39 Writer's and craft cramps

Ancient Chinese writings contain reference to the prevalence of hand cramps amongst brush writers [quoted by Bindman and Tibbetts (1977)]. The first medical description of writer's cramp, however, is thought to be that of Bell (1830) and this was further elaborated the following year by Bruck. The disorder was attributed to the advent of the steel nib, which was gradually replacing the quill pen (Fig. 39.1). In 1864 Solley published a paper entitled ‘Clinical Lectures on Scriveners’ Palsy or the Paralysis of Writers’ in which he emphasized that ‘the greatest part of the middle classes in London got their bread by the use of the pen, either as the exponent of their own thought or the thoughts of others, or in the recording of the sums gained, lost, or spent in this great emporium of commerce – this vast Babylon’. Writer's cramp, Scriveners’ palsy, Schreibkrampf, or ‘la crampe des ecrivains’ seemed particularly common in Victorian times and this may have been due to the huge army of clerks who spent most of their day writing by hand in this pre-typewriter era (Fig. 39.2). Poore (1872, 1878, 1897) provided clinical details of well over 100 patients and claimed to have seen more than 500 examples of the disorder during his professional life. Duchenne (1883) drew attention to not only writer's cramp but also similar symptoms in other occupational groups, including pianists, cobblers, tailors, florists, fencers, turners, and tinmen. Gowers (1888) described these disorders as ‘occupation neuroses’, but in keeping with the 19th century use of the term ‘neurosis’ he implied a physical illness without discernable cause, rather than the present-day implication of a psychological disorder. In fact he voiced his opinion that writing and other occupational cramps were physical disorders and that writer's cramp was due to abnormal function of a ‘writing centre’, possibly in the cerebral cortex. This concept of an organically based brain disorder as the cause of such symptoms was popular around the turn of the century (Osler 1892, Jelliffe 1910). Collier and Adie (1922) believed musculoskeletal and peripheral nerve abnormalities were not the cause and stated ‘the malady is certainly of central origin and the combination of pain, spasm and loss of control points to the region of the basal ganglia as the site of the breakdown in function which produces the disability’. Babinski (1921) noted an association between writer's cramp and spasmodic torticollis and this was confirmed by Barre (1925, 1952), who also noticed a relationship with local disease of the neck, cervical myelopathy, apical pleural lesions, and encephalitis. From the 1920s onwards it became increasingly popular to view these cramps in terms of the expanding psychoanalytic theories. Thus Janet (1925) thought they were due to faulty learning experience resulting in bad habits. Other authors stressed the psychoneurotic aspect and associated writer's cramp with obsessive-compulsive behaviour, stuttering, hysteria, depression, and maladjusted personality (Culpin 1931, Pai 1947, Fergusson 1971, Sarkari et al. 1976). Crisp and Moldofsky (1965) stressed that early in childhood the arms are involved with grasping and clinging while later are important in rejecting objects. They pointed out how the upper limbs are involved in emotional states and become major organs ‘of the expression of anger at the non verbal musculo-skeletal level’. They viewed the cramp as being due to inner emotional tensions and felt that patients with writer's cramp showed a tendency to suppress or deny emotion, being ‘tense, strong, sensitive, conscientious, precise, emotionally overcontrolled people’. Then the pendulum has swung the other way and scientific psychological evaluation in larger numbers of patients has failed to reveal any abnormality compared with control groups (Sheehy and Marsden 1982). Evidence has been marshalled to suggest this group of disorders is organic, arises from a central cause, and is a variety of focal dystonia.

Writer's cramp is a disorder characterized by involuntary and excessive contraction of the muscles of the upper limb (especially those of the hand and forearm) on attempting to write. This results in impaired writing and abnormal posturing of the hand, forearm, or upper arm. In simple writer's cramp these features are present in isolation, whereas in dystonic writer's cramp dystonic posturing of the limb occurs at other times, particularly when using it to perform manual tasks. Sometimes simple writer's cramp develops into dystonic writer's cramp and this transition has been called progressive writer's cramp (Sheehy and Marsden 1982). Writer's cramp may occur as part of generalized dystonia and may either proceed or follow other dystonic features. It may just spread to involve the neck or opposite upper limb and thus become a segmental dystonia. The former is more likely with childhood onset, whereas the latter is more frequent with adult onset. Writer's cramp occurring as part of generalized dystonia is not considered further in this chapter.

Craft or occupational cramps may be defined identically to the above except that a function other than writing is impaired. In all of these the hand is used for repetitive, stereotyped movements, frequently at a rapid rate. Moldofsky (1971) and Hunter (1978) have drawn up extensive lists of occupational cramps and at least 55 have been described (Table 39.1). Activities involving rapid

finger or wrist movements, such as playing the piano and other musical instruments, typing, and telegraph operating, figure prominently. These disorders have sometimes been called occupational or craft palsies, but as true weakness may not be present, they are best referred to as cramps.

Not all discomfort, pain, stiffness, tightness, or cramp, which occur when performing such tasks, are due to true writer's or craft cramps. Many arise from local musculo-skeletal or peripheral nerve problems and these need to be distinguished. Thus, interview with and examination of all members of seven orchestras revealed 64% with painful overuse syndromes (Fry 1986). Prevalence ranged from about 74% among string players to 32% among percussionists. In a survey of hand difficulties experienced by professional musicians, 42% were found to be due to inflammatory and 9% to non-inflammatory disorders of tendons and joints. Another 15% were due to peripheral nerve and nerve root entrapment, while 27% were thought to arise from disorders of motor control (Table 39.2) (Hochberg et al. 1983). It is amongst this latter group that the occupational cramps, which are the subject of this chapter, are to be found, and in a large study Hochberg et al. (1988) found 14% of 100 musician-patients had focal occupational dystonias. Biomechanical factors in the hand, such as limitation of passive or active abduction of the digits, have been reported to be common in such musicians, and by interfering with high speed digital movements may lead to programming abnormal patterns of activity (Wilson et al. 1993). A variety of disorders may masquerade as writer's or craft cramp, including entrapment of peripheral nerves and nerve roots (Komar and Szegvari 1983, Murphy 1989, Mafulli and Mafulli 1991), spinal muscular atrophy, multiple sclerosis, and Parkinson's disease, in addition to generalized dystonias which start in the hand (Sheehy et al. 1988). In most such other causes local inflammation, swelling, pain, muscle wasting, and weakness are the major features and the inappropriate, excessive muscle contraction, which is the hallmark of writer's and occupational cramps, is absent (Fry 1988). Co-contraction in agonists or antagonists in the forearm in association with cervical nerve root and cord lesions, however, has been noted to slow rapid hand movements (Satoyoshi et al. 1972). Many cases reported in the literature as writer's, occupation, or craft cramps have not been adequately screened for such alternative causes.

There are no known biochemical changes in the brain, cerebrospinal fluid, or blood accompanying writer's and other occupational cramps, but adequate studies have not been performed.

The exact central nervous system neurophysiological changes accompanying writer's and occupational cramps are not fully understood. Some information available comes from electromyography (EMG). During writer's cramp there is increased activity in muscles normally involved in writing, especially wrist and finger extensors and brachioradialis but also finger flexors, trapezeus, deltoid, and triceps. In addition there is activation of muscles seldom used in writing, such as biceps. These changes are present from the start of writing. Similar excessive contraction may be present when performing other tasks, especially if these involve rapid fine movements, even though there is no clinical dystonia at these times (Hughes and McLellan 1985). Similar findings are reported

in other occupational cramps, with excessive and prolonged EMG bursts, which may occur simultaneously in agonists and antagonists (Cohen and Hallett 1988). Some patients show greater activity in these muscles when the limb is at rest than normal subjects (von Reis 1954). Lundervold (1951) observed similar findings in patients with other occupational cramps and noted a spread of activity to the contralateral non-working arm.

Using the technique of paired stimuli to radial and median nerves, (Chapter 35, ‘Generalized Primary Dystonia’), Sheehy et al. (1988) reported decreased inhibition of the H-reflex which is maximal 10–40 msec after the first stimulus (Fig. 39.3). This phase of inhibition is thought to be due to the action of Ia interneurons. Similar findings suggesting decreased inhibition at spinal interneurons in writer's and musician's cramp have been reported by subsequent workers (Nakashima et al. 1989, Panizza et al. 1989) Such disinhibition or facilitation of reflex activity is similar to that noted in generalized primary dystonia, cranial dystonia, and spasmodic torticollis (see Chapters 35, 37 and 39), but a late potentiation seen at 200 msec reported in spasmodic torticollis and generalized dystonia does not occur (Panizza et al. 1990).

For transcranial magnetic stimulation see later.

The pathophysiological mechanism underlying writer's and occupational cramps is entirely speculative. Peripheral factors have been stressed by several authors (Charlin 1954, Komar and Szegvari 1983), but as mentioned above such patients can usually be readily distinguished and form a separate group. Spinal cord mechanisms have also been suggested but lack convincing support (Barre 1925, 1952). An abnormality of brain function, originally proposed by earlier workers (Gowers 1888, Osler 1892, Jelliffe 1910, Collier and Adie 1922), has been supported by subsequent studies (Marsden 1976, Sheehy and Marsden 1982). It has been proposed that these cramps are a form of focal dystonia, similar to spasmodic torticollis and cranial dystonias. This is largely based on 1) the occurrence of identical disability in generalized idiopathic torsion dystonia, 2) the association of these disorders with segmental dystonia, such as occurs with concurrent spasmodic torticollis, 3) the presence of frankly dystonic movements and postures when performing other acts such as is seen in dystonic writer's cramp, and 4) the association with other neurological signs of central origin such as tremor (see later under ‘Clinical features’). The argument that these other forms of dystonia are due to central mechanisms, and in particular to abnormal extrapyramidal function, causing disinhibition or facilitation of interneurons involved in reflex arcs, is covered in those sections. With the preliminary results presented above in the ‘Neurophysiology’ section, it seems as though this may apply to writer's cramp as well. Support for this notion has been advanced by Tempel and Perlmutter (1990) who found that the increase in blood flow in the primary sensorimotor cortex demonstrated by positron emission tomography (PET) scan following vibration to the hand was reduced in subjects with idiopathic dystonia compared with controls. They interpreted this as possibly resulting from decreased excitatory transmission in the sensorimotor cortex, either as a primary abnormality or secondary to abnormal function in the ‘basal ganglia-thalamo-cortical circuit’. Seven of their 11 patients had writer's cramp.

Ceballos-Baumann et al. (1997) using activation PET studies in patients with writer's cramp on repeated writing of a stereotyped word found activation of the striatum and its frontal lobe association projection areas (including premotor and dorsal prefrontal cortex) paralleled with underactivation of motor executive areas (supplementary motor areas, SMA) and primary sensorimotor cortex in patients compared with normal controls. Ibanez et al. (1999) also reported similar results. Interestingly, treatment with botulinum toxin did not improve the underactivation of the motor cortex, suggesting this was a direct consequence of dystonia and not a secondary effect of muscular co-contraction (Ceballos-Baumann et al. 1997).

Hallett (2006) who reviewed the literature summarized imaging techniques concluded that virtually all neuroimaging studies of various types showed activation of the contralateral primary motor cortex, the contralateral primary sensory cortex, the premotor cortex, the supplementary motor area bilaterally, and the cerebellum ipsilaterally.

An abnormal negative-slope component of the Bereitschaftpotential has been demonstrated in patients with writer's cramp performing a voluntary hand contraction or relaxation (Deuschl et al. 1995). Because this component is generated in the primary and supplementary motor areas, its abnormality seems to confirm the above PET finding of impaired activation of the executive motor areas. Paradoxically, Siebner et al. (1999) found that low frequency repetitive transcortical magnetic stimulation (rTMS) (which has an inhibitory effect) of the motor cortex produced improvement in writing ability in eight of the 16 patients studied, lasting up to 3 hours. It is questionable whether inhibiting the already inhibited (or hypoactive) motor cortex can be beneficial in dystonia and it is possible that the observed effect was due to the spread of magnetic pulses (and concomitant inhibition) of the premotor cortex which is thought to be overactive in dystonia.

Other recent studies have suggested abnormally reduced cortico-cortical inhibition in the pathophysiology of writer's cramp (e.g. Ridding et al. 1995). Similarly, Filipovic et al. (1997) reported a task-specific shortening of the post-excitatory silent period during writing compared with isometric contraction in patients with writer's cramp using transcranial magnetic stimulation (TMS)-evoked motor responses. The post-excitatory silent period is a well-established marker for intracortical inhibition.

There also seems to be growing evidence that focal dystonia may be caused by alteration in central processing or a plasticity change of the motor system in response to disordered sensory inputs (Grunwald et al. 1997) or disordered sensorimotor integration (Odergren et al. 1996). In one study using hand vibration, dystonia was easily provoked by tonic vibration reflex and this effect was markedly attenuated by the blockade of muscle spindle afferents (Kaji et al. 1995). This has led some to suggest that dystonia is a ‘sensory’ rather than a motor disorder (Hallet 1996). Support for this has come from animal experiments in primates whereby frequent simultaneous sensory stimulation led to difficulty using the hand, which was reminiscent of action dystonia (Byl et al. 1996). Based on this notion, some authors have investigated the effect of repetitive transcortical magnetic stimulation (rTMS) applied over the sensory cortices (Schneider et al. 2010)

Whether there is an interaction between environmental and genetic (or other) factors which predisposes certain individuals to develop such focal dystonia remains unclear and will doubtless be the focus of further investigations.

Although cases of hysterical difficulty with performing specific tasks may exist, attempts to explain writer's and other occupational cramps on a psychological basis are unsatisfactory and do not stand up to recent critical analysis (see earlier under ‘Historical background’). Harrington et al. (1988) found little evidence of generalized anxiety or anxiety specific to the writing situation and there was no significant difference between patients and controls on the Crown-Crisp Experimental Index, which contains several anxiety subscales. Similarly, extraversion and neuroticism, as assessed by the Eysenck Personality Inventory, show no abnormality (Hughes and McLellan 1985) and psychiatric symptoms seem uncommon in musicians experiencing painless hand cramps (Newmark and Hochberg 1987).

There is no known racial predilection to writer's or occupational cramp. The prevalence in the general community is uncertain but has been assessed at 69 per million persons in a Mayo Clinic study (Nutt et al. 1988). Writer's cramp formed 5.1% of all primary dystonias and was the next most common focal dystonia following craniocervical dystonia and spasmodic dysphonia in an epidemiological study from North England (Duffey et al. 1998). Sarkari et al. (1976) estimated it was 5.4 per 1000 in office workers. Hand cramp was reported in 14% of telegraphers, and in over half of these cases it was said to affect writing as well (Ferguson 1971). This extremely high incidence of writer's cramp (being in excess of 7%) suggests that either excessive work load involved in telegraphy [i.e. a Morse key operator may make twice as many muscular contractions per minute as a typist (Ferguson 1971)] predisposes to writer's cramp or difficulty with writing in this group results from muscular fatigue or other factors and is not true writer's cramp. Excessive work load, speed, and effort have been suggested to predispose to writer's cramp (Gowers 1888) and periods of abstention from writing to improve it (Sheehy and Marsden 1982). It seems likely, however, that another mechanism underlies difficulty with writing in some cases of this fatigued group. Occupations involving writing, however, figure prominently in surveys of patients and only five out of Sheehy and Marsden's (1982) 34 patients had jobs that did not depend on writing or typing. Excessive strain caused by repetitive movements has been thought to possibly underlie some cases of dystonic hand cramps seen in musicians. Hochberg et al. (1988) found that 14% of 1000 musician-patients had these spasms. In 17 of 57 such patients, increase in practice time occurred just before the onset of the cramp (Newmark and Hochberg 1987) and such a relationship has also been noted by others (Wilson et al. 1993). Unlike the telegraphers, however, almost all of these cases had simple and non-progressive musician's cramp, although the combination of writer's and musician's cramp may occur (Sheehy et al. 1988). Periods of rest from playing do not seem to help the dystonic variety of musician's cramp (Newmark and Hochberg 1987), suggesting that even if ‘muscular strain’ plays a part in its genesis, once it has developed it becomes autonomous of such influences.

Occasional cases have a family history of writer's cramp (Martinez-Martin and Bermejo-Pareja 1985) and this occurred in 5.5% of Sheehy et al.'s (1988) patients, in which parent and child were both affected. In a study of idiopathic focal dystonias in which relatives of affected individuals were examined, two out of 10 cases of writer's cramp had a parent with the same condition (Waddy et al. 1991). These and others concluded that most cases of isolated writer's cramp in Britain, along with the related idiopathic focal dystonias of the neck and cranial muscles, might result from the presence of an autosomal dominant gene or genes with reduced penetrance. (Schmidt et al. 2009) One woman in the study of Sheehy et al. (1988) with simple writer's cramp had a daughter in whom writer's cramp progressed to generalized primary dystonia, suggesting that in some cases this focal dystonia may be only a fragment of the latter condition. In keeping with this notion, in series of patients with generalized or segmental focal dystonia there have been obligate carriers of the genetic abnormality amongst the relatives in whom the clinical expression has been that of writer's cramp (Marsden and Sheehy 1990). A German family was reported with the DYT1 gene mutation in whom four of the five affected individuals presented as dystonic writer's cramp during late childhood or adolescence (Gasser et al. 1998). The condition sequentially affected both sides but did not progress to a generalized form of dystonia. The authors concluded that rarely early onset familial writer's cramp may be a manifestation of DYT1 dystonia. Similarly, there have been reports of DYT6 dystonia manifesting with arm dystonia. It should be noted, however, that this is a rare family and that sporadic adult onset cases do not have mutations in the DYT1 or DYT6 gene.

Simple writer's cramp affects both sexes equally (Sheehy et al. 1988), but progressive and dystonic writer's cramp and musician's cramp have been recorded about twice as often in men as in women (Newmark and Hochberg 1987, Sheehy et al. 1988, Soland et al. 1996). To a large extent the frequency of occupational cramps must be dictated by the sex distribution within the occupation. It is thus not surprising that typist's cramp seems more frequent in females (Table 39.3) (Sheehy et al. 1988).

Writer's cramp usually commences between 20 and 50 years of age, with a mean of 38 years, but occasional cases may even start in the first decade of life (Sheehy et al. 1988). Approximately 10% of patients report the onset followed severe psychological stress or trauma to the involved limb or elsewhere. In 5.5% of Sheehy et al.'s (1988) cases, the interval between local trauma and cramp was short (under 3 months). The mechanism underlying such a relationship remains uncertain. The possibility that stress is unmasking a latent disability cannot be excluded (Gowers 1888, Sheehy and Marsden 1982). The onset is usually gradual, although occasionally it may be abrupt. In approximately a quarter of cases the disorder is initially intermittent and occurs on only some occasions or after prolonged writing. In virtually all cases, however, it progresses and becomes continuous so that the disability is present on every attempt to write. If initially intermittent it may be made worse with emotional stress (Sheehy and Marsden 1982). Approximately three quarters of patients commence as simple writer's cramp but a quarter show progression so that roughly equal numbers end up with simple and dystonic writer's camp (Sheehy and Marsden 1982, Sheehy et al. 1988). In the majority, progression occurs within the first 6 months, but it may be delayed for up to 30 years. Occasionally the reverse occurs and dystonic writer's cramp will convert to the simple variety.

The incidence of left handedness seems the same as in the general population. Writer's cramp develops in the dominant extremity and it thus affects the right hand much more frequently than the left. In occupational activities, however, which involve both hands equally, such as typing, the left hand is affected as often as the right (Sheehy and Marsden 1982).

About one third of patients with writer's cramp take to writing with the opposite hand (Fig. 39.4), but a quarter of these develop simple or dystonic writer's cramp in that extremity (Sheehy et al. 1988). Approximately half of sufferers can still write at least a few words with the affected hand.

Although these disorders are termed ‘cramps’ they do not always present as such and there may be a variety of initial complaints. Thus many patients describe decreased speed, clumsiness, difficulty in moving the hand, freezing, tremor, or sudden jerking. There may be a sensation of stiffness and tightness in the hand or forearm. Pain is present in approximately 15% of cases (Marsden 1983).

Examination often shows difficulty in picking up or holding a pen and dystonic posturing of the hand may occur (Table 39.4). As writing commences, the pen is usually held with excessive force and there is often marked flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint of the index finger. The pen may be held in the hand in an abnormal way, sometimes in an attempt to compensate for the writing difficulty. The abnormality usually increases as writing continues with exaggeration of grip, flexing of the wrist, pronation of the forearm, and gradual lifting of the wrist, forearm, and elbow from the table. As writing progresses, the pen frequently shifts in the hand so that the normal acute angle formed between pen and paper increases to 90 degrees and may even reverse, becoming obtuse (Fig. 39.5). Rarely the digits may lift from the pen and hyper-extend. Often writing is reasonably normal for the first few words or lines, but it then becomes increasingly difficult to move the hand across the page and it may become stuck in the one spot. Occasionally the hand becomes tremulous or gives a sudden jerk. The writing becomes progressively cramped and illegible. In other patients this sequence may not occur and both the act of writing and legibility are severely impaired from the outset.

When the activity involves repetitive flexion and extension of digits, such as when typing or playing a musical instrument, there may be a decrease in speed, stiffness, and aching and a tendency for some of the digits on the affected hand to curl up or ‘claw’. Newmark and Hochberg (1987) defined three patterns of disturbance in 59 instrumental musicians who presented with painless uncoordinated movements (see Table 39.5) The first occurred in 22 pianists and involved involuntary flexion of the fourth, fifth, and occasionally third digits (Fig. 39.6). In 20 cases it was the right hand that was involved. The authors noted this hand was at a mechanical disadvantage compared with the left one.

The second pattern was noted in five guitarist or banjo players and consisted of difficulty with extension of the third digit, with occasional involvement of second and fourth digits as well. Thus, after plucking a string, extension was slowed, making it difficult to rapidly repeat this movement, as required in tremulo.

The third picture occurred in five clarinettists who had involuntary flexion of the fourth and fifth digits, especially affecting scales with trills. There was associated extension of the third digit, which was felt to be compensatory.

In 37 of the 59 musicians there was a history of inflammation (‘tendinitis’ or ‘tendosynovitis’), trauma, or increased demands on the hand preceding the onset of symptoms. Two patients developed their symptoms following resolution of an acute peripheral neuropathy.

All musicians experienced technical difficulties in playing, especially affecting speed and volume. In none was there spread of difficulty beyond the hand, although a few experienced problems with other activities, such as typing or writing.

Similar findings in musicians have been found by others (Sheehy et al. 1988) and it has been noted that violin players may develop involuntary flexion of the fourth and fifth digits, with loss of performance as they press down on the finger board.

Overall, the small finger seems to give musicians with occupational cramp a disproportionate amount of difficulty. This may be because of inherent mechanical disadvantages, but it has been proposed that there is an innate atavistic tendency to ignore this digit and it has been noted that its inclusion in playing musical instruments is a relatively late historical development (O’Donovan 1992).

As mentioned above, patients with dystonic writer's cramp or other dystonic occupational cramps develop dystonic movements of the affected limb when performing unrelated actions. Thus there may be dystonic posturing when using a knife or fork, holding a cup or saucer, doing up buttons, tying shoelaces, using a zipper, putting a key in a lock, sewing, knitting, using a variety of tools, and so on. Approximately half of Sheehy et al.'s (1988) patients

with writer's cramp ended up with these additional dystonic movements. Musician's and other craft cramps seem less liable to produce such additional movements, reasons for which are quite unclear.

Simple or dystonic writer's and occupational cramps may remain confined to the upper limbs and Sheehy and Marsden's (1982) patients had the disorder for between 4 and 38 years (mean of 15 years) without involvement at other sites. This series, however, specifically excluded patients with dystonia elsewhere and thus did not encompass all cases in which such upper limb cramps occur. The association of writer's cramp with spasmodic torticollis is well recognized (Babinski 1921, Barre 1925, 1952, Meares 1971) and approximately 45% of segmental dystonias involving either the arm and neck or arm and trunk commence with writer's or occupational cramp (Sheehy and Marsden 1982). Writer's cramp, however, may occur at some stage during the course of the disease in as many as 77% of patients (Marsden 1983). Adult onset cases are much less likely to spread and Marsden (1976) found that even in dystonic writer's cramp less than a half spread to be segmental and none developed into generalized dystonia.

Some patients present with the problem of tremor on writing. There are three varieties: 1) essential tremor, 2) primary writing tremor, and 3) writer's cramp with tremor. Essential tremor and primary writing tremor are discussed under ‘Essential Tremor’ (Chapter 17). With respect to essential tremor, there is also debate as to whether tremor in these patients should be classified as essential or dystonic.

The association of tremor and writer's cramp is well recognized (Gowers 1888, Poore 1897, Jelliffe 1910, Pai 1947). Tremor is present in approximately one third of patients with writer's cramp and may occur in simple or dystonic varieties or other occupational cramps (Sheehy and Marsden 1982, Sheehy et al. 1988). Occasionally it will be severe, even in the simple variety of these cramps. It may be made worse by writing and this is sometimes the major cause of disability.

There seem to be two main groups of patients who develop tremor with writing, but these merge one into the other (Table 39.6 and Fig. 39.7). Absolute distinction between these disorders may be impossible, and in some cases artificial, as individual patients occasionally show clear features of both conditions. Nonetheless, it is usually possible to categorize patients with tremor affecting writing as having either benign essential tremor or writer's cramp with superadded tremor. Patients with the former condition may have 5–7 Hz postural tremor seen with the arm outstretched or if the limb is held in an unusual position, such as with a finger almost touching their nose. A small group of patients develop similar 5–7 Hz tremor on writing and probably also have benign essential tremor. Such patients may grip the pen tightly or hold the hand in an abnormal way to try to control the tremor. Only by asking them to relax and write with their hand naturally may it become apparent that there is no dystonia. Conversely, patients with true writer's cramp not only are unable to relax their grip on the pen as they write, but also develop dystonic posturing of the hand, which often becomes exaggerated if they are asked to write in their original way. Tremor in writer's cramp may be asymmetrical and greater in the arm with cramp. Occasionally it may even be more marked in the contralateral arm.

As well as other disorders, which may present or masquerade as writer's cramp, there may occasionally be additional subtle neurological signs. Impaired arm swinging when walking has been reported in approximately a quarter and increased tone in 10%.

These have been in the limb affected by cramp and have been present in both the simple and dystonic varieties (Sheehy and Marsden 1982). About 7–9% of cases have carpal tunnel syndrome, but this seems to be secondary to the strain caused by the writer's cramp (Newmark and Hochberg 1987, Sheehy et al. 1988).

Sheehy and Marsden (1982) found that approximately a fifth of patients with writer's cramp gave up writing and another fifth

changed to using the opposite hand. The remaining patients continued to write with the affected limb with varying degrees of disability. Many of them develop special tricks, such as holding the pen in a peculiar way, using the opposite hand to steady and help propel the affected one, or using a particular type of pen, such as one with a wide diameter or a broad felt tip. Less than 5% of patients changed their occupation as a result of writer's cramp. Patients with simple writer's cramp tended to be less disabled than those with the dystonic type. A variety of other movements were affected in dystonic writer's cramp, but these patients retained independence in dressing, feeding, toileting, and so on (Sheehy and Marsden 1982). Although, as outlined above, expanded numbers have altered these proportions slightly, the general trend is the same and at follow-up after 6 years the original patients showed virtually no change. In particular none had progressed to develop dystonia elsewhere and none had experienced sustained remission (Sheehy et al. 1988).

Routine haematology, biochemistry, and radiology are normal. Bilateral caudate calcification, visible on CT brain scan, has been reported, but as this is a fairly common finding in otherwise normal subjects, it seems unlikely to be relevant (Sheehy and Marsden 1982). True calicification is discussed under ‘Fahr's disease’. The neurophysiological and PET scan findings have been mentioned above under ‘Neurophysiology’ and ‘Pathophysiological mechanisms’. In young onset (below age 26) familial cases it may be reasonable to do the DYT1 and DYT6 gene test as this may be the rare first manifestation of the condition, as mentioned earlier (Gasser et al. 1998).

Although many different treatments have been attempted in writer's cramp (Fig. 39.8), there has not been a thorough evaluation of drug therapy. A range of drug types have been tried, including anticholinergics, benzodiazepines, dopamine receptor blocking drugs, dopamine store depleting drugs, l-dopa, amantadine, baclofen, tricyclic antidepressants, and anticonvulsants such as phenytoin, carbamazepine, and sodium valproate (Sheehy and Marsden 1982). Occasionally success is reported in individual patients, but overall results are poor. Oral anticholinergic drugs are perhaps the most useful (Sheehy and Marsden 1982), but uncontrolled evaluation should be regarded with some scepticism as double blind intravenous administration is ineffective (Lang et al. 1983). Propranolol may be helpful in those patients in whom tremor adds to the disability (Sheehy and Marsden 1982), but when tremor is the predominant feature, there may be response to anticholinergics rather than beta-blockers (Kaihi et al. 1985, Ravits et al. 1985). Because the disorder causes limited disability and most drugs produce symptomatic side effects, the majority of patients prefer to manage without medication.

Thalamotomy and deep brain stimulation have been reported successful in single cases with writer's cramp accompanied by tremor (Seigfried et al. 1969, Fukaya et al. 2007). Because disability caused by the disorder is limited, such treatment, with its attendant risks, is seldom justified.

Writer's and craft cramps may be treated by botulinum A injections. The general principles underlying the use of this toxin have been discussed above under ‘Cranial Dystonias’ and ‘Spasmodic Torticollis’ (Chapters 37 and 38). Clinical examination and EMG are used to define the precise muscle bellies that are overactive and the toxin is injected into the target muscles under EMG monitoring. It is usually satisfactory to inject into the midpoint of a muscle belly, rather than search for the motor end point. Using this technique and injecting the most active muscles in increasing doses every 2 weeks until performance improvement was obtained, Cohen et al. (1989) achieved functional improvement in 16 out of 19 patients with writer's cramp. Hand writing became more legible and ability to play musical instruments or to type was improved (Fig. 39.9). Clinical improvement, however, did not occur without some weakness and treatment only lessened EMG activity, without altering basic disturbances in the patterns of muscle activation. Improvement lasted from 1–6 months and was repeated on reinjection (Cohen et al. 1989). Subsequent studies, however, have not shown such good results and useful relief of symptoms has frequently necessitated troublesome hand weakness. In a further report from this group of workers (Karp et al. 1994) 53 patients were treated for up to 6 years. Although 81% of patients had improved after at least one of the injection sessions, 65% of those who were followed for at least 2 years discontinued treatment. Sixty-five per cent of injections had produced transient weakness and the mean interval between injections was 6 months.

Rivest et al. (1990) injected 12 patients without EMG guidance and found seven patients achieved significant benefit while five were complicated by disabling weakness. In a subsequent report from this same group using EMG guidance, 44 patients were treated for a mean period of 12 months. Significant writing improvement followed 56% of treatment sessions but mild weakness occurred after 32%. Sixty-five per cent discontinued treatment, usually after the initial injection, but 36% obtained sustained functional improvement. By contrast, a double blind placebo-controlled cross-over study showed improvement in writing in only 20% of patients, although 60% were said to have better pen control (Tsui et al. 1993). In these patients, however, a standardized dose of botulinim toxin was used per muscle, unlike long-term studies which have generally tailored the dose to suit individual patients.

Relaxation and retraining were advocated by earlier writers for the treatment of writer's cramp (Poore 1872, 1897, Gowers 1888). Emphasis on keeping the muscles of the hand and forearm as relaxed as possible and performing the movements of writing with the proximal limb musculature was advocated as ‘the smaller the muscles employed (to move the pen) – the more readily does cramp occur’(Sheehy and Marsden 1982). These techniques continue to be used and form the basis of avoidance conditioning (Beech 1960, Sylvester and Liversedge 1960) and biofeedback therapy (Bindman and Tibbetts 1977).

Psychotherapy (Crisp and Moldofsky 1965) and hypnosis (Besson and Walker 1983) have been reported to improve a few patients, but no large-scale study has been undertaken and most cases lack follow-up data. Wieck et al. (1987) undertook a controlled study of habit reversal training in nine subjects and compared them with 11 controls. There was some improvement for up to 3 months but it was no greater than that seen with relaxation training. Mechanical aids designed to increase or alter the grip on the pen have been said to help a few patients (Koller and Vetere-Overfield 1989, Lees et al. 1989). Such devices have been tried since the early 20th century (Quinn 1989).

In summary, treatment of writer's and other occupational cramps is not fully satisfactory. Relaxation, biofeedback techniques, and transcutaneous electrical stimulation (TENS) (Tinazzi et al. 2005) may be worthy of trial, but the degree of benefit is often not great and may not be sustained. Botulinum toxin injections may be helpful but require expertise and precision and the degree of weakness necessary to produce relief may prove unacceptable. The vast majority of patients do not have a psychiatric basis and psychotherapy is ineffective and inappropriate. Because of the limited degree of disability, most patients prefer to put up with their symptoms, rather than to embark on long trials of unsatisfactory drug therapy.