow and produce presyncope. Drugs used in the treatment of diabetes, hormonal preparations, both steroids and non-steroidal anti-inflammatory agents, psychotropic drugs including anticonvulsants, sedatives, tranquillizers and antidepressants, and certain analgesics also are commonly associated with disequilibrium. Recreational drugs including alcohol, narcotics and ‘soft’ drugs may all present with disordered balance. The ototoxic effect of certain chemotherapeutic and aminoglycoside antibiotics, particularly gentamicin are well documented.

Neurological causes of imbalance may be associated with primary neurological disease affecting the vestibular pathways infra-tentorially within the brainstem and cerebellum, or supra-tentorially and the majority of neurological disorders may be accompanied by dizziness or vertigo, or imbalance. Many psychological disorders may also include symptoms of disorientation and dissociation or depersonalization including acute anxiety, panic attacks, depression, phobias, and avoidance behaviour. It should be emphasized that these psychological conditions may also present following the onset of a vestibular disorder (Jacob et al. 2003).

Many of these conditions are noted in this chapter, as are the causes of ‘vestibular’ mechanisms which include labyrinthine and eighth nerve pathology, leading to an asymmetry in vestibular afferents, and thus, the generation of a perception of instability/vertigo, and imbalance.

Ageing is a physiological process which occurs throughout life, and care should be taken not to attribute vestibular symptoms in the elderly to this process alone, although undoubtedly balance disorders are more common in the older age group, and complaints of dizziness and imbalance increase with age (Jonsson et al. 2004).

A plethora of morphological changes have been described in the vestibular organs and their neural pathways, including degeneration of the cristae ampullaris, degeneration of the maculae, hair cell alterations, otoconial changes, vestibular nerve degeneration, and degeneration of the central vestibular system (Bergstöm 1973; Engtröm et al. 1974; Nakayama et al. 1994). Physiological studies have demonstrated declining vestibular responses with increasing age, although there is poor correlation with anatomical changes (Peterka et al. 1990).

Neural degeneration within the central nervous system affects central integration of postural information, which becomes less efficient with age (Perrin et al. 1997). In addition, the musculo-skeletal system decreases in strength, and this together with neural delay results in balance impairments (Konrad et al. 1999). Many studies have demonstrated an increase in body sway in old age using posturography, and this is more marked in those who complain of balance disorders (Baloh et al. 1995). Normal ageing changes may impair overall balance but rarely give rise to acute dizziness, which depends upon an asymmetry of vestibular input. However, elderly people may decompensate from previously acquired vestibular disorders, for which they may compensate in their youth, but in old age these compensatory mechanisms are less efficient. Moreover, the elderly are prone to co-morbidity, the multi-sensory dizziness syndrome (Drachman and Hart 1972) and polypharmacy, any of which may compound disorders of balance (Luxon 1984).

The majority of vestibular disorders are due to peripheral labyrinthine or VIII nerve pathology (Table 15.1)

The commonest disorders in the adult population are benign paroxysmal positional vertigo, vestibular neuritis, and migrainous vertigo. A majority of neuro-otological units report 5 to 10 per cent of patients with vestibular symptoms suffering from central neurological involvement, while in studies of ‘dizzy patients’, approximately 75 per cent of patients suffer vestibular dysfunction, predominantly due to peripheral pathology, while 25 per cent suffer vestibular symptoms arising usually as a consequence of systemic pathology.

Benign paroxysmal positional vertigo was characterized by Dix and Hallpike in their seminal work in 1952 on patients with vertigo. The condition represents the single most common cause of vertigo in adults, and is characterized by brief but severe attacks of vertigo associated with nystagmus induced by changes in head position (Furman and Cass 1999; Parnes et al. 2003). The importance of diagnosis of this condition lies in its common occurrence, the ease of treatment with complete resolution of symptoms, and the differentiation of central positional nystagmus (Table 15.2).

Two pathophysiological mechanisms have been proposed to explain this condition: cupulolithiasis and canalithiasis. Both mechanisms depend on otoconia, calcium carbonate crystals embedded in the otolithic membranes of the utricle and saccule, which become free-floating within the vestibular system. They may become attached to the cupula of the semicircular canal, giving rise to a heavy ‘cupula’ or cupulolithiasis (Schucknecht 1969) or may float within the lumen of the canal, canalithiasis (Hall et al. 1979). Changes in head position cause movement of the heavy cupula, or allow the free-floating débris to fall under gravity through the narrow lumen of the canal and act as a plunger drawing the cupula behind it (Fig. 15.10). Either mechanism results in movement of the cupula, with stimulation of the hair cells of the cristae and resultant vertigo, together with nystagmus in the plane of the stimulated semicircular canal. In the vertical canals, the nystagmus is therefore vertical/torsional, while in the horizontal canal, the nystagmus is in the horizontal plane (Table 15.3).

The condition is most commonly idiopathic, and is more frequently observed in older patients (Baloh et al. 1987). It may also be associated with various inner ear pathologies, but is particularly common after head trauma, giving rise to labyrinthine concussion (Brandt 1999b). The condition may affect any of the three semicircular canals, but is most commonly associated with the posterior semicircular canal (Baloh et al. 1987; Baloh et al. 1993).

Characteristically, the patient complains of brief, severe episodes of vertigo induced by turning over in bed, tipping the head backwards to look at the sky, or reaching for something on a high shelf, i.e ‘top-shelf vertigo’. The diagnosis is made by the Dix Hallpike positioning test, with observation of characteristic features of paroxysmal symptoms (Fig. 15.11), which are currently considered to be explained most satisfactorily by the pathophysiological mechanism of canalithiasis outlined above. The observation of positional nystagmus may be the only abnormal clinical sign in a dizzy patient and thus the Dix Hallpike manoeuvre should therefore be performed routinely as part of the neuro-otological examination.

Treatment using a particle repositioning procedure (Section 15.6.3) is highly effective.

Acute vertigo associated with nausea and vomiting, but with no cochlear or neurological symptoms, is a common presentation in all age groups. The attacks are often unexpected and unprecipitated, but are commonly ascribed to a viral infection, and termed vestibular neuritis, vestibular neuronitis, or acute vestibulopathy. The term labyrinthitis is often preferred for a similar presentation with associated hearing loss. The evidence of underlying viral infection with total or subtotal loss of afferent vestibular input is usually circumstantial. A post-mortem study has identified selective neuronal loss in the vestibular ganglia and atrophy of the associated vestibular sensory epithelia, which would be consistent with a viral infection of the vestibular nerve (Baloh et al. 1996). In addition, viral DNA of herpes simplex type 1 has been detected in the superior and inferior vestibular ganglia, suggesting latent infection (Arbusow et al. 1999).

The majority of cases of vestibular neuritis affect the superior vestibular nerve (Fetter and Dichgans 1996; Aw et al. 2001), and it has been postulated that the superior division of the vestibular nerve travels through a bony canal, which is longer and narrower than that traversed by the inferior division, and thus renders it more susceptible to compression when inflamed. This hypothesis may explain the differential involvement of the superior rather than the inferior division in this condition (Goebel et al. 2001). Thus, it is frequently possible to obtain a normal saccular response,

as judged by vestibular evoked myogenic potentials, which depend upon normal inferior vestibular nerve function. In approximately 25 per cent of patients with vestibular neuritis, benign paroxsymal positional vertigo of the posterior canal variant may develop, and this would be compatible with preservation of the superior division of the vestibular nerve in those cases of inferior nerve vestibular neuritis.

The diagnosis of vestibular neuritis is a clinical diagnosis, based on the acute vestibular symptoms of vertigo, nausea, vomiting, and instability, which are exacerbated by head movement, but gradually abate over a period of one or two days. Within a period of two to three weeks, the majority of patients are rendered asymptomatic (Baloh 2003).

The acute symptoms of unilateral vestibular failure are accompanied by:

The vestibular system has been shown to be extremely adaptable, (Gonshor and Melvill Jones 1976), and symptomatic recovery occurs as a result of cerebral compensation. This process may be facilitated and expedited by physiotherapy intervention (Section 15.6.3).

Caloric testing in general reveals a canal paresis, which usually persists, despite recovery of symptoms, although recent work has demonstrated recovery of the caloric abnormality in up to 50 per cent of patients (Bergenius and Perols 1999; Schmid-Priscoveanu et al. 2001; Okinaka et al. 1993). Electronystagmography demonstrates unidirectional horizontal spontaneous nystagmus in all directions of gaze initially, but with recovery, first-degree nystagmus only, directed towards the unaffected ear will be observed in the absence of optic fixation and ultimately a directional preponderance of induced nystagmus or no abnormality will be found. Importantly, central vestibular abnormalities, such as abnormal vestibulo-ocular reflex suppression, deranged optokinetic responses or smooth pursuit, will not be observed although in the initial phase of the illness, a directional preponderance of optokinetic and induced nystagmus may be seen, because of the superimposition of spontaneous nystagmus upon the responses. In the absence of any central visuo-vestibular abnormality, or neurological signs, an MRI scan is not required.

In an acute unilateral peripheral vestibular disorder, assessment of the subjective visual vertical and horizontal shows a deviation from the true vertical or horizontal by 20° or more (Böhmer and Rickenmann 1995), while a normal subject can consistently adjust the light bar to within 2 to 3° of the true gravitational horizontal or vertical.

The differential diagnosis of vestibular neuritis involves the differentiation of hypothesized viral effects from a vascular event in the older patient and vascular risk factors should be evaluated. Labyrinthine infarction caused by occlusion of the internal auditory artery, may result in an acute vestibular syndrome, accompanied by hearing loss. Nonetheless, patients with acute vestibular lesions without hearing loss as a consequence of occlusion of branches of the internal auditory artery may mimic a vestibular neuritis (Kim et al. 1999).

From a neurological perspective, in the absence of a negative head thrust test, in which there are no catch-up saccades, and inability to stand with acute vertigo, cerebellar infarction should be considered. An MR scan should be performed in this clinical situation, as approximately a third of patients with this disorder will develop oedema with potentially fatal compression of the posterior fossa structures (Huang and Yu 1985; Iwase et al. 2001).

Migraine is the commonest neurological condition in the United Kingdom and is the commonest cause of dizziness or vertigo in children, and a common presentation, both with and without headache, of dizziness in adults. Symptoms of disequilibrium are reported in 50 to 70 per cent of migraineurs, and conversely, there is a high prevalence of migraine in patients presenting with vertigo (Savundra et al. 1997). The presentation of vertigo in association with migraine is very variable with episodes lasting seconds to hours, to prolonged instability lasting days (Dieterich and Brandt 1999).

Migraine, although a disorder characterized primarly by episodic headache, may be associated with a variety of different symptoms (Harker 1996; Silberstein 2004) (Section 18.2.1). While various types of presentation of migraine are described by the International Headache Society (2004), migrainous vertigo is not included in the criteria, but Neuhauser and Lempert (2004) have reviewed the topic extensively, and proposed criteria, which have been expanded by Brantberg and co-workers (2005).

The mechanism by which migraine gives rise to vertigo remains speculative (Furman et al. 2003), but hypotheses include complex interactions between the vestibular nuclei, trigeminal system, and thalamocortical processing centres, and a manifestation of a brainstem aura due to a spreading wave of neural depression. (Dieterich and Brandt 1999).

In cases of migrinous vertigo, there is frequently a family history of migraine, with troublesome motion sickness in childhood (Cutrer and Baloh 1992). In addition to vertigo, classical symptoms of sensory hyper-excitability may be present, including photophobia, phonophobia, and osmophobia. Some patients demonstrate vertigo as part of a migrainous aura and go on to develop a typical hemicranial headache, while others have vertigo that develops simultaneously with the headache, or appears after the headache phase. Most patients have attacks of vertigo unaccompanied by associated headache, and the picture is very similar to that of Menière’s disease, without auditory symptoms (Baloh 1997). There is acute onset, with severe vertigo, and frequently vomiting. Tinnitus and hearing loss are uncommon except with basilar migraine, making the differential diagnosis between this condition and Menière’s syndrome particularly difficult.

In young children, the manifestations of migraine are diverse and, commonly, headache is absent (Al-Twaijri and Shevell 2002). Presentations include cyclical vomiting, attacks of abdominal pain, ophthalmoplegia, and instability. Basser (1964) described an episodic disorder in young children under the age of 4 years, termed benign paroxysmal vertigo, which is characterized by the sudden onset of anxiety, crying, clinging to the parent, staggering, pallor, and vomiting. Typically the attack is brief, lasting only a few minutes, and the symptoms are exacerbated by head movement. Nystagmus and/or torticollis may be present. The child rapidly returns to normal, and although the attacks may occur several times a month under the age of 4 years, they gradually reduce in frequency and severity, disappearing by the age of 7 or 8 years. Frequently, these children develop classical migraine in adult life (Lanzi et al. 1994).

Review of the literature would suggest that benign recurrent vertigo described by Slater in 1979 represents a migrainous equivalent. Moreover, evaluation of patients with ‘vestibular Menière’s syndrome’ led to the conclusion that a significant percentage (approximately half) suffered vestibular migraine rather than Menière’s disease (Rassekh and Harker 1992). Diagnosis of migrainous vertigo remains difficult, as the diagnostic framework is based on a combination of the International Headache Society Criteria for Migraine, the presence of specific other symptoms, and the exclusion of other pathology (Neuhauser et al. 2001; Furman et al. 2003). There are no diagnostic clinical signs, nor vestibular test abnormalities.

About 1:1000 children are born with a significant hearing loss and, while this group have been extensively investigated in terms of auditory function, little attention has been paid to the associated vestibular dysfunction. Vestibular loss is now recognized as a feature of both genetic hearing loss and a number of syndromes associated with hearing impairment (Table 14.4). Children with congenital vestibular failure compensate extremely well, and the sole pointer to pathology may be delayed motor milestones.

In general recessively inherited hearing loss presents as congenital profound loss with, rarely, involvement of vestibular abnormalities, although vestibular dysfunction has been reported in DFNB2, 4 and 12 (Nance 2003). Dominantly inherited hearing loss is less severe, often progressive in adult life and may be associated with vestibular dysfunction in DFNA11 and DFNA9. The latter condition presents with a late onset, progressive hearing loss, together with vestibular failure and may mimic the clinical presentation of Menière’s syndrome (Fransen et al. 1999). X-linked hearing loss may also be associated with total vestibular failure and this finding corresponds with novel radiologic abnormalities. (Fig. 15.12) (Phelps et al. 1991).

A wide range of inherited syndromes are associated with auditory and vestibular dysfunction. Usher syndrome is characterized by sensorineural hearing loss and retinitis pigmentosa. Clinically three forms are recognized:

However, recent genotypic, phenotypic studies have shown that the differentiation of Usher types is not as clear-cut as proposed clinically (Kremer et al. 2006).

The Jervell and Lange-Nielsen syndrome, which is characterized by a long QT interval on electrocardiogram is recessively inherited and demonstrates both congenital, auditory, and vestibular failure, together with cardiac defects. Diagnosis is essential in the early years of life to prevent sudden cardiac death from dysrhythmia.

Pendred syndrome is an autosomal recessive disorder characterized by congenital deafness and goitre. Dilated vestibular aqeducts with or without a Mondini-like deformity of the cochlea (Fig. 15.13) have been described, and the condition is reported to occur with normal and abnormal vestibular function (Luxon et al. 2003).

CHARGE syndrome is characterized by Coloboma, Heart Anoma-lies, coanal atrisia, Retardation of growth and development, and

Genital and Ear anomalies. The disorder is an autosomal dominant condition with genotypic heterogenarity. The underlying genetic abnormality is a mutational deletion of the chromodomain helicase DNA-binding protein-7 CHD7 gene in the majority of cases. CT scan of the temporal bone demonstrates partial or complete semicircular canal hypoplasia, and characteristically, children have late motor milestones (Morimoto et al. 2006).

Mitochrondrial diseases are a clinically heterogenous group of disorders that give rise to dysfunction of the mitochondrial respiratory chain. Mitochrondrial mutations have been associated with syndromic and non-syndromic hearing loss (Xing et al. 2007), with limited reporting of vestibular function. However, vestibular loss has been reported in Kearns Sayre Syndrome (Weidauer and Lenarz 1984;), large deletions of the mitochondrial genome (Zeviani et al. 1990) and children with mitochrondrial disease (Lenard et al. 1992).

Menière’s disease is a clinical diagnosis based on the classic triad of fluctuating hearing loss, tinnitus, and vertigo (Menière 1861). It may occur at any age, but most commonly the initial presentation occurs between the ages of 30 and 60 years. It is rare both in children and in those over the age of 60 years. There is a family history in approximately 10 per cent of patients (Paparella and Djalilian 2002). The literature abounds with controversy on all aspects of this disorder, and the diagnosis should be based on the strict American Academy of Otolaryngology Head and Neck Surgery Committee on Hearing and Equilibrium Guidelines (1995).

The underlying pathophysiological mechanism is postulated to be overproduction or malabsorption of endolymph, resulting in endolymphatic hydrops or hypertension (Fig. 15.14). The underlying trigger has not been defined, but genetic, autoimmune, and environmental factors have all been postulated (Minor 2004). Menière’s attacks are considered to be the result of intermittent ruptures of the membranous labyrinth, with leakage of potassium-rich endolymph into the perilymph. The initial irritative phase of the attack is attributed to excitation of the hair cells by the increased potassium concentration around their basal surfaces, while the subsequent paretic phase is thought to result from a blockade of neurotransmitter release. Closure of the rupture is thought to allow recovery, with return of the normal chemical composition of the endolymph and perilymph (Tonndorf 1983).

Endolymphatic hydrops has also been documented in a variety of internal ear conditions, including syphilis, mumps, Cogan’s syndrome, trauma, chronic suppurative otitis media, and congenital ear disease. In this latter condition, longstanding hearing impairment is accompanied by the onset of acute vestibular episodes characteristic of Menière’s disease. This condition is sometimes called Menière syndrome, secondary Menière disease, or delayed endolymphatic hydrops (Schuknecht et al. 1990; Harcourt and Brooks 1995).

The clinical presentation of Menière’s disease is characteristically one of vertiginous attacks lasting for 1 to 8 hours, with tinnitus, hearing loss, and fullness in one ear, and this latter symptom may precede and outlast the acute vertigo. There is profound nausea and vomiting. Both vestibular and cochlear symptoms develop in approximately 60 per cent of those affected within six months of the onset of disease, although clinically it is not unusual to see a patient with fluctuating hearing loss or a single acute episode of dizziness unaccompanied by cochlear symptoms prior to the full-blown clinical presentation.

The episodes of vertigo tend to occur in clusters with intervals of freedom, and in the initial phase of the disorder both vestibular and cochlear symptoms recover, such that vestibular investigations and audiometry may be normal between attacks. However, as the disease progresses, a low-frequency sensorineural hearing loss is observed, and in an older patient with presbyacusis, the audiogram may assume a tent ‘shape’ (Fig. 15.15). With continuing progression, a plateau hearing loss emerges. Moreover, in the vestibular system, a canal paresis or caloric testing will be documented, with or without an accompanying spontaneous nystagmus or directional preponderance. With progressive attacks, interval disorientation and imbalance are common, as a result of fluctuating vestibular function with poor compensation. Some patients, especially in the later stages of the disease may develop drop attacks known as Tumarkin or otolithic crises (Ishiyama et al. 2001). In these attacks the patient drops to the ground without any warning, and frequently suffers injury. There may be a sense of being pushed to the ground by an external force, but frequently there is no associated vertigo, and no loss of consciousness.

The differential diagnosis of Menière’s disease includes perilymph fistula, vestibular neuritis with repeated decompensation, and vestibular migraine, which is a particularly difficult diagnosis to exclude, given the increased incidence of Menière’s disease in migrainous subjects and the increased incidence of migraine in patients with Menière’s disease (Kayan and Hood 1983; Neuhauser et al. 2001). Autoimmune inner ear disease may, in the early stages, mimic Menière’s disease, but progresses much more rapidly, leading to bilateral severe hearing loss and vestibular dysfunction within a relatively short time-span (Agrup and Luxon 2006).

Autoimmune inner ear disease may present as an isolated phenomenon or as part of a systemic autoimmune disorder (Broughton et al. 2004; Agrup and Luxon 2006). It is a rare, but important diagnosis, as rapid progressive, stepwise bilateral loss of auditory and vestibular function requires urgent medical treatment in an attempt to prevent or limit progression. Systemic autoimmune disorders with reported cochleo-vestibular involvement include polyarteritis

nodosa, Wegener’s granulomatosis, systemic lupus erythematosus, Behöet’s disease, and Cogan’s syndrome. The latter condition is particularly catastrophic with interstitial keratitis and acute sudden audiovestibular failure. As noted above, initial symptoms may mimic Menière’s disease, with fluctuation of hearing and ear pressure, but unlike this latter condition, the symptoms progress rapidly over weeks or months to involve both ears. Treatment requires high-dose steroids, with or without the addition of immunosuppressive drugs. A variety of immunosuppressive regimes have been evaluated, but whilst steroids may result in improvement of hearing loss, recent work has shown no significant benefit of methotrexate, and cyclophosphamide use is restricted by significant side effects (Ruckenstein 2004).

Damage to the vestibular apparatus may occur as a consequence of barotrauma, acoustic trauma, and physical trauma.

Over-exertion, scuba diving, and flying in unpressurized aircraft are common causes of otitic barotraumas (Luxon 1996), which, if sufficiently severe, may result in a perilymph fistula, with disruption of the oval or round window (Kohut et al. 1988). This leads to acute loss of hearing and vertigo, due to leakage of perilymph. Clinically, there may be a positive fistula sign, in which eye movement is induced in association with change in pressure in the external ear canal using a Segal’s speculum, with vertigo and nystagmus induced by pressure change in the external canal, or CSF as a result of coughing or straining.

Audiometry may show a sensorineural hearing loss, and electronystagmography may reveal peripheral vestibular nystagmus, with a canal paresis on caloric testing. However, the diagnosis of this condition is notoriously difficult and even observation at surgery may not be definitive. Management is conservative, with bed-rest, head elevation, and symptomatic treatment. Surgical exploration is indicated if symptoms persist, or there is a clear relationship of the onset of symptoms to trauma (Ludman 2003).

Acoustic trauma of sufficient intensity, for example an explosion, may rupture the tympanic membrane and give rise to a perilymph fistula. However, acoustic trauma in the form of hazardous occupational noise, gun-fire, or amplified music does not give rise to vertigo (Hinchcliffe et al. 1992) except in superior canal dehiscence.

Physical trauma to the head, with or without skull fracture, may give rise to three different clinical vestibular presentations:

Labyrinthine concussion with or without unilateral hearing loss is common after head injury of any severity (Davies and Luxon 1995). Acute vertigo with evidence of a canal paresis on caloric testing, and spontaneous nystagmus directed towards the unaffected ear, are common (Luxon 1996). The natural history of the disorder is characteristic of any acute unilateral vestibular loss, with gradual improvement in symptoms, but commonly, persistence of vestibular impairment on caloric testing. Benign paroxysmal vertigo may occur as a late consequence of labyrinthine trauma, some weeks or months after the head injury—a finding of particular importance in the medicolegal context. Associated central vestibular pathology or cerebellar dysfunction may preclude full recovery by vestibular compensation, with persistence of symptoms.

Dizziness or vertigo is reported in over three-quarters of patients with temporal bone fractures (Fig. 15.16) (Wennmo and Svensson 1989), although frequently other more serious neurological symptoms take priority. Thus with significant head injuries, vestibular

involvement may be overlooked. Longitudinal fractures, with involvement of the middle ear, tend to result in less severe vestibular symptoms associated with labyrinthine concussion. A conductive hearing loss is commonly present, and this may or may not be associated with a sensorineural loss (Luxon 1996). Positional vertigo is common. Transverse skull fractures frequently involve the labyrinth or internal auditory meatus, with profound permanent sensorineural hearing loss, and severe vertigo, nausea, and vomiting. The vestibular symptoms gradually improve as a result of cerebral compensation, providing there is no neurological dysfunction, while the hearing loss does not recover. Commonly this type of fracture is also associated with involvement of the facial nerve.

The labyrinth is supplied by the internal auditory artery, a branch of the anterior/inferior cerebellar artery (Fig. 15.17). Infarction of the internal auditory artery, therefore, commonly gives rise to profound auditory loss in addition to acute vestibular failure with vertigo and imbalance. The associated hearing loss suggests differentiation from acute vestibular neuritis, although the vestibular presentation may be very similar. Frequently there is associated infarction in the brainstem and/or cerebellum with preceding episodes of transient ischaemia within the vertebrobasilar circulation (Oas and Baloh 1992). Occasionally acute unilateral vestibular failure may occur in isolation and this has been attributed to occlusion of a branch of the internal auditory artery supplying the vestibular apparatus while sparing the cochlea. The diagnosis should be considered in older patients with vascular risk factors. Intra-labyrinthine haemorrhage may occur in patients with leading disorders, such as leukaemia (Schuknecht 1993).

Superior semicircular canal dehiscence is a disorder in which the bone between the apex of the superior semicircular canal and the middle cranial fossa is absent or attenuated (Fig. 15.18). The characteristic symptom associated with this anomaly is the Tullio phenomenon, in which vertigo and imbalance are precipitated by loud sound. However, Calvert’s sign, consisting of dizziness provoked by change in pressure in the external auditory canal, or Valsalva-induced vertigo, may also be associated with this condition (Minor 2005). Semicircular canal dehiscence is considered to be a congenital or developmental anomaly, as in many cases the abnormality is bilateral (Hirvonen et al. 2003), although the clinical presentation is often unilateral. The trigger for the unilateral presentation is

unknown, but it has been postulated that abnormally thin bone may be disrupted as the result of a traumatic injury.

Frequently, patients complain of dizziness and oscillopsia in response to sound at particular frequency and intensity, but the symptom may also be generated by coughing, sneezing, or straining. Commonly there is hyperacusis and an apparent air-bone gap, despite normal air conduction thresholds (Minor et al. 2003). Patients often complain of hearing themselves walk and swallow, and report a perception of rumbling or rustling in the ear.

The diagnosis is made by characteristic nystagmus, aligned to the plane of the dehiscent semicircular canal, in response to sound. The direction of the nystagmus may change depending on whether pressure is raised within the cerebrospinal fluid, for example by the Valsalva manoeuvre, or raised externally through the external auditory meatus. Diagnostically, vestibular-evoked myogenic potentials in response to clicks have also been shown to demonstrate a lower threshold in patients with superior canal dehiscence (Halmagyi et al. 2003b). Confirmation of the structural abnormality is made with high-resolution computerized tomography, with images reconstructed in a plane of the semicircular canal (Belden et al. 2003).

Bilateral vestibular failure may result from genetic abnormalities, meningitis, trauma, autoimmune disease, or most commonly ototoxicity (Bronstein et al. 1994). Most cases of acquired vestibular loss in childhood are associated with hearing loss, the commonest cause is pre, peri or postnatal infections with toxoplasmosis, herpes, cytomegalovirus, or rubella.

In adult-acquired vestibular failure, there is profound bilateral loss of afferent vestibular input, with postural imbalance, and ‘bobbing’ oscillopsia during head movements (Rinne et al. 1998). Aminoglycoside antibiotics are well-recognized to give rise to vestibular, or more rarely to auditory toxicity, but the effect is frequently not appreciated until the seriously ill patient begins to mobilize, and complains of dizziness, ataxia, and oscillopsia. The various antibiotics vary in their predilection for the auditory or vestibular system, but gentamicin is the most common culprit, with respect to the vestibular apparatus. Aminoglycoside antibiotics are not metabolized, but are excreted by glomerular filtration, and thus patients with renal impairment are at particular risk, with accumulation of the aminoglycoside in the blood and inner ear fluids. The ototoxic damage occurs in the hair cells of the inner ear, and may continue because of high levels of aminoglycoside in the inner ear fluids, even after the drug has been discontinued.

The diagnosis of bilateral vestibular failure can be clarified clinically by an inability to walk across a foam mattress with eyes closed, degradation of visual acuity with head movement, and by observation of catch-up saccades on the head impulse test (Halmagyi and Curthoys 1988). Confirmation of the abnormality, especially for medicolegal purposes, may be achieved by absent caloric responses, even with irrigation of the external auditory canals with ice-cold water, or water at 20°C for 1 minute, and by marked reduction or absence of vestibulo-ocular reflexes on impulsive rotation testing (Brandt et al. 1996a).

The differential diagnosis of bilateral vestibular failure requires consideration of a range of disorders. Postural imbalance is characteristically observed with both otological and neurological conditions, including severe unilateral vestibular failure, peripheral neuropathy, cerebellar disease, hydrocephalus, and extrapyramidal disorders such as progressive supranuclear palsy or Parkinson’s disease, while oscillopsia is common with central nystagmus syndromes such as vertical nystagmus, see-saw nystagmus, and periodic alternating nystagmus. However, these latter conditions are not particularly exacerbated by movement, unlike bilateral vestibular failure.

Tumours invading the petrous temporal bone and labyrinth are rare, but labyrinthine erosion with vestibular symptoms tends to be a poor prognostic sign. Malignant tumours include squamous cell carcinomas, arising in the external auditory meatus, middle ear, and mastoid in the elderly and aggressive primary temporal bone osteogenic sarcoma and chondrosarcoma in older children and young adults. Rhabdomyosarcomas are common in infants under 5 years, while metastatic temporal bone deposits are relatively common in adults.

Spontaneous labyrinthine fistula is almost always the result of bone erosion by cholesteatoma (Smith and Danner 2006), but rarely may be the result of syphilitic osteitis, tuberculous otitis media, chronic perilabyrinthine osteomyelitis or glomus vagale, and jugulare tumours. This is a life threatening situation, with acute vertigo, profound hearing loss. and the possible introduction of infection. Intralabyrinthine schwannoma are rare, but present with both hearing loss and vertigo. Detailed MR imaging allows diagnosis (Kennedy et al. 2004)

Viruses, bacteria, syphilis, and fungi may all give rise to inner ear pathology.

Labyrinthitis is an infection or inflammation of the labyrinth. Its symptoms are similar to vestibular neuritis, but additionally include sensorineural hearing loss. Three types are described: serous labyrinthitis, otogenic suppurative labyrinthithis, and meningogenic suppurative labyrinthitis. Serous labyrinthitis represents an irritation of the inner ear without bacterial or viral invasion. Toxins may spread into the inner ear as a result of otitis media or as a result of labyrinth surgery, from the middle ear through the round or oval window. Otogenic suppurative labyrinthitis involves bacterial invasion of the inner ear from contiguous areas within the temporal bone. Meningogenic suppurative labyrinthitis occurs when bacteria spread from the subarachnoid space into the inner ear during meningitis. A specific type of viral labyrinthitis is that caused by the mumps virus. The hearing loss resolves completely or partially in about 50 per cent of cases, while compensation brings about resolution of vestibular symptoms.

Viral infections may reach the inner ear via the blood stream, the meninges, the eighth nerve, or the inner ear. The evidence for viral infection in the inner ear is circumstantial. Westmore (1979) detected the mumps virus in the perilymph after sudden onset of hearing loss and changes in the otolith organs have been observed histologically in relationship to measles and mumps. In animals vestibular changes have been documented in infections of the inner ear with mumps, rubeola, measles, influenza A and B, cytomegalovirus and herpes simplex (Davis 1993). Thus, by extrapolation, it is considered that sudden vertigo may be caused by viral infections.

Acquired immunodeficiency syndrome is associated with both peripheral and central cochleovestibular symptoms, although hearing loss is more common than vertigo and balance. Vestibular changes have been demonstrated histologically (Pappas et al. 1995); antiviral agents have been reported to cause vertigo (Fantry and Staeker 2002); and opportunistic infections such as otosyphilis can give vestibular symptoms (Song et al. 2005).

Bacterial infection of the middle ear cleft is most commonly associated with chronic middle ear disease, which if erosive gives rise to a labyrinthine fistula with vertigo and sudden sensorineural hearing loss. This is a medical emergency with the risk of cerebral infection and abscess formation (Penido et al. 2005). Good public health and antibiotic therapy have significantly reduced the prevalence of these complications in developed countries, but complications of otitis media remain a serious problem in the Developing World.

Two acute bacterial infections are worthy of note: petrositis and malignant otitis externa. Both are aggressive disorders which may involve the inner ear and/or the eighth nerve. Petrositis is a perilabyrinthine infection which spreads to involve the apex of the petrous temporal bone. It may present as Gradenigo’s syndrome (1893) with otitis media with involvement of the trigeminal ganglion giving pain behind the ipsilateral eye, paralysis of the lateral rectus muscle, acute vertigo, and hearing loss.

Malignant otitis externa occurs in debilitated or immunosuppressed patients with Pseudomonas aeruginosa infection, which invades the surrounding tissues and gives rise to vertigo and hearing loss. Prolonged antibiotic treatment has improved the previously poor prognosis.

Otological syphilis is increasing in prevalence and 50 per cent of cases complain of vertigo and imbalance (Yimtae et al. 2007). The clinical course of the early acquired and late congenital forms of this condition are similar: sudden or rapidly progressive bilateral sensorineural hearing loss with mild vestibular symptoms (Garcia-Berrocal et al. 2006). Vestibular investigations in otosyphilis have demonstrated peripheral as opposed to central pathology and vestibular abnormalities were more marked in the congenital form of the infection (Wilson and Zoller 1981).

Aplasia or hypoplasia of the VIII nerve is a rare condition in children, but has been reported in 4 per cent of profoundly deaf children (Bamiou et al. 2001). If the vestibular nerve is involved, either in isolation or in association with hearing impairment, there may be delayed motor milestones, and frequently a syndromic diagnosis will be made. The VIII nerve can be reliably visualized on high-resolution MRI (Casselman et al. 1997).

Inherited VIII nerve disorders, with hearing loss and absent vestibular responses, have been reported in an autosomal recessive hereditary motor and sensory neuropathy (Butinar et al. 1999). Friedreich’s ataxia, is characterized by severe loss of both cochlear and vestibular neurons, but preservation of the sensory epithelia (Spoendlin 1974). Both auditory and vestibular neuropathy may be associated with peripheral neuropathy in olivopontocerebellar and spinocerebellar degenerations (Starr 2001) Cerebro-oculo-facial-skeletal syndrome is a rare autosomal recessive disorder in which dysmorphic features, hypotonia, osteoporosis, and neural degeneration are associated with accelerated cochlear and vestibular nerve degeneration (Fish et al. 2001). The vestibular nerve has been cited as abnormal in a range of inherited neurological disorders (Huygen and Verhagen 1994; Verhagen and Huygen 1994).

Compression of the VIII nerve in the internal auditory canal may be a consequence of osteopetrosis (Hanson and Parnes 1995) or craniodiaphyseal dysplasia (Himi et al. 1993). There is some controversy as to whether the VIII nerve is compressed in Paget’s disease, despite the common occurrence of vestibular symptoms (Khetarpal and Schuknecht 1990).

Vestibular neuritis (Section 15.3.1) A number of aetiologies have been postulated, but viral eighth nerve involvement is the preferred hypothesis (Strupp and Arbusow 2001).

The Ramsay–Hunt syndrome. The Ramsay–Hunt syndrome refers to a clinical presentation of herpes zoster oticus with facial palsy, auricular vesicular rash, hearing loss, and acute vertigo (Sweeney and Gilden 2001), which is now known to be caused by reactivation of the varicella zoster virus (Sections 20.2.2; 42.3.3). Abramovich and Prasher (1986) reported vertigo in 85 per cent of their series. The primary site of pathology remains unclear with studies having defined both labyrinthine and VIII nerve pathology (OMahoney and Luxon 1997). Recent work supports the use of steroids and acyclovir for prompt treatment and optimal outcome (Morrow 2000), although the presence of vertigo, diabetes mellitus, essential hypertension, and age were all negative prognostic factors (Yeo et al. 2006).

Bell’s Palsy. Vestibular dysfunction has been reported in Bell’s palsy or idiopathic facial palsy (Yagi et al. 1988; Watanabe and Suzuki 2006) (Section 20.2.3). A variety of mechanisms of vestibular dysfunction in Bell’s palsy have been postulated, including compression of the VIII nerve by an oedematous VII nerve, and involvement of both VII and VIII cranial nerves in the same viral process (OMahoney and Luxon 1997).

Lyme disease. Lyme disease is a tick-borne spirochaete infection with protean multisystem manifestations (Wormser 2006) (Sections 21.14.3; 42.5.2). Both auditory and vestibular symptoms may occur, and 12 per cent of patients have been reported to suffer dizziness (Lesser et al. 1990). Conversely, Rosenhall and colleagues (1988) studied 73 patients with vertigo and found serological evidence of Lyme disease in 14 per cent. Vestibular studies have identified both central and peripheral vestibular abnormalities, which have been interpreted as due to neurological and VIII nerve pathology (Ishizaki et al. 1993). Borrelia burgdorferi, the causative agent, is a particularly complex bacterium, which is frequently resistant to standard antibiotic regimes, and concern has been expressed about the need for better diagnosis and management of this disease (Stricker et al. 2006).

Meningitis. Vestibular loss occurs more commonly than deafness following bacterial meningitis, although the site of lesion, i.e labyrinth or VIII nerve, is unclear. Moreover, it may be difficult to distinguish infective from drug-induced vestibular damage in some cases. Rasmussen and colleagues (1991) have reported that of 94 people who survived pneumococcal meningitis, 9 suffered vertigo and 14 per cent demonstrated bilateral vestibular failure on formal vestibular assessment, 4 to 16 years after the illness, while Naess and colleagues (1994) found audiovestibular abnormalities in a similar number (14 per cent) who had suffered meningococcal meningitis one year previously. Post-meningitic vestibular loss in young children manifests as regression in motor milestones, although long-term follow-up into adulthood indicates that, although vestibular symptoms compensate very well, residual symptoms of imbalance may remain whilst walking in the dark (Hugosson et al. 1997). In adults and older children, poor balance and oscillopsia are the common complaints of vestibular failure. MR scan may indicate labyrinthitis ossificans of both the semicircular canals and the cochlea (Fig. 15.19). Other causes of basilar meningitis which may involve the VIII nerve include tuberculosis, cryptococcosis, and coccidioidomycosis (Baloh and Honrubia 2001).

Infarction. The vertebrobasilar circulation supplies the labyrinth, VIII nerve, vestibular nuclei, and vestibulo-cerebellar connections. Amarenco and Hauw (1990) have reported auditory and/or vestibular symptoms and signs in over half of patients with anterior inferior cerebellar artery territory infarction. Histologically, half of the patients had involvement of the VIII nerve, and in one this was the only abnormality. As this internal auditory artery arises from the anterior inferior cerebellar artery, this finding may be expected. Moreover, aneurysms on this vessel may also involve the VIII nerve (Porter and Eyster 1973).

Vascular loops. Neurovascular compression of the VIII nerve remains a controversial entity. The close relationship of a blood vessel to the VIII nerve on brain MRI does not prove the existence of a causative relationship, even in the presence of vertigo and auditory symptoms. This MRI finding has been reported in 12.5 per cent of otherwise normal scans (Parnes et al. 1990). Nonetheless, reports of improvement in ‘disabling’ vestibular symptoms and signs following VIII nerve microvascular decompression have been made (Jannetta et al. 1984). The term ‘vestibular paroxysmia’ has been coined to describe brief spells of vertigo, often attributed to vascular loops frequently provoked by head position and commonly controlled by carbamazepine (Brandt and Dieterich 1994).

Vascular compression syndromes. Basilar artery ectasia may give rise to VIII nerve symptoms as a consequence of compression or ischaemic events (Passer and Nuti 1996; Passero and Filosomi 1998). Moreover, bilateral vestibular failure has been reported in this condition (Nuti et al. 1996).

Cerebellopontine angle lesions and, in particular, acoustic neurinomas are a rare cause of vestibular symptoms. Despite the misnomer, acoustic neurinomas arise mainly on the vestibular division of the VIII cranial nerve. Vestibular schwannoma represents 6 per cent of intracranial tumours, with 13 newly diagnosed cases per million population per year (Sections 11.2 and 27.7.3). The most common presentation is of progressive unilateral hearing loss in 85 per cent, accompanied by tinnitus in 70 per cent and vertigo in 20 per cent (British Association of Otolaryngologists, Head and Neck Surgeons 2002). However, about half will complain of ‘imbalance’ (Selesnick et al. 1993). The clinical presentation is described in five stages (Ramsden 1997) (Table 15.4). As the tumour expands into the cerebellopontine angle, there is involvement of the V and VII cranial nerves, together with ipsilateral cerebellar signs and, ultimately, lower cranial nerve involvement.

While auditory, particularly auditory brainstem-evoked responses, and vestibular investigations are suggestive of the diagnosis, gadolinium-enhanced MRI is the gold standard investigation

(Zealley et al. 2000). Recent work has advocated conservative management (Smouha et al. 2005) with repeated follow-up scanning for small tumours, but gamma knife intervention and microsurgery may also be appropriate (Yamakami et al. 2003). Any rapid increase in size with signs of brainstem compression requires urgent surgical intervention.

Neurofibromatosis 1, von Recklinghausen’s disease or NF1, and neurofibromatosis 2 or NF2 are clinically and genetically distinct disorders (Gutmann et al. 1997; Mrugala et al. 2005; Yohay 2006) (Section 11.2). Autosomal dominant NF2 is due to loss of function of a tumour-suppressor gene on 22q12, whilst the NF1 gene is located on chromosome 17q11.2. Management options include expectant policy, with interval scanning, surgical removal, and stereotactic radiosurgery/radiotherapy. The decision regarding management depends on age, tumour size, health status, patient preference, and surgical considerations, but the benefits of each treatment option remain ill-defined (British Association of Otolaryngologists, Head and Neck Surgeons 2002). Postoperatively, vestibular rehabilitation physiotherapy frequently improves postural stability and the perception of disequilibrium (Herdman et al. 1995), but vestibular symptoms persist in about one-third of cases postoperatively (Driscoll et al. 1998). The differential diagnosis of cerebellopontine angle lesions includes meningiomas, lipomas, haemangiomas, granulomas, and hamartomas (Ramsden 1997).

Metastatic carcinoma in the temporal bone is uncommon, but the internal auditory canal is the second most common site for temporal bone metastases, from primary lesions of the breast, lung, kidney, stomach, larynx, prostate, and thyroid gland (Streitmann and Sismanis 1996). Moreover, cochlear and vestibular symptoms have been reported in 10 per cent of patients with carcinomatous meningitis (Alberts and Terrence 1978).

Paraneoplastic syndrome. The non-metastatic complications of carcinomatous encephalomyelitis may involve the vestibular nerve (Gulya 1993). Almost all tumours have been associated with non-metastatic complications, but small cell carcinoma of the lung is most common. The presence of antineuronal antibodies provides a diagnosis and directs the search for the primary tumour.

Audiovestibular problems are commonly associated with neural involvement in sarcoidosis. Five per cent of patients with sarcoidosis develop a granulomatous meningitis, which directly infiltrates the cranial nerves (Section 36.4). The VIII nerve is the fourth most commonly affected and vestibular symptoms may be the first manifestation of neurosarcoidosis (Jahrsdoerfer et al. 1981) Steroid treatment may improve audiovestibular symptom, provided it is commenced before permanent damage ensues (Brihaye and Halame 1993).

Involvement of the VIII nerve has also been reported in Hashimoto’s disease and rheumatoid arthritis (Stephens 1970), but the site of vestibular symptoms remains poorly clarified in the many systemic autoimmune disorders in which vestibular symptoms have been reported.

Central vestibular disorders, which include developmental, ischaemic, degenerative, neoplastic, traumatic, or infective and inflammatory pathologies, present with distinct clinical neurological, and oculo-motor signs, which provide accurate indicators for site of lesion diagnosis.

Disorders of the craniocervical junction. Pathology at the cranio-cervical junction can give rise to brainstem and lower cranial nerve symptoms, including vertigo, hearing loss, tinnitus, swallowing difficulties, hoarseness, and rarely airway obstruction. Such symptoms may result from brainstem compression, stretching of the lower cranial nerves or vertebrobasilar ischaemia.

The Arnold Chiari malformation is a developmental abnormality in which the brainstem and cerebellum are elongated downwards into the cervical canal (Fig. 15.20) (Section 9.3). The less severe Chiari type presents in adult life and is characterized by oscillopsia, associated with downbeat nystagmus, and gait unsteadiness (Plaza Mayor et al. 2006). In addition, cough headache is a common symptom and lower cranial nerve palsies, including hearing loss, and both gait and limb ataxia are typically noted on examination. Diagnosis is by means of MR scanning. Sub-occipital decompression of the foramen magnum may alleviate progression of the neuro-otological abnormalities, but rarely brings about symptomatic improvement (Cristante et al. 1994). Recent work has suggested a genetic basis for this condition (Boyles et al. 2006). The more severe Chiari type II malformation commonly presents in the first few months of life and is associated with hydrocephalus, spina bifida, and other nervous system malformations (Stevenson 2004).

Syringomyelia and syringobulbia. Syrinx formation in the brainstem is commonly associated with Arnold Chiari type I malformations and syringobulbia describes the extension of the syrinx into the brainstem. The precise symptoms and signs depend on the course of the syrinx, but commonly patients present with involvement of the lower cranial nerve nuclei, particularly the XII nerve and descending tract and nucleus of V (Aryan et al. 2004). Symptoms include atrophy and fasciculations of the tongue, together with loss of pain and temperature sensation in one or both sides of the face. Dysphonia and dysphagia are common with involvement of the IX and X nerve nuclei. Central positional nystagmus is a characteristic finding (Thrush and Foster 1973) and may be the only abnormal neurological sign.

Basilar impression is an upward indentation or invagination of the rigid cervical spine into the convex skull base (Goel et al. 1998), with intracranial projection of the odontoid compressing the medulla and the cerebellum being compressed posteriorly by the upper cervical vertebrae. A similar acquired presentation may be seen in the elderly in Paget’s disease, and more rarely, it may also occur with rheumtaoid arthritis, osteomalacia, osteogenesis imperfecta, cretinism, and rickets (Menezes et al. 1980).

Abnormalities of the cranio-cervical junction are diagnosed by imaging. Basilar impression is confirmed on lateral radiography of the skull with the tip of the odontoid peg extending above Chamberlain’s line, a line drawn from the posterior edge of the hard palate to the posterior lip of the foramen magnum. MRI defines the presence of syringobulbia.

Spinocerebellar ataxias. The hereditary cerebellar ataxias (Chapter 39) are a heterogenous group of inherited degenerative disorders in which the cerebellum is primarily involved, together with its afferent and efferent connections (Schöls et al. 2004). With advances in genetics, the spinocerebellar ataxias, SCA, which are included in this category are numbered according to the order in which the associated genetic abnormalities were identified. About one-third of the spinocerebellar ataxias are inherited as autosomal dominant disorders and present with gait ataxia, dysarthria, dysphagia, dysmetria, and intention tremor (Schöls et al. 1997). The brainstem and spinal cord, together with the basal ganglia, peripheral nerves, optic nerve, retina, and cerebrum may also be involved in specific syndromes.

Neuro-otologically, auditory and vestibular symptoms are common in many of the hereditary spinocerebellar ataxia syndromes, though cerebellar findings frequently overshadow the loss of vestibular function. Vertigo is frequently not a feature of the progressive cerebellar ataxias as vestibular function is lost slowly, progressively, and symmetrically, but is a common feature of the episodic ataxia syndromes. Oculomotor abnormalities are common (Burk et al. 1999) and a detailed examination of eye movements may allow identification of the phenotype prior to genetic testing (Buttner et al. 1998). Cerebellar eye movement abnormalities, including failure of smooth pursuit function and suppression of the vestibular oculo-reflex with optic fixation, frequently give rise to head movement induced oscillopsia. This latter symptom may also be consequent upon bilateral vestibular failure (Rinne et al. 1998). A variety of forms of central pathological nystagmus are observed with these conditions, including bidirectional gaze evoked nystagmus, vertical nystagmus, both upbeat and downbeat, rebound nystagmus, and central positonal nystagmus (Table 15.2).

Specifically, patients with SCA6 may present with spontaneous vertigo that pre-dates the onset of ataxia and may be responsive to treatment with acetazolamide (Jen et al. 1998). This condition may also present with downbeat nystagmus (Takahashi et al. 2004) and periodic alternating nystagmus (Hashimoto et al. 2003). In SCA1 and SCA2, saccades are often dysmetric, but may also be abnormally slow (Buttner et al. 1998). In SCA3 there may be a progressive supranuclear ophthalmoplegia. Bilateral vestibular failure has been documented in SCA1 (Buttner et al. 1998) and SCA3 (Gordon et al. 2003).

Friedreich’s ataxia is the most common hereditary ataxia and is autosomal recessive (Section 39.4.1). It is characterized by progressive ataxia, sensory loss, and muscle weakness often with scoliosis, pes cavus, and heart disease (Friedreich 1863). The phenotypic expression of Friedreich’s ataxia shows marked intra- and inter-familial variability (Montermini et al. 1997). Auditory (Section 14.3.2) and vestibular loss are common features (Ell et al. 1984), particularly in the later stages of the disease. Oculomotor findings characteristically include saccadic dysmetria, ocular flutter, and square wave jerks. A variety of other eye movement disorders are reported (Bhidayasiri et al. 2005; Spieker et al. 1995). The episodic ataxias together with SCA6 are channelopathies associated with mutations in ion channel genes (Cannon 2006). They are characterized by attacks of ataxia, beginning in early childhood or adulthood, with essentially normal neurological function in between the acute episodes (Baloh and Jen 2000). Episodic ataxia type II is commonly associated with acute episodes of vertigo, nausea, and vomiting, associated with marked unsteadiness, and with the progression of time, interval nystagmus and cerebellar eye movement abnormalities are observed (Baloh et al. 1997). The disorder is responsive to acetazolamide and valproic acid (Scoggan et al. 2006).

The peripheral vestibular system and central vestibular connections in the brainstem and cerebellum are supplied by the vertebrobasilar system (Fig. 15.21). Ischaemia in this territory frequently results in vestibular symptoms as the vestibular nuclei, which occupy a large area in the lateral zone of the brainstem (Gillilan 1964),are particularly susceptible to a reduction in the blood flow of the main basilar artery. Thus, vertigo or dizziness has been reported as the first and most frequent symptom of vertebrobasilar insufficiency and may occur, not only due to primary vertebrobasilar disease, but also as a result of hypotension, cardiac arrhythmia, or cerebral vasospasm.

Transient vertebrobasilar ischaemia. In 1955, Millikan and Siekert proposed a definition of vertebrobasilar insufficiency: ‘a state of transient decrease in the cerebral blood flow, without actual infarction resulting in transient inability to meet the metabolic requirements of the brain’. Episodic vertigo and oculomotor abnormalities are the commonest early symptoms of reduced blood flow in the vertebrobasilar territory (Williams and Wilson 1962). Transient ischaemia gives rise to brief episodes of vertigo, usually of a few minutes’ duration and is associated with one or more of the constellation of brainstem symptoms and signs characteristic of ischaemia in the posterior circulation (Grad and Baloh 1989). By definition, symptoms and signs associated with transient

ischaemic attacks are of less than 24 hours duration. Recurrent vertigo unassociated with additional neurological symptoms should not be diagnosed as ischaemic events (Fisher 1967; Luxon 1990).

The commonest cause of basilar insufficiency is atherosclerosis of the subclavian and vertebral or basilar arteries. Dissection, arteritis, emboli, polycythaemia, and hyperviscosity syndromes may also present in this way. It must be emphasized that whilst cervical spondylosis is common in older patients, mechanical compression of the extracranial vertebral artery is extremely rare in this condition (Baloh and Honrubia 2001). In transient ischaemic attacks MRI is frequently normal, but may show evidence of old infarcts, or diffuse cerebrovascular disease.

Occlusion of the vertebral artery associated with voluntary turning of the head is known as Bow Hunter’s stroke and is an extremely rare cause of vertebrobasilar ischaemia. A recent review has highlighted the success of vertebral artery decompression (Netuka et al. 2005). Unlike benign paroxymal positional vertigo, in this condition, vertigo is not positional, but is precipitated in the upright position by turning the head to right or left.

Total occlusion or stenosis of the subclavian or innominate artery may give rise to the disorder known as the subclavian steal syndrome, which occurs in 3 per cent of patients with vertebrobasilar syndromes. Occlusion of the proximal subclavian artery results in reversal of blood flow in the vertebral artery, which then acts as a collateral to the upper limb, and blood is siphoned from the vertebrobasilar system into the distal subclavian artery to maintain adequate blood flow during exercise (Taylor et al. 2002). This diagnosis should be considered when claudication or fatigue of the upper limb is accompanied by vertigo and other vertebrobasilar symptoms, although vertigo may be the sole symptom (Wheeler and Vincent 1980). A systolic bruit in the supraclavicular fossa and a disparity of blood pressure between the two arms are the characteristic physical signs of this disorder and surgical intervention is highly effective (Smith et al. 1994).

Strokes.A stroke, by definition, involves a neurological deficit present for more than 24 hours or leads to death (Warlow et al. 2003). It may be consequent upon infarction or haemorrhage, and vertigo with or without hearing loss may be the main clinical presentation (Murakami 2006).

Brainstem/cerebellar infarctionBrainstem and cerebellar infarction may be the consequence of primary atherosclerotic disease in the vertebrobasilar territory (Vilela and Goulao 2005). It is seen also with vertebral artery dissection, and is often traumatic in origin, for instance associated with chiropractic neck manipulation (Saeed et al. 2000). Infarction may also occur as a result of small vessel disease with involvement of the deep perforating arteries of the vertebrobasilar circulation. Embolism may also give rise to brainstem or cerebellar infarction as a consequence of cardiogenic embolism, often associated with dysrhythmias such as atrial fibrillation (Hart et al. 2000), more proximal artery occlusion (Caplan et al. 1992) or paradoxical embolism from a patent foramen ovale (Mas 2003). Brainstem infarction may occur with or without cerebellar involvement as a consequence of the excellent collateral circulation of the major cerebellar arteries (Amarenco 1991). Brainstem and cerebellar haemorrhage are commonly associated with hypertension, but may be seen in association with arteriovenous malformations, coagulopathies, cavernous angiomas, aneurysms, or tumours (Sutherland and Aurer 2006).

Vertigo is a common presenting feature of both brainstem and cerebellar infarction and may be associated with profound nausea, vomiting, and gross postural imbalance with inability to stand or sit. The accompanying symptoms and signs allow differentiation between posterior/inferior cerebellar artery syndrome, anterior inferior cerebellar syndrome, or Wallenberg’s syndrome (Section 2.4.4), and superior cerebellar artery infarction.

Lateral medullary infarction.The Wallenberg or lateral medullary syndrome has been ascribed to occlusion of the posterior inferior cerebellar artery, although Fisher (1967) has reported that it is more commonly associated with primary occlusion of the ipsilateral vertebral artery (Fig. 15.22). In young adults, traumatic aortic dissection should be considered (Frumkin and Baloh 1990). The patient presents with sudden onset vertigo, nausea, vomiting, severe imbalance, ipsilateral facial numbness and weakness, diplopia, dysphagia, and dysphonia. There is a motor disturbance which causes both a tendency to deviate towards the site of the lesion, as if pulled by a strong external force, and excessively large voluntary and involuntary saccades directed towards the site of the lesion with hypermetric saccades directed away from the lesion (Kommerell and Hoyt 1973).

In addition, there is an ocular tilt reaction with ipsilateral head tilt, the ipsilateral eye being lower than the contralateral eye and ocular torsion with the upper pole of the eye rotated towards the site of the lesion. On neurological examination, there is an ipsilateral dissociated sensory loss in the distribution of the facial nerve, with contralateral truncal loss, and ipsilateral cerebellar ataxia, bulbar palsy, and Horner’s syndrome.

Lateral ponto-medullary infarction. The anterior inferior cerebellar artery syndrome, or lateral ponto-medullary infarction (Oas and Baloh 1992) is also characterized by vertigo. However, as the labyrinthine artery arises from the anterior inferior cerebellar artery, infarction of the membranous labyrinth is commonly associated with this condition. Thus, distinguishing between the lateral medullary syndrome and the lateral ponto-medullary syndrome characteristically depends upon the profound unilateral hearing loss in the latter as a result of infarction of the labyrinth, VIII nerve or VIII nerve root entry zone (Table 15.5). Neurological signs include unilateral facial paralysis, cerebellar ataxia and ipsilateral loss of pain and temperature sensation on the face due to involvement of the trigeminal nucleus and tract, together with a contralateral decrease in pain and temperature sensation on the body, due to involvement of the crossed spinothalamic tract.

Cerebellar infarction. Cerebellar infarction may be confused with acute peripheral labyrinthine dysfunction, as the presenting symptoms may be primarily vertigo, vomiting and ataxia, without brainstem signs (Rubenstein et al. 1980; Huang and Yu 1985). The diagnosis should be considered in all patients under 50 years presenting with acute dizziness and headache (Savitz et al. 2007). The distinction between these two conditions lies in the severe truncal ataxia and direction changing gaze evoked nystagmus associated with cerebellar infarction. The presence of downbeat nystagmus localizes pathology to the caudal midline cerebellum.

The three main cerebellar arteries, the posterior inferior, anterior inferior, and superior, supply branches to the brainstem near their origin and form a rich anastomotic network across the surface of the cerebellum. Thus, occlusion of any of these arteries near their origin may result in only brainstem infarction with sparing of the cerebellum. However, more distal pathology gives rise to a cerebellar infarction, which may give rise to progressive symptomatology as a consequence of swelling and compression of the brainstem or may produce hydrocephalus (Sypert and Alvord 1975) with fatal consequences. Urgent medical or surgical intervention is required (Jensen and St Louis 2005).

Brainstem and cerebellar haemorrhageAcute sudden onset vertigo with severe headache may be a prodrome for brainstem (Barinagarrementeria and Cantu 1994) or cerebellar haemorrhage (Elkind and Mohr 1997) associated with hypertension in approximately two-thirds of patients. Although vertigo may be the presenting symptom, there is frequently a rapid deterioration characterized by coma, flaccid quadriplegia, loss of horizontal eye movements, pin point reactive pupils, and ocular bobbing in pontine lesions with rapid cardio-respiratory failure and death in medullary lesions.

Cerebellar haemorrhage deserves particular mention as accurate diagnosis, together with neurosurgical intervention may be life-saving (Jensen and St Louis 2005). Like cerebellar infarction the diagnosis may be confused with acute peripheral vestibulopathy, but the distinguishing features include nucal rigidity and prominent cerebellar signs, together with ipsilateral, facial, and gaze paralysis. Midline cerebellar haemorrhage may be particularly difficult to diagnose, but a characteristic feature is profound inability to stand, which is never associated with peripheral vestibulopathy. Without surgical intervention the prognosis is poor with 50 per cent of patients losing consciousness within 24 hours and 75 per cent becoming comatose within one week.

Imaging is essential to define pathology and should be carried out in any patient with a presentation atypical of a peripheral vestibulopathy CT scanning is superior to MRI for identifying intraparenchymal blood. Any patient therefore who presents with evidence of cerebellar involvement and vertigo should undergo a CT scan and if this is negative, an MR scan (Amarenco et al. 1993). Imaging may also allow delineation of the intra- and extra-cranial circulation in order to identify focal vascular lesions (Vilela and Goulao 2005).Vertebral artery dissection may be identified by the presence of haemosiderin the wall of the vertebral artery, on fat saturated T1 weighted MR images of the neck, while Doppler studies may be useful for demonstrating reversal of blood flow in the vertebral artery in patients with subclavian steel syndrome. MR angiography is of value in assessing the vertebrobasilar circulation, but formal angiography is indicated with severe transient ischaemic attacks without obvious risk factors or in posterior circulation ischaemic events following trauma or neck manipulation. Notwithstanding this, the main risk of contrast angiography is infarction within the distribution of the injected vessel (Sections 3.2.2 and 5.5.5).

Multiple sclerosisMultiple sclerosis is a degenerative disease, in which plaques of demyelination are scattered in time and space throughout the central nervous system (Section 37.5). The demyelination is confined to central nervous system myelin, and therefore plaques involving the vestibular (Gass et al. 1998) and auditory root entry zones may present with sudden hearing loss or vertigo (Commins and Chen 1997). Vestibular symptoms are common and may be the presenting feature (Grenman 1985; Rae-Grant et al. 1999).

Acute vertigo may present in up to 5 per cent of cases of multiple sclerosis, but may occur at some point in the disease in up to 50 per cent (Grenman 1985). Hearing loss (Section 14.3.2) occurs in about 10 per cent of patients and commonly presents as an acute unilateral loss with gradual recovery, while midline brainstem plaques may give rise to bilateral loss and more proximal plaques may give rise to auditory processing dysfunction (Section 14.3.3). Multiple sclerosis may mimic acute vestibular neuritis or labyrinthitis and should be included in the differential diagnosis of these conditions (Sasaki et al. 1994; Thomke and Hopf 1999).

The clinical presentation varies depending on the distribution of cerebral lesions, but brainstem and cerebellar symptoms and signs are common, in addition to optic atrophy secondary to optic neuritis. Oculomotor findings are almost the rule (Alpini et al. 2001) and disordered pursuit, hypermetric saccades, and a range of central nystagmus, including bidirectional gaze evoked, rebound, periodic alternating, vertical, torsional, see-saw ataxic nystagmus, internuclear ophthalmoplegia, and pendular nystagmus have all been reported in multiple sclerosis, with the latter two conditions being particularly suggestive of this diagnosis. Positional vertigo and central positional nystagmus are common in multiple sclerosis particularly with plaques in the floor of the fourth ventricle (Buttner et al. 1999).

The gold standard for diagnosis is T2-weighted MRI showing characteristic white matter plaques in approximately 95 per cent of patients (Pyhtinen et al. 2006). Clinical examination may reveal a diversity of signs including involvement of the pyramidal tracts, cerebellum, and sensory tracts, but characteristically patients will demonstrate addition oculomotor abnormalities, for example, internuclear ophthalmoplegia, bidirectional gaze evoked nystagmus, central positional nystagmus, together with disordered pursuit, optokinetic responses, and saccades, with the exact abnormalities depending upon the site of lesions within the brainstem and cerebellum.

Dizziness and/or vertigo are early or initial symptoms in 25 per cent of brainstem tumours. In later life, metastases are the most common neoplasms involving the brainstem and/or cerebellum, which give rise to vestibular dysfunction. Brain-stem lesions typically present with progressive cranial nerve palsies together with long tract signs, while midline cerebellar lesions give rise to truncal ataxia and oculomotor abnormalities, including impaired smooth pursuit, saccadic dysmetria, and rebound nystagmus. Hemispheric cerebellar lesions cause ataxia of the ipsilateral limbs, with truncal ataxia. Infratentorial tumours account for 60 to 70 per cent of intrinsic brain tumours in children and present with gait abnormalities, ataxia, dizziness, cranial nerve palsies, symptoms of increased intracranial tension, irritability, and decline in school performance. Temporal lobe tumours give rise to ‘disequilibrium’ more frequently than in any other cortical site. This is not surprising given that the temporal lobes exert a modifying influence upon the vestibular nuclei.

Middle ear infections can give rise to life-threatening intracranial complications including extradural abscess, subdural abscess, sigmoid sinus thrombosis, meningitis, brain abscess and otitic hydrocephalus and in about one third of patients there are multiple complications within this group (Ludman 1997). Meningitis remains the most common complication, but in all complications imbalance or vertigo are overshadowed by fever, headache, vomiting and frequently drowsiness.

Post-traumatic vertigo is most commonly the result of a head injury, whiplash injury, or more rarely barotrauma. With mild head injuries, dizziness is reported to occur within one week in 53 per cent (Levin et al. 1987), but persists for at least two years in 18 per cent (Cartlidge 1978). In some patients dizziness and imbalance may remain intrusive for more than 4 years after injury (Edna and Cappelen 1987). The relevance of these figures lies in the very high percentage of the population in civilized societies suffering head injury and reports of even mild or moderate head injury (Davis and Luxon 1995) giving rise to significant disability, with a significant number of injured people failing to return to their pre-accident or equivalent level of work within 5 years (Eide and Tysnes 1992; Berman and Fredrickson 1978).

Blunt head injury is the commonest cause of post-traumatic vertigo and recent radiographic classification of otic capsule violating fractures versus otic capsule sparing fractures has enabled the prediction of temporal bone complications, including facial nerve injury, labyrinthine involvement, and cerebrospinal fluid otorrhoea (Little and Kesser 2006). In general, pathology disrupting the otic capsule gives rise to profound sensorineural hearing loss and vestibular failure, while fractures that do not encroach upon the otic capsule give rise to vestibular symptoms as a consequence of labyrinthine concussion, perilymph fistula, and canalolithiasis (Section 15.3.2). In major head injury, post-traumatic vertigo is frequently overshadowed by other more life-threatening neurological abnormalities. Evidence of the skull fracture should be sought, progressive ecchymoses of the mastoid region, the Battle sign, may be associated with longitudinal fractures extending into the mastoid region. In this group of patients, dizziness or vertigo has been reported in up to 93 per cent (Wennmo and Svenson 1989). With transverse fractures there is commonly involvement of the VIII cranial nerve with severe vertigo, nausea, vomiting, and profound hearing loss. Vestibular symptoms tend to be less dramatic with longitudinal fractures in which laceration of the tympanic membrane with cerebrospinal fluid or bloody otorrhoea or haematympanum give rise to a conductive hearing loss. Neurologically, cerebral concussion is commonly associated with dizziness and vertigo, and a detailed vestibular investigation is required to differentiate the underlying pathology (Ernst et al. 2005; Luxon 1996). Six weeks after cerebral concussion approximately 50 per cent of patients have totally recovered but the remainder complain of symptoms and 14 per cent report dizziness (Rutherford 1977). Psychosocial factors are important in the persistence and severity of symptoms (Fenton 1996).

Whiplash injury describes the mechanism of hyper-extension, followed by flexion of the neck. Imbalance, including vertigo, is second only to cervical pain and headache following whiplash injury and is reported in up to 85 per cent of patients following rear-end road traffic accidents (Oosterveld et al. 1991). The symptoms of whiplash injuries develop rapidly and within 24 hours of injury, 93 per cent of patients present with neck pain. Hence, dizziness presenting weeks or months after injury is unlikely to be the consequence of the injury—an important medicolegal consideration. The mechanism of vertigo following whiplash injury is unclear, but a variety of mechanisms have been suggested (Luxon 1996) to explain the presence of both peripheral and central vestibular abnormalities on formal neuro-otological testing, including injuries to cervical muscles and discs (Endo et al. 2006), involvement of cervical sympathetic nerve supply and cervical nerve roots, damage to the otolith organs, brainstem damage, spinal cord contusion/haemorrhages, and alterations in blood flow.

Vertigo may present as an aura of epilepsy (Gowers 1907), or as part of a temporal lobe seizure, but has also been identified with other forms of epilepsy (Lennox 1960; Schneider et al. 1968). Individual cases are reported throughout the literature, but relatively little advance has been made in the inter-relationship of the phenomenon for a number of reasons: the absence of pathophysiological data, the vague description of the patient’s symptoms and the lack of objective electrophysiological recordings contemporaneous with the vertigo. (Brandt 1999a). Smith and Docherty (1982) reported a case of temporal lobe epilepsy with oscillopsia and nystagmus, Furman and coworkers (1990) described a woman with episodic ataxia and nystagmus in association with EEG changes in the temporo-parietal region and more recently Kluge and colleagues (2000) reported a 5-year-old boy with left frontocentral onset of epileptic discharges accompanied by complaints of vertigo. Thus epileptic foci in a range of sites may be accompanied by vertigo. Epileptic vertigo must be distinguished from ‘vestibulogenic epilepsy’ a very controversial entity in which labyrinthine stimulation has been reported to precipitate an epileptic attack. There is little evidence to support this theory (Brandt 1999a). Notwithstanding the rare occurrence of epileptic vertigo in adults, the diagnosis of epilepsy in ‘funny turns’ and vertigo in children is more common and requires a high index of suspicion (Murphy and Dehkharghani 1994).

Cervical vertigo is defined as vertigo induced by changes of position of the neck in relation to the body, but there is much controversy as to the diagnosis and underlying pathophysiology of this entity (Brandt 1996b). Sympathetic irritation resulting in vertebrobasilar ischaemia, intermittent vertebral artery compression by osteophytes caused by cervical spondylosis, and deranged sensory input from the cervical kinesthetic receptors have all been postulated; there are no clear-cut clinical signs.

Good management relies upon accurate diagnosis. Neuro-otological assessment may enable the identification of a single pathology in many cases, but certain generalizations deserve mention:

A full general medical history, with specific reference to the cardiovascular and neurological systems should be obtained. In addition, the following neuro-otological history should be sought (Fig. 15.23).

Vertigo is a cardinal manifestation of a disordered vestibular system, whereas dizziness, light-headedness, faintness, or giddiness, are more common in general medical pathologies. Importantly, patients may report bizarre complaints, which tend to be dismissed by the non-expert, for example ‘my brain is sloshing around inside my skull’: ‘I feel like a goldfish in a bowl’, and ‘I feel that my brain is lagging behind my head’. Symptoms of depersonalization, difficulty concentrating, and impaired memory are all common with vestibular pathology. In addition, visual vertigo with nausea precipitated by strong visual stimuli, such as busy stations, supermarkets, escalators, patterned carpet, fast-moving television scenes, or scrolling computer screens, is common (Bronstein 2005) (Fig. 15.23).

Acute vertigo. Classically, vertigo of acute peripheral labyrinthine origin is unprecipitated, lasts less than a day, with rotational movement of the world, known as objective vertigo, or movement of the patient, subjective vertigo. Commonly there is accompanying nausea and vomiting, and more rarely diarrhoea. The patient becomes pale, sweats profusely, and is often acutely anxious.

Falls. In the case of falls, the history requires the evaluation of risk factors such as drug intake, neurological conditions, cognitive function, or general medical disorders. Environmental factors should be taken into account including an uneven or slippery surface, poor lighting, or an unfamiliar environment. Potentially treatable predisposing factors should be identified and corrected. A patient who suffers a single uncomplicated fall with no sequelae may be reassured and discharged, but recurrent falls with or without injury require careful assessment (Fig. 15.24) and a detailed evaluation of balance. For any particular fall there is a liability to fall, and an opportunity to fall factor. Both should be identified.

Instability A complaint of instability, unsteadiness or ‘weakness’ of the legs requires neurological investigation specifically to exclude cerebellar and brainstem disease associated with ataxia, proprioceptive loss, and neuropathy.

The time course should be defined for both the entire illness and the duration of individual episodes Firstly, it should be clarified whether the symptoms are constant or episodic, and if the latter, whether the episodes occur erratically or in clusters, with relapses and remissions.

‘Short episodes’ Attacks of acute rotational vertigo of less than one minute’s duration, which occur in clusters, are most commonly associated with benign paroxysmal positional vertigo (Section 15.3.1), which is particularly common after head injury and in the older age group. The periods of freedom from episodes may last many weeks or months. Particularly in the elderly, such brief episodes of dizziness may be misattributed to vertebrobasilar ischaemia, but in the absence of any concomitant neurological symptoms or signs, this diagnosis is unlikely.

‘Medium episodes’ Episodes of vertigo lasting several hours are common with migraine and Menière’s disease. The latter may usually be distinguished by fluctuating auditory symptoms and accompanying tinnitus, while in migraine a clear family history or past history of characteristic headache may facilitate diagnosis.

‘Long episodes’ Acute vertigo lasting more than 24 hours raises the possibility of an acute vestibular failure, due to a range of pathologies including vestibular neuritis, labyrinthitis, a vascular event, or trauma.

‘Chronic vertigo’ As noted above, following an acute vestibular event, symptomatic recovery occurs over a period of several weeks. Visual and somatosensory inputs and the cerebellum play a crucial role in recovery. The commonest cause of chronic vertigo is failure of compensation or intermittent decompensation after an acute labyrinthitis. The factors giving rise to failure of compensation (Fig. 15.8) should be specifically sought and excluded in patients presenting with chronic vertigo. More rarely, chronic persistent vertigo may result from central neurological disease such as multiple sclerosis, spinocerebellar degeneration, or vascular disease. Aassociated neurological symptoms or signs, particularly eye movement abnormalities, are the rule. Within the brainstem, vestibular symptoms are commonly associated with eye movement abnormalities, and other cranial nerve and long-tract symptoms and signs. It should be noted that bilateral vestibular failure may also present with chronic disequilibrium, associated with bobbing oscillopsia and reduction of visual acuity on movement.

Cochlear, general medical, and neurological symptoms occurring concurrently with the vestibular symptoms should also be sought. Pathology within the VIII nerve and labyrinth commonly involves both vestibular and auditory systems. However, in the elderly, who consider hearing loss as part of the ageing process, cochlear symptoms, including tinnitus, hearing loss and dysacusis remain unreported in association with vertigo unless specifically sought. A plethora of general medical disorders, including haematological, cardiovascular, and endocrine conditions may be associated with dizziness, and relevant systematic questioning should be undertaken.

Triggers for a patient’s symptom of disequilibrium should be identified. These vary depending upon underlying pathology. For example dizziness on standing from lying may suggest postural hypotension, while dizziness on tipping the head backwards may suggest benign positional vertigo. Oscillopsia and unsteadiness, particularly on uneven surfaces or in the dark, will suggest vestibular failure or a sensory ataxia due to loss of proprioceptive feedback.

The importance of a detailed drug history cannot be over-emphasized, as many drugs give rise to dizziness as a side effect (Table 15.6). The ototoxic effects of aminoglycoside antibiotics, and loop diuretics, should be borne in mind.

A full general medical examination with particular reference to the fundi, visual fields, visual acuity, and neurological and cardiovascular systems is essential. The specific clinical examination for vestibular and balance disorders includes:

A basic understanding of vestibular physiology and pathology is of key importance for a suitable neuro-otological examination.

Otological examination. In all patients with episodic vertigo, active chronic middle-ear disease with labyrinthine erosion must be excluded, and obvious otological abnormalities evaluated in the context of the clinical history and other signs. An abnormal appearance of the tympanic membrane requires an expert otological opinion. The presence of a perforation precludes caloric testing. A fluid level, cholesteatoma, or the bluish bulge of a glomus jugulare tumour should be noted. The presence of an auditory deficit as judged by tuning fork tests or whispered-voice test may suggest labyrinthine or VIII nerve pathology, but audiometry is the definitive test to exclude such disorders.

For the purposes of a vestibular examination, it is important to evaluate saccades, smooth pursuit, and optokinetic nystagmus (Section 13.2.1).

Saccades are rapid eye movements which may be assessed clinically by asking the patient to alternating fixate between targets at angle of 30° to right and left, and 30° up and down from the midposition of gaze, to assess horizontal and vertical saccades respectively. Delayed initiation, inaccuracy of fixation, or slow velocity of the saccades may all indicate neurological disease. These will impair the vestibular nystagmic response, as the fast phases of nystagmus are involuntary saccades.

Smooth pursuit is a slow eye movement which is intimately related to the mechanism of suppression of vestibular responses by optic fixation. It is assessed clinically by asking the patient to follow a target moving in the horizontal and then the vertical plane, and assessing ‘smoothness’of the eye movement. ‘Broken’ pursuit implies catch-up saccadic intrusions to enable the subject to maintain gaze on the moving target, if the smooth pursuit mechanism is deranged. Asymmetrically deranged pursuit almost always indicates neurological pathology, but symmetrically disordered pursuit may be pathological, for instance due to cerebellar or brainstem dysfunction. It may be associated with fatigue, old age, or psychotropic drugs including anticonvulsants, transquillisers, and antidepressants.

Optokinetic nystagmus is a reflex oscillation of the eyes in response to movement of the visual surround. For example, it may be seen in the eyes of train passengers who are watching objects passing outside the carriage window. The pathways subserving the optokinetic response include a cortical pathway, which is intimately related to smooth pursuit, and a subcortical pathway which passes through the vestibular nuclei (Fig. 15.25). Clinically, the response may be elicited by using a hand-held striped drum, or a piece of striped material such as school scarf or tie which is moved to the right and left, or up and down in front of the patient’s eyes, to examine horizontal and vertical optokinetic responses respectively. Asymmetry of horizontal or vertical nystagmus is sought. The importance of this test lies in the differentiation of peripheral from central vestibular pathology. In peripheral vestibular disease, the cortical pathway overrides, and no abnormality of optokinetic nystagmus is observed, except in the acute phase of a peripheral vestibular lesion, when spontaneous nystagmus may confound the optokinetic response. However, in neurological disease giving rise to disequilibrium, optokinetic abnormalities are seen in 60 to 75 per cent of patients, depending on the precise site of lesion (Table 15.7).

Detailed evaluation of spontaneous nystagmus is the key to defining the presence and location of vestibular pathology. Clinically, it is important to ensure that the eyes are conjugate and identify latent nystagmus, by performing a cover test, which may confound the interpretation of vestibular nystagmus. The presence of involuntary eye movements such as square-waves or saccadic flutter should be sought, and spontaneous nystagmus should be evaluated in the primary position of gaze, with eyes deviated to no more than 30°, to exclude the possibility of physiological endpoint nystagmus. Both horizontal and vertical nystagmus should be sought and observed, both with and without optic fixation using either Frenzel’s glasses or observing the eyes in a blackened room with an infra-red viewer.

Unilateral loss of afferent vestibular input gives rise to spontaneous nystagmus, which is directed, as defined by the direction of the fast phases, towards the normal ear. Irritative lesions may cause nystagmus with the quick component towards the disordered ear. Horizontal nystagmus of peripheral, labyrinthine, or VIII nerve origin obeys Alexander’s Law, which states that the nystagmus is always in one direction, irrespective of the direction of gaze, and that the intensity of the nystagmus is greatest when the eyes are deviated in the direction of the fast phase (Fig. 15.26). Nystagmus is described as:

In an acute vestibular lesion, one would expect to see third-degree nystagmus immediately after the onset of loss of vestibular function, but with the passage of time the nystagmus will gradually abate, such that it becomes second-degree and then first-degree, and finally is only observed in the absence of optic fixation. The following types of nystagmus arise from central neurological disorders, and imply the need for further neurological investigation (Table 15.8):

Under normal circumstances, the nystagmus generated by a peripheral labyrinthine stimulus, be it pathological or physiological, may be suppressed by visual fixation upon a target (Fig. 15.27). In attempting to differentiate peripheral from central unidirectional nystagmus, the effect of optic fixation is invaluable. In the absence of optic fixation, spontaneous nystagmus of peripheral type will be enhanced, whereas in the absence of optic fixation, spontaneous nystagmus of central origin will be attenuated, demonstrating a lower frequency and velocity (Fig. 15.28).

Positional nystagmus is an important sign, as it may be the only abnormality observed on clinical examination. Thus in every dizzy patient, a briskly performed Hallpike manoeuvre should be carried out (Fig. 15.11). The principle of the test should be explained to the patient, who should be told to observe the bridge of the examiner’s nose throughout the test. The head is turned 45° to the right or left, the side being determined by any suggestion of the patient as to which side is more likely to precipitate symptoms. The subject is then taken rapidly backwards with the head tipped over the edge of the bed at an angle of approximately 45°. The patient’s eyes are observed for the development of any nystagmic movement. If positional nystagmus develops, it is observed until it disappears, or for 2 or 3 minutes, after which it may be assumed that the nystagmus is persistent. The patient is then returned to the upright position, and the eyes are carefully observed for any reversal of a positional response. The procedure is then repeated with the head turned in the opposite direction.

In general terms, positional nystagmus may be divided into two main types, as outlined in Table 15.3, although their differentiation may prove difficult (Buttner et al. 1999). Nystagmus of peripheral type demonstrates a latent period of up to 30 seconds, followed by severe vertigo with rotatory nystagmus most commonly directed towards the undermost ear. During this period the patient may be distressed and feel acutely dizzy and nauseated. The symptoms and signs then gradually adapt, and if the patient is sat up, a reversal of the nystagmic response may be observed. If the procedure is then repeated in the same direction, the nystagmus frequently is less marked or absent, known as fatiguability. Care must be taken to carry out the procedure correctly on the first attempt, as it is possible that if the patient shuts their eyes and the examiner cannot observe the response, it will not be present on a second attempt.

The importance of the differentiation of positional nystagmus lies in the fact that transient positional nystagmus of the type described above is almost always of benign peripheral type, and easily treatable. By contrast positional nystagmus without a latent period, and which is vertical (Bertholon et al. 2002), or direction-changing, or which cannot be attributed to one of the forms of benign paroxysmal positional vertigo (Section 15.3.1) affecting each of the semicircular canals, is found to be of neurological origin in approximately 40 per cent of patients.

Vestibulospinal function cannot be assessed directly, and clinical examinations of balance are non-specific and insensitive in comparison with assessment of vestibulo-ocular function. Nonetheless, stance and gait assessments provide invaluable information with respect to a patient’s disability.

The Romberg test (1846) is performed by asking the patient to stand in the upright position with feet together, arms by the side, head straight forward and eyes closed. A tendency to sway to one side usually suggests peripheral vestibular pathology. An initial inability to stand with the feet together with the eyes open is more characteristic of cerebellar dysfunction. However, it must be emphasized that the Romberg test was initially developed to assess posterior column loss in tabes dorsalis, only becoming positive when the eyes are closed and depends upon a variety of sensory and motor systems. Thus, it is non-specific for vestibular disease. Patients with a psychological overlay to their vestibular disorders, often tend to fall promptly backwards like a wooden soldier on performing the Romberg test (Section 2.2.2).

The Unterberger test (Fig. 15.29) involves the patient marching up and down on the spot, with their arms closed and their hands clasped at an arm’s length in front of them. Normal subjects show little tendency to deviate to right or left, whereas patients with peripheral or central vestibular disorders tend to move linearly forwards or backwards, in addition to rotating to right and left. However, the value of the test in correlating findings with side and location of lesion is very limited.

Gait testing is assessed by asking a patient to walk towards a fixed point with eyes first open and then closed. In peripheral vestibular lesions there is a tendency to veer towards the side of the lesion, whereas in central neurological disorders and bilateral vestibular loss there is a tendency to walk on a wide-based gait. A variety of other gait disorders associated with balance dysfunction may be observed and provide valuable diagnostic information, for example, the slow shuffling parkinsonian gait, the high-stepping foot-dropping gait of posterior column loss or peripheral neuropathy and bizarre non-organic gait patterns that are frequently observed in patients with vestibular dysfunction, in whom a diagnosis has not been made and psychological overlay becomes prominent (Section 2.6).

The psychological correlates of vestibular disease deserve special consideration. In patients with persistent dizziness, psychiatric disorders have been demonstrated to be the second most common cause of symptoms, occurring in 10 to 25 per cent of patients (Jacob et al. 2003). Conversely, complaints of dizziness and feelings of loss of balance are extremely common in psychiatric patients, especially those with panic and other anxiety disorders such as agrophobia. Recent studies have demonstrated that the commonest psychiatric disorders associated with symptoms of disequilibrium are panic disorder, generalized anxiety disorder, phobic anxiety disorder, and depression (Furman and Jacob 2001). More specific syndromes such as space phobia (Marks 1981) and the motorist disorientation syndrome (Page and Gresty 1985) have been described in patients with both peripheral and central vestibular disorders. In a small percentage of patients, hyperventilation may compound the presentation of dizziness.

For the clinician evaluating a patient with disequilibrium, the common co-morbidity of psychological symptoms with vestibular disorders is important. In the past, patients have frequently been dismissed as simply being ‘stressed’ when their psychological symptoms have been precipitated by an underlying vestibular disorder (Eagger et al. 1992; Jacob et al. 2003). It is well recognized that vestibular compensation is rarely effective in the presence of psychological symptoms, and it therefore behoves the clinician to be aware of the relationship between psychological illness and vestibular disease (Fig. 15.30).

Self-rating questionnaires, such as the Hospital Anxiety and Depression Scale, the Beck Depression Inventory, the Fear Questionnaire, which detects phobic anxiety and avoidance behaviour, and the General Health Questionnaire, are of value in identifying psychiatric dysfunction as part of the overall clinical assessment. It is now well established that an effective treatment package for chronic disequilibrium addresses both the physical and psychiatric components of the disorder (Yardley and Luxon 1994).

Vestibular investigations define the presence and side of vestibular pathology and localize it to the peripheral, labyrinthine or VIII nerve, or central nervous system pathways. Classically, vestibular investigations have quantified the response of the horizontal semicircular canal to caloric, or thermal, stimulation and rotation testing, but the recent development of vestibular-evoked myogenic potentials also allows assessment of saccular function, while posturography provides information about the patient’s overall ability to balance and the strategy used for balance. None of the tests provides aetiological information regarding pathology.

The caloric test is widely regarded as the cornerstone of vestibular testing, and was first described by Barany in 1906. Fitzgerald and Hallpike (1942) popularized the technique using water 7°C below and above body temperature to irrigate the external canal for 40 seconds with the head raised 30° to the horizontal, to bring the horizontal semicircular canal into the vertical plane. The thermal gradient induced across the two limbs of the horizontal canal (Fig. 15.31) results in convection currents of the fluid within the canal, giving rise to displacement of the cupula, and stimulation of the crista. The nystagmic response generated is quantified, either by direct observation of its duration, or by electro-oculographic or videonystagmographic recording of the maximal slow-phase velocity.

Using this Fitzgerald Hallpike technique, the duration of the nystagmic response is observed with optic fixation. When the nystagmic response ceases, the room is totally darkened, and the eyes observed with an infra-red viewer, or Frenzel’s glasses are applied to the patient’s eyes to remove optic fixation, and the duration of the enhanced response in the absence of optic fixation is timed. Using the electro-oculographic or videonystagmographic response, the initial part of the caloric response is carried out in the absence of optic fixation, and at the peak of the response, the light is turned on to observe the effect of optic fixation.

Using either method, two main abnormalities are sought:

Two types of patterns are commonly observed. A canal paresis is one in which the responses generated by stimulation of the left ear are greater than the right ear, or vice versa. A directional preponderance is one in which the generation of nystagmus beating to the right is greater than the generation of nystagmus beating to the left, or vice versa. It should be recalled that irrigation of the ear with cool water generates nystagmus with beating of fast phases in the opposite direction, while irrigation of the ear with warm water generates nystagmus in the direction towards the irrigated ear. A mnemonic for recalling this pattern of results is COWS, Cold Opposite Warm the Same.

The degree of canal paresis and directional preponderance is calculated as a percentage by using the Jongkee’s formulae (1962):

Canal paresis percentage equals:

Directional preponderance (percentage):

where L = left, R = right; 30 and 44 represent water temperature and each integer, e.g. L30 and R44 represents the duration of nystagmus in seconds or the slow component velocity in degrees per second.

However, combined patterns can also be observed. For instance, in the case of a left labyrinthine lesion, a left canal paresis is associated with a right spontaneous nystagmus, and, therefore, a right directional preponderance. Hence the caloric result will give a left canal paresis, together with a right directional preponderance. This combined pattern will demonstrate a marked discrepancy between the hot responses, but little if any discrepancy between the cold responses. This pattern can easily be understood by summating algebraically the results that one would expect to find with a left canal paresis and a right directional preponderance (Fig. 15.34). However, central pathology, for example pathology in the left zone of the VIII nerve, may affect both the ipsilateral cerebellar vestibular connections and the left VIII nerve, giving rise to a left

canal paresis and a left directional preponderance. In this scenario, the cold responses will be widely disparate, whereas the hot responses will be very similar. These examples illustrate that for correct interpretation of the caloric test it is necessary to obtain all four irrigations, and that the widespread use of cold or hot irrigation as a means of obtaining rapid results will lead to an erroneous interpretation.

Bilaterally symmetrical increased or decreased caloric responses are difficult to detect, because of the wide range of normal values. A response of less than 90 seconds’ duration without optic fixation is generally considered to represent hypofunction. If no nystagmic response is observed with standard irrigation, irrigation at 20°C for 1 minute is usually undertaken to determine whether or not there is any significant residual function.

In addition to the pattern abnormality, the ability to suppress vestibular nystagmus with optic fixation provides information as to whether there is impaired integration of visual and vestibular responses at the level of the vestibular nuclei or cerebellum.

An index greater than 1 indicates normality or a peripheral vestibular disorder, with normal optic fixation suppression of the vestibular response. Values equal to or less than 1 indicate central nervous system pathology.

The patterns of abnormal results on caloric testing may, in general terms, be interpreted as follows:

The caloric test is simple, widely available, and provides information about the severity and location of vestibular dysfunction, based on horizontal semicircular canal function. Moreover, in a very simple format, it allows each ear to be assessed independently. The disadvantages of the caloric test are that it is not well tolerated by some patients and it is difficult to interpret in the presence of middle ear disease, for example it cannot be undertaken in the presence of a perforation and with a middle ear effusion, the transmission of the thermal gradient is uncertain. Perhaps most importantly, the caloric test with unilateral stimulation of the labyrinth is unphysiological, particularly in comparison with rotational testing.

Rotational tests (Fig. 15.35) enable stimulation of both peripheral labyrinths by the application of multiple graded accelerations. This contrasts with the caloric test which stimulates each labyrinth in turn. Moreover, rotational testing is a physiological stimulus, enabling correlation of the stimulus to the semicircular canal response.

For all practical purposes, current rotation tests assess the function of the horizontal semicircular canals, although by altering the axis of rotation it is possible to stimulate the horizontal or the vertical canals, with or without otolith stimulation in addition (Table 15.9). The relationship between the stimulus and response can be described by three calculated parameters:

Thus, within this range of stimulation, vestibular-induced eye movements are compensatory, that is they are virtually instantaneous and precisely match head movement. This range of 0.5 to 5 Hz matches the predominant frequencies of rotational head movements during walking and running, (Grossman et al. 1988). Thus ideally, vestibulo-ocular reflex measurements would include testing across a similar stimulus range, but the construction of a rotational chair (Fig. 15.35) is such that the usual frequency range of stimulation varies between 0.01 to 1 Hz, with a maximum velocity of 50 to 60° per second. The majority of patients, both children and adults, tolerate the test well, and valuable data can be obtained.

The most common test paradigms are sinusoidal harmonic acceleration and a velocity step. Sinusoidal harmonic acceleration comprises a succession of rotations at different frequencies, with the disadvantages being long test duration and resultant difficulty in maintaining patient alertness. The velocity step paradigm consists of a rapid acceleration from a velocity of 0 to 60° in less than 1 second with recording of the nystagmus response until cessation, followed by an abrupt stop. This provides a more physiologically relevant high-frequency stimulus and is a less time-consuming test. However, during rotational tests, alertness is vital, and the patient should be asked to perform mental arithmetic. Moreover, if the gain of the response is low because of vestibular hypofunction, measures of symmetry and phase are likely to be inaccurate.

Active head-only rotational testing has been introduced as an inexpensive and transportable piece of equipment (Fig. 15.36) (O’Leary and Davis 1990). Eye movements are recorded by standard electro-oculography (Section 15.5.3), and a head accelerometer measures head movement. An auditory cue from a metronome allows the patient to keep time to generate head movements of variable frequencies and velocities from 0.1 to 6 Hz. Both horizontal and vertical movements can be recorded, although electro-oculography is an unsatisfactory technique for the measurement of eye movement recordings. A computer program analyses the head and eye movement responses to generate gain and phase measurements. A major advantage is that auto-rotation testing provides a measurement of gain of the vestibulo-ocular reflex above 1 Hz, which lies in the normal physiological range, but its disadvantage is that patients often find it quite difficult to undertake the task. Also, at rapid head movements, it is difficult to stabilize the accelerometer on the headband, with resultant poor test/retest reliability of gain measurements.

Eye movement recording allows documentation and analysis of oculomotor responses to visual and vestibular stimuli. A number of techniques are available with advantages and disadvantages depending on the requirements of the clinician (Table 15.10)

Electronystagmography also called electro-oculography is the mainstay of clinical eye movement recording. A potential difference exists between the retina and the cornea, with the retina being negative with respect to the cornea. In the normal situation of conjugate eye movements, electrodes are placed at either outer canthus, and as the eyes rotate towards the right, the right electrode becomes positive with respect to the left, and vice versa. Deviation of the eyes in the horizontal plane causes a potential difference between the two active electrodes, and a ground electrode is placed on the forehead. The magnitude of the potential difference is proportional to the magnitude of the eye movement. This voltage difference activates a pen recording system and provides a trace of the eye movement. Conventionally, an upward movement of the pen represents deviation to the right, and a downward movement deviation to the left (Fig. 15.37).

Electro-oculography is a good technique for horizontal eye movement recording, but lid artefact impairs adequate vertical recording. The technique is relatively inexpensive, widely available, and provides an accurate quantified measurement of eye movement recordings, both spontaneous and in response to visual and vestibular stimuli. The major disadvantages of the technique are the need for scrupulous skin cleansing and careful application of the electrodes, with low electrode skin impedance; the confounding effect of eyelid artefact and muscular activity near the electrodes, produced for example by blinks, and the variability of the corneo-retinal potential with respect to ambient light. Thus repeated calibrations throughout eye movement recordings are essential.

Video-oculography is a video recording of eye movements using a small video camera that is placed in front of the eyes on a specific device. It is rapidly becoming a widely available clinical tool, and is reliable for both horizontal and vertical eye movement recording. The movement of the eye is determined by image processing, using either two-dimensional or three-dimensional systems. Most systems function in total darkness using infra-red light, and the majority of commercial systems use a standard frame-rate of 50 to 60 Hz, limiting the use of video-oculography for recording saccades. The technique avoids the confounding factors of changes in room lighting, myogenic activity, and repeated calibration, but is in general less well tolerated by the patient than electronystagmography.

Scleral search coil is the most accurate form of eye movement recording and is now considered ‘the gold standard’. However, it is an invasive technique that requires a wired contact lens to be placed on the patient’s eyes. It causes discomfort and is not routinely employed for clinical purposes.

Galvanic stimulation refers to the delivery of a small electric current through the vestibular labyrinth using surface electrodes and recording either eye movements or postural movements (Fig. 15.38). The technique has been recognized for more than 100 years, but has not gained clinical acceptance, initially because of the painful electric currents required to produce recordable results, and more recently because it is unclear exactly which vestibular end-organ is responsible for the eye movement or postural response. The advantages of the technique are that galvanic stimulation tests each labyrinth separately, and is thought to excite the synapse between the hair cell and the VIII nerve afferent. It was therefore considered a possible tool to evaluate ‘neural’ versus ‘sensory’ function and could, in theory, be used to evaluate unilateral VIII nerve disorders. More recent work has suggested that this may prove to become a valuable clinical tool.

Strong acoustic stimulation may lead to short-latency muscle contractions, known as vestibular-evoked myogenic potentials, which may be recorded from the tensed sternocleidomastoid muscle using a surface electrode (Fig. 15.39). The pathway for this response is considered to arise in the saccule, and passes along the inferior vestibular nerve to the lateral vestibular nucleus and from there via the vestibulospinal reflex to the sternocleidomastoid muscle (Murofushi et al. 1995; Zhou and Cox 2004).

The value of this test is that it provides a simple technique for evaluating otolith as opposed to semicircular canal function, and moreover can be undertaken in patients in whom the vestibulo-ocular reflex cannot be studied accurately, for example, uncooperative children, subjects who are blind or who have congenital nystagmus, or have other eye movement disorders. Moreover, it allows evaluation of the inferior as opposed to the more commonly studied superior vestibular nerve. There are two uncertainties of the technique:

To date, no single recording technique has been agreed, although many studies have reported abnormalities of vestibular-evoked myogenic potentials in unilateral VIII nerve and labyrinthine disorders (Welgampola and Colebatch 2005; Osei-Lah et al. in press).

The Subjective Visual Vertical and Subjective Visual Horizontal tests evaluate otolith function, with influence from the semicircular canals (Pavlou et al. 2003) Such perceptual tasks of orientation with respect to gravity provide an alternative means of evaluating vestibular function in patients in whom it is not possible to assess the vestibulo-ocular reflex. Using simple instruments, a normal subject can align a laser beam in relation to the earth horizontal and vertical in a totally darkened room, without visual cues, in a very reproducible manner (Friedmann 1970, 1971). Following an acute peripheral vestibular disorder, deviation towards the affected side is commonly observed. However, with compensation, the subjective visual vertical and horizontal tests frequently return to within the normal range. Central vestibular disorders produce abnormal subjective visual vertical and horizontal test results consistently with caudal brainstem lesions causing ipsiversive tilts of the subjective visual vertical, whereas upper brainstem lesions cause contraversive tilts. Recent work has suggested that standardization of the test technique may result in better diagnostic accuracy in peripheral vestibular disorders (Pagarkar et al.  in press).

Assessment of vestibulospinal function in isolation is difficult because of the interaction of sensory and motor systems in maintaining balance. Static-force platforms measure the position of the centre of gravity, and allow measurement of body sway. However, the major limiting factors of such devices relate to the combination of systems used in maintaining stability and upright stance, and the absence of any stimulus response measures, with respect to vestibulospinal function. Thus, static-force platforms merely record spontaneous body movements, and while this may be of value in clarifying a dysfunction in an individual, it is rarely of value in defining vestibular pathology.

Moving platform, or dynamic, posturography (Fig. 15.40) was devised to overcome these limitations, by:

Dynamic posturography relies upon coupling of the platform to the sway of the subject, and by maintaining the angle between the foot and the lower leg at a constant value, the input of the somatosensory system to postural control is reduced. The system also allows visual information to be ‘sway-referenced’ to the subject, so that visual input can be reduced by movement of the visual surround in the same direction as any body sway, thus providing inappropriate visual information to the subject. These posturographic techniques have been valuable in defining the contribution of the different sensorimotor components to postural control. The Report of the Therapeutics and Technology Assessment Committee of the American Academy of Neurology (1993), highlights that posturography is not a diagnostic test, but a method to quantify balance dysfunction under different sensory conditions. Thus, this technique has advanced the knowledge of how postural mechanisms work, and how posture is impaired in patient groups, but adds little to the diagnosis of an individual patient complaining of a balance disorder (Bronstein 2003).

Successful management of patients with vestibular dysfunction depends upon accurate diagnosis, an understanding of vestibular physiology, the physician’s awareness of the overlap between the vestibular system and the autonomic and limbic systems, and the psychological manifestations that frequently accompany vestibular disorders. Evaluation of progress and efficacy of intervention require careful monitoring, not least as vestibular signs and test results do not correlate with symptoms. Consequently, it is of value to use validated questionnaires documenting vestibular symptomatology, disability, and handicap, for example the Dizziness Handicap Inventory (Jacobson and Newman 1990) or the Vertigo Symptom Scale (Yardley and Putnam 1992), in addition to validated psychological questionnaires such as the Beck Anxiety and Depression Scale and the Short Form 36. Objectively, posturography results may provide clear guidance as to suitable physical therapy intervention in terms of balancing strategies and may provide objective quantification of functional improvement.

Treatment may be classified under five main categories:

Based on the diagnosis, a rehabilitation plan should be devised for each patient, and specific care should be taken to ensure understanding of the vestibular condition to ensure compliance with the rehabilitation programme (Table 15.11).

A general medical examination will identify comorbid systemic conditions such as hypertension, vascular disease, diabetes, autoimmune disorders, ophthalmological disease, and psychological pathology, all of which may impact upon vestibular compensation and require appropriate treatment. In particular, ophthalmological and rheumatological or orthopaedic problems should be addressed, to ensure optimal visual and somatosensory input to enable vestibular rehabilitation.

Pharmacological intervention for vestibular disease is chosen for one of three reasons:

Recent research has led to a better understanding of the neurochemistry of the vestibular system and thus a more rational basis for the treatment of vestibular pathology. Nonetheless, there has been no development of new drugs and the treatment of vestibular disorders remains empirical in the absence of well designed drug trials (Bamiou and Luxon in press).

Symptoms of vertigo, nausea, vomiting, sweating, pallor, and diarrhoea are extremely alarming for the patient, who commonly fears a brain tumour or stroke, and simple reassurance is effective for the majority of patients. The nature of the symptoms should be explained and anti-emetics should be administered, for example hyoscine, prochlorperazine, promethazine, cyclizine, dimenhydrinate or metaclopramide. Buccal administration of prochlorperazine is frequently effective, but intramuscular treatment can be used, if oral preparations cannot be tolerated because of vomiting. Hyoscine may be administered transdermally. Anti-emetic drugs block the afferent pathways from the chemoreceptor zone in the area postrema, the gastrointestinal tract, and the labyrinth (Timmerman 1994; Takeda et al. 1993) to the medullary vomiting centre.

Vestibular sedative drugs should then be administered and include the anticholinergics hyoscine and scopolamine, the antihistamines promethazine, prochlorperazine, cyclizine, metoclopramide, and dimenhydrinate, and the calcium channel antagonists, cinnarazine and flunarizine. The latter two drugs may give rise to extrapyramidal side effects, and should be used only for a very limited period in the elderly (Daniel and Mauro 1995).

Diazepam has no specific action on the vestibular system, but acts by reducing neural activity and causing inhibition throughout the central nervous system, including the vestibular nerve and nuclei (Smith and Darlington 1998). While the role of this drug in the treatment of vertigo is controversial, it is widely used for its anxiolytic activity in acute vestibular crises (Foster and Baloh 1996). There is some recent evidence to hypothesize efficacy for steroid treatment in promoting recovery of labyrinthine function in the initial phase after an acute vestibular episode (Straube 2005).

Menière’s disease. The treatment of Menière’s disease remains controversial and empirical, not least because the underlying pathophysiological mechanism of this disorder defies definition. A very high placebo response has been reported (Claes and van de Heyning 1997), and there are a few double-blind randomized trials assessing treatment efficacy. The aim of pharmacological intervention is the control of endolymphatic hydrops or treatment of the postulated immunological mechanisms responsible for endolymphatic hydrops. Failure of medical intervention may lead to surgery, including chemical labyrinthectomy with transtympanic installation of gentamicin or surgical destruction of the labyrinth or vestibular neurectomy.

Treatments aimed at influencing endolymphatic hydrops include diet, diuretics (Santos et al. 1993), and the use of betahistine, a histamine analogue reported to improve circulation in the stria vascularis (Lacour and Sterckers 2001). No double-blind trials have reported the efficacy of a low-salt diet, 1 to 2 mg/day, but the author’s experience is that this is a highly effective strategy in patients who can be persuaded to follow the regime strictly. Patient compliance depends upon education regarding the high levels of salt in many prepared foods, such as cornflakes.

There is evidence that diuretics are effective in the long-term control of vertigo, but not of hearing impairment, although there is no good randomized double blind trial (Thirlwall and Kundu 2006). More potent loop diuretics such as frusemide should be avoided, due to potential ototoxicity. Bendroflumethazide, diazide (Van Deelen and Huizing 1986), a potassium-conserving diuretic, and chlorthalidone (Klockhoff et al. 1974) are all reportedly effective. Despite a number of trials using betahistine, none have demonstrated convincing efficacy (James and Burton 2001).

Treatments aimed at immunological suppression (Hamman and Arnold 1999) are based on the assumed autoimmune pathogenesis of Menière’s disease (Silverstein et al. 1998). Steroids have been administered topically and systemically (Parnes et al. 1999), but no double-blind studies have demonstrated clinical efficacy. Various alternative treatment regimes have been suggested in this condition including alternobaric oxygen therapy (Fattori et al. 2002) and intermittent micropressure pulses to the inner ear through a tympanostomy tube with the Meniett device (Densert and Sass 2001). A prospective randomised placebo controlled, multicentre trial of this device reported good results (Odkvist et al. 2000).

Not infrequently, in non-specialist units, Menière’s disease is treated by straightforward symptomatic management with vestibular sedative drugs and anti-emetics. Failure of treatment leads to the consideration of destructive procedures, and intratympanic gentamicin treatment is currently the preferred option (Silverstein et al. 2003). It has been reported that there is a high efficacy in controlling vertigo with this management strategy (Bottril et al. 2003). There is no agreed optimal protocol regarding the dose, technique, and administration or end-point of therapy, and profound sensorineural hearing loss may develop in up to 30 per cent of treated cases (Blakley 2000). Moreover, recurrence of vertigo has been reported in up to 30 per cent of treated cases within 24 months of treatment (Wu and Minor 2003).

Surgical interventions (Ludman 2003) may also include theoretical prophylactic measures such as endolymphatic sac decompression, but there is no firm evidence of the efficacy of this procedure (Thomsen et al. 1996). Destructive surgical procedures may be divided into those that aim to preserve auditory function, such as vestibular neurectomy, and those aimed at removing the labyrinth if the disease process has caused profound hearing loss, in addition to the intractable vertigo. In the latter situation, labyrinthectomy is commonly advocated, if medical treatment has failed. However, destructive procedures should be undertaken with extreme caution in view of the possible bilateral loss of auditory and vestibular function in Menière’s disease, and the possible failure of compensation for a total unilateral vestibular loss.

Migraine. Migraine affects approximately one-fifth of the population. Although the association between migraine and vestibular signs and symptoms is well described, it is poorly understood (Eggers 2006). The treatment of migrainous vertigo parallels the treatment of migrainous headache (Bikhazi et al. 1997). This includes dietary measures, life-style adaptation, and stress reduction techniques, together with psychological treatment and vestibular exercises in the 25 to 30 per cent of patients with migrainous vertigo who demonstrate peripheral vestibular dysfunction.

In the absence of clear diagnostic criteria for migrainous vertigo and limited randomized controlled trials, clinical experience suggests that pharmacological treatment of migrainous vertigo may result in resolution or improvement of acute vertiginous episodes in over 90 per cent of those treated cases (Johnson 1998). Pharmacological treatment includes both symptomatic and prophylactic measures. Symptomatic treatment may include both anti-vertiginous and anti-emetic drugs, together with specific treatment for headache; for example aspirin, paracetamol, ibubrufen, or non-steroidal anti-inflammatory analgesics (Baloh 1997). Triptans (Neuhauser et al. 2003), ergot drugs, and acetazolamide may all also be of value as acute treatments (Bamiou and Luxon in press).

Prophylactic treatment can be considered for frequent acute episodes of vertigo or episodes of sufficient severity that symptomatic treatment is inadequate (Baloh 1997). Betablockers such as propranolol; calcium channel blockers such as cinnarizine, and serotonin reuptake inhibitors such as pizotifen, in addition to tricyclic antidepressants, such as amitriptyline have all been effective in some cases (Bamiou and Luxon in press).

Episodic ataxia type 2 may present with acute vertigo and ataxia, with or without interval symptoms in both adults and children. Although rare by comparison with migraine, this diagnosis should be considered in intractable recurrent vertiginous episodes. Acetazolamide or 4-aminopyridine may be effective in the management of episodic ataxia type 2 (Strupp and Brandt 2006), while a case with a novel mutation in the CACNA1A gene, also recorded a good therapeutic response to acetazolamide coupled with valproic acid.

Central vertigo giving rise to chronic vestibular imbalance and dizziness is the most difficult condition to treat. It is often associated with disordered eye movements including central forms of nystagmus: vertical, period alternating, see-saw, and pendulum nystagmus. No single treatment is of benefit to all patients, but current understanding of the neurochemistry of the central vestibular system has enabled a rational approach to specific treatments for some of these disorders (Rucker 2005). Frequently, treatment of the eye movement disorder may lessen the sense of disorientation and associated nausea. Baclofen has been effective in treating periodic alternating nystagmus (Halmagyi et al. 1980) while acetazolamide, a drug which stabilizes the transient dysfunction of abnormal calcium channels is an effective treatment for episodic familial ataxia type II (Baloh 2002). Downbeat nystagmus may respond to clonazepam (Young and Huang 2001) whilst 3,4-D-diaminopyridine, a potassium channel blocker has also been suggested in the treatment of this condition (Strupp et al. 2003). Gabapentin (Averbuch-Heller et al. 1997) and memantine, a glutamate antagonist with NMDA blocking action (Starck et al. 1997), have both been reported to be effective in the treatment of acquired pendular nystagmus due to multiple sclerosis. There are no specific treatment regimes and frequently these drugs are used on a therapeutic trial basis, titrating the dose against symptoms and side effects. For patients with chronic instability due to central vestibular disorders there is now some evidence to suggest that intensive vestibular rehabilitation physiotherapy and gait retraining strategies may be effective in providing greater confidence and reducing disability (Shepard et al. 1993).

The majority of patients with chronic vertigo suffer from uncompensated peripheral vestibular pathology. Progressive or persistent vestibular pathology, for example due to acoustic neurinoma, migraine, or autoimmune inner ear disease, may present with chronic vertiginous symptoms. Absence of vestibular function and central vestibular disorders may present similarly. Uncompensated unilateral peripheral vestibular dysfunction and bilaterally reduced or absent vestibular function with chronic symptoms should be managed in a similar manner. Patients with fluctuating pathology, such as Menière’s disease, benign paroxysmal positional vertigo, or migraine require management of acute episodes prior to standard vestibular rehabilitation (Black et al. 2000). Anti-emetics or vestibular sedative drugs should not be used in the management of this group, as they may impair vestibular compensation (Zee 1988). Unfortunately such drugs are commonly prescribed for chronic vertigo, both in primary and tertiary care.

Plasticity of the central nervous system underpins vestibular rehabilitation and symptomatic vestibular compensation. During the Second World War, Sir Terence Cawthorne, an otolaryngologist, and Dr Harold Cooksey, a rheumatologist, noticed that servicemen with head injuries and dizziness recovered more quickly, if they were active. The Cawthorne–Cooksey exercises were subsequently developed on an empirical basis. The programme comprised a systematic graduated set of exercises aimed at stimulating vision, vestibular, and proprioceptive inputs to enhance recovery. In the 1970s and 1980s, animal models of vestibular compensation demonstrated the value of vision and motor activity (Igarashi et al. 1975, 1981; Lacour 1976; Lacour et al. 1979; Lacour and Xerri 1980) in symptomatic recovery from unilateral vestibular disorders. This contributed to the evidence-base underpinning the current approach to vestibular rehabilitation. Vestibular compensation relies on a range of physiological mechanisms involving adaptation and habituation, resulting in recalibration of the vestibular reflexes, and sensory and motor substitutions, including for example greater reliance on visual inputs for balance, as well as ‘new’ predictive oculomotor responses. A range of vestibular rehabilitation programmes have been devised (Norre and De Weerdt 1980; Shepard and Telian 1995; Herdman and Whitney 2000) to promote compensation. All contain key elements: