13.3 An overview of cerebral palsy

Cerebral palsy is a descriptive umbrella term describing a permanent disorder of movement or posture due to non-progressive lesions of the immature brain. It is the most common childhood movement disorder with an incidence of around 1:400 live births (2–2.5/1000 live births). Despite improvements in obstetric and perinatal care, the incidence has not changed significantly over recent decades.

Although the cerebral lesion is itself static, the clinical manifestations typically evolve over time and with growth. For example, the abnormal movements of dyskinetic cerebral palsy are rarely seen in infancy and the full clinical picture is often only established by the second year. Children with a moderate diplegia often deteriorate during adolescence and become non-ambulant.

Cerebral palsy is defined as a motor disorder but there are often associated conditions, such as perceptual and sensory changes, disturbances of feeding and communication, cognitive and behavioural difficulties, and seizures. This has led to recent calls for a more inclusive definition that acknowledges the wider functional effects of cerebral palsy.

Over recent years a better understanding of the causes of cerebral palsy has been reached due largely to detailed epidemiological studies that have included neuroimaging. Magnetic resonance imaging (MRI) is the more sensitive tool. It allows assessment of the aetiology and timing of the cerebral insult and can provide important prognostic information for families, not just for the affected child but also for future pregnancies. A recent review identified abnormal neuroimaging in 80–90% of children with cerebral palsy. Scan abnormalities may be summarized into three main types as follows.

Malformations most commonly result from disruption in normal neuronal migration during early pregnancy (<20 weeks’ gestation). They account for around 10% of imaging abnormalities seen in children with cerebral palsy. Whilst the majority of these defects are sporadic, there are a number of recognized genetic, infective, and metabolic causes that should be excluded. Typically neuronal migration disorders result in the abnormal development of the gyral and sulcal patterns as in lissencephaly (Figure 13.3.1), pachygyria, and polymicrogyria, or in the periventricular heterotopic collection of abnormal neurones. Occasionally, an early destructive process impedes migration resulting in parenchymal clefts or cysts lined with heterotopic grey matter and often associated with cortical dysplasia (e.g. schizencephaly (Figure 13.3.2) and porencephaly). Infants are usually born at term with no obvious risk factors. The clinical features vary from mild hemiplegia to severe quadriplegia. Epilepsy is particularly common in these conditions.

White matter abnormalities represent damage occurring before 34 weeks’ gestation. They are most common in premature infants. The classical pattern is one of a loss of periventricular white matter (PVL, periventricular leucomalacia, Figure 13.3.3) associated with signal change on T₁- and T₂-weighted images. Changes generally affect the posterior ventricular regions in diplegia and are more extensive in quadriplegia. Characteristically there is associated irregular enlargement of the lateral ventricles and thinning of the corpus callosum. If the damage is more extensive, both cortical and subcortical changes may result (multicystic encephalomalacia) and a more severe clinical picture is seen.

Damage confined to grey matter is uncommon but is seen in children with dystonic cerebral palsy.

Focal infarcts may also extend into grey and white matter. They are almost exclusively seen in children with hemiplegia, involving middle cerebral artery territory.

Hydrocephalus is not uncommon in cerebral palsy, particularly following intraventricular haemorrhage related to prematurity. This is distinct from secondary ventriculomegaly due to the volume loss of cerebral atrophy.

The causes of cerebral palsy are often multifactorial. It was once considered that the majority of cases were due to birth trauma but in term infants with cerebral palsy, the current consensus is that less than 10% are due to birth asphyxia itself. Infants that are already compromised in utero are likely to be more vulnerable during the delivery itself. As discussed later, different causal factors are implicated in the different forms of cerebral palsy.

Risk factors are generally divided into prenatal, perinatal (from labour to the end of the first week of life), and postnatal factors. In most term infants, the origins of cerebral palsy can be traced back to the prenatal period, whilst in preterm infants, damage usually occurs perinatally (Table 13.3.1).

Cerebral palsy risk increases with decreasing gestation and birthweight. Studies consistently show that prematurity (<37 completed weeks’ gestation) is the single most important risk factor for cerebral palsy; the risk being approximately eight times higher than in term infants. With intrauterine growth retardation (IUGR) where birthweight is significantly less than that expected for the gestational age, the risk of cerebral palsy is increased further. Although improvements in neonatal intensive care have increased the survival rate of extreme preterm infants, the risk of significant complications remains high, particularly in those of very low birthweight (≤1500g). Around 15% of infants of very low birthweight will suffer severe intraventricular haemorrhage or PVL, the majority of whom will go on to develop cerebral palsy. Other major complications such as chronic lung and bowel disease (bronchopulmonary dysplasia and necrotizing enterocolitis) are common in this group. Overall, these children account for only 2.2% of all live births, but they comprise almost 40% of the cases of children diagnosed with cerebral palsy each year in the United States of America.

A multiple pregnancy increases the risk of premature delivery, intrapartum complications, and low birthweight. In itself it is an independent risk for cerebral palsy, particularly where there is fetal or infant death of a twin and this is probably due to monochorionic placentation resulting in twin-to-twin transfusion.

Postnatal factors are generally defined as events occurring outside the neonatal period (>28 days postdelivery) and distinguish acquired from congenital cerebral palsy. There is poor agreement as to the upper age limit for this definition which in different studies varies from 2–10 years. Postnatal causes account for 10% of cases of cerebral palsy and despite an improved understanding of the underlying causes in this group, the incidence has not changed significantly recently. The causes in order of frequency are listed in Table 13.3.1. The acquired injuries most commonly result in hemiplegic or four-limb cerebral palsy. An acquired diplegia is very rare.

Cerebral palsy syndromes are generally classified by the clinical nature of the motor disorder, namely the tonal abnormalities and the anatomical distribution of these abnormalities. There have been many attempts to refine this traditional classification that fails to consider underlying pathological or aetiological factors and any of the associated impairments. The clinical groups are themselves ill-defined: the distinction between asymmetric diplegia and hemiplegia, and between diplegia and quadriplegia is often inconsistent. By convention the predominant tonal abnormality is reported, but in reality, tone is often mixed with both pyramidal and extrapyramidal components.

Surprisingly, there is no measure of function within the current classification system but increasingly physicians are adding some measure of functional grading to the clinical description of cerebral palsy. The Gross Motor Function Classification System (GMFCS) is the most widely used validated measure that can be used as a basis for prognostic counselling and planning management. It is based on longitudinal observations and provides a description of the pattern of gross motor development by severity and age (Figure 13.3.4).

For the practising clinician, the traditional definitions (as described by Hagberg and Hagberg, 1993) still apply and are described here.

The spastic motor disorders are the most common and seen in 60–70% of children with cerebral palsy. Spasticity is just one feature of a wider ‘upper motorneuron syndrome’ and these other factors should also be considered when managing a child with spasticity. They comprise both positive and negative features as illustrated in Table 13.3.2.

This is the most common cerebral palsy syndrome accounting for around 33% of cases. Clinically, it is characterized by increased muscle tone with legs more affected than arms. Walking is often delayed but more than 50% of affected children will eventually walk. It is the most common consequence of preterm delivery; around 70% of children with diplegia having been born before 36 weeks gestation. The classical pathology of diplegia relates to the PVL seen in preterm infants. This damage typically affects motor fibres to the lower limbs. The nearby optic radiations are also vulnerable accounting for the visual difficulties and strabismus often seen in diplegia. Other associated conditions include epilepsy in around 15% of children and mild to moderate learning difficulties in 30%.

It is seen in less than 10% of children with cerebral palsy but these children are likely to have multiple difficulties and significant functional impairment. Damage may result from a variety of cortical and subcortical lesions particularly multicystic encephalomalacia but also from severe PVL and brain malformations. Tone is increased in both upper and lower limbs and often involves bulbar musculature so that typically these children show extensive feeding and communication difficulties. Only the minority will walk. Over 80% will have microcephaly and significant learning difficulties. Epilepsy is present in more than 50%.

Manifest as a unilateral paresis with spasticity, hemiplegia is the second most common cerebral palsy syndrome. It is seen in around 25% of children with cerebral palsy. It is often congenital and without any clear prenatal event. Focal ischaemic lesions and subcortical periventricular lesions are the most common causes. Unilateral brain malformations may be seen in term infants. Congenital hemiplegia often has an apparent ‘silent period’ with the absence of clinical signs in the first 4–5 months. The appearance of strong hand preference around this time may be the first sign of an abnormality. Fifty percent of children with hemiplegia will walk at the appropriate time and most are ambulant by age 2 years. Comorbid features are common, particularly undergrowth of the affected side with abnormal sensation. Visual problems in terms of hemianopia should be looked for. Epilepsy, which is strongly associated with learning difficulties, is present in 30% of cases and subtle behavioural problems are common.

The abnormal movements or postures result from defective coordination and/or regulation of muscle tone. The group is subdivided into dystonic and hyperkinetic forms. In dystonic cerebral palsy (10% of cases), there are slow sustained tonic contractions of limbs or axial musculature, which are often provoked by emotion and effort and associated with persisting primitive reflexes, particularly the asymmetric tonic neck reflex. In hyperkinetic cerebral palsy (5% of cases) movements are purposeless and involuntary and may comprise athetoid movements that are slow, writhing, and distal, or jerky, more proximal choreic movements. There is often some associated spasticity. In the older child, the repeated, uncontrolled neck flexion and extension may lead to a secondary spinal cord myelopathy.

Typically, the child with dyskinetic cerebral palsy is initially hypotonic before the classical features emerge by the second year of life. Dyskinetic cerebral palsy is seen in both term and preterm infants. In the term infant it is most often the result of acute severe peripartum hypoxia. In the preterm infant, it is associated with more prolonged severe hypoxia and/or hyperbilirubinaemia, where neonatal jaundice has led to kernicterus, defined as dyskinetic cerebral palsy associated with sensorineural deafness, abnormal dentition, and supranuclear ophthalmoplegia. Neuroimaging commonly shows basal ganglia changes, sometimes in conjunction with more widespread cortical damage.

This is the least common subgroup (<10%) of cerebral palsy. The predominant clinical features are those of a non-progressive cerebellar ataxia with poor balance and coordination and intention tremor. The diagnosis is made with caution as there are a number of very slowly progressive disorders, such as Pelizeus–Merzbacher disease that can mimic this clinically. Neuroimaging should always be performed.

From the history, a child may already be identified as ‘high risk’ for cerebral palsy, namely through antenatal detection or through perinatal events and such children should be assessed regularly and early intervention offered if/when physical signs emerge. In many children the diagnosis of cerebral palsy is not suspected initially but even in these cases a careful history may reveal risk factors, not previously recognized and on assessment ‘warning signs’ of neurological abnormality may be detected (Box 13.3.2). The child who is labelled with cerebral palsy is presumed to have a static motor disorder. However, motor abnormalities may be the earliest signs of a neurodegenerative disorder (genetic or metabolic disease) or they may be an early manifestation of more global developmental delay. The clinician should always consider an alternative diagnosis if the child with ‘cerebral palsy’ has a strong family history of motor disorder, or if history and investigation fail to provide an underlying explanation. Suspicions should also be raised if the physical signs themselves are unusual, such as clearly progressive or fluctuating in nature.

To establish the diagnosis of cerebral palsy, further investigation should be considered: neuroimaging is now widely available and is generally advised. It enables clarification of aetiology and more accurate discussion of the likely neurodevelopmental outcome. Neuroimaging will show characteristic abnormalities in approximately 85% of children with cerebral palsy. Many of the neurodegenerative conditions have distinct and characteristic scan abnormalities. Further genetic, metabolic, and neurophysiological tests are indicated if the diagnosis of cerebral palsy is not established or if an alternative diagnosis is suspected.

There are some rare conditions where diagnosis is best established by a ‘trial of treatment’. This is particularly true when despite investigation, cerebral palsy remains unexplained and is associated with a dystonia. There is a spectrum of dystonias which are partially or fully responsive to dopamine. The best described, Segawa syndrome, is often diagnosed initially as a spastic/dystonic diplegia. Children classically present with an abnormal gait that worsens through the day and is improved by sleep. Diagnosis is confirmed by genetic testing and measurement of cerebrospinal fluid (CSF) neurotransmitters. The presentation of the dopa-responsive dystonias is highly variable so that where there is uncertainty, paediatric neurologists advocate a 3–6 month trial of high dose L-dopa.

In 2001, the World Health Organization revised their classifications of impairment, disability, and handicap suggesting that classification should now be based on functioning and disability from the perspectives of the individual (structure and function) and society (activities and participation). The principal aim of management is to maximize a child’s potential both as an individual and within society. This requires a holistic approach that is responsive to the specific difficulties of each child and his/her family. For children in the United Kingdom with cerebral palsy, care is generally delivered through a multidisciplinary Child Development Team often coordinated by a key worker (Figure 13.3.5).

In the child with cerebral palsy, mobility and posture will be of particular concern but other associated conditions should always be considered and indeed there may be times when they are functionally more significant then the motor difficulties themselves. These may include aspects of feeding and communication and medical issues, such as epilepsy, the management of hydrocephalus, and visual problems. Support around behaviour, social care, and education is also essential and often, in more severely involved children, a large team of professionals is involved.

With respect to management, problems and priorities should be agreed between the child, parents, and therapists. Any intervention undertaken should have a clear aim and where possible the outcome measured objectively. In terms of physical management the aims are to maximize function and prevent the complications that result from abnormal tone. Physiotherapy is the first line of intervention and may be delivered through many different techniques. To date, no one method has proven superior. Physiotherapy generally includes muscle stretching and strengthening, to encourage the maintenance of active and passive ranges of joint movements and, where necessary, positioning and seating are addressed. Orthotics are often used to support this.

Systemic or focal medications may be indicated if abnormal tone is clearly affecting function and/or delivery of care. The means of administration and any potential side effects should be carefully considered. The goals of treatment should be agreed and re-evaluated after treatment and where possible objective measures taken. Table 13.3.3 summarizes the oral drugs most commonly used in the treatment of spasticity. In the United Kingdom, baclofen is the drug most widely used in children with spasticity. Baclofen can also be of benefit for dystonia but the anticholinergic drugs, particularly trihexyphenidyl, are the mainstay of treatment. In a minority of patients a trial of L-dopa is indicated.

Oral baclofen has poor CSF penetration but baclofen can be administered directly into the CNS using an indwelling intrathecal catheter and implanted intra-abdominal reservoir. Thus effective drug doses are delivered to the target areas minimizing systemic side effects. Although the treatment is expensive and specialized, its benefits in spasticity management are well described. It is not yet widely available in the United Kingdom.

To target treatment to more focal areas of spasticity or dystonia, intramuscular injections with botulinum toxin (BTA) should be considered (see Chapter 13.4). ). BTA injections can be a valuable adjunct in the management of children with cerebral palsy, not just in improving function but also for comfort, cosmesis, and for ease of care.

For comprehensive management, specialist clinics for children with cerebral palsy play a valuable role; in particular combined neurology/orthopaedic clinics, feeding clinics, and clinics assessing and augmenting communication. Close working with Education and Social Services is crucial in supporting the child and family and furthering participation. In the United Kingdom, a Statement of Special Educational Needs provides an individual statutory assessment and agreed care package for the child within an Educational Setting. There are ongoing government initiatives looking at improving the integration of these services.

There are many alternative therapies on offer for families and children and with the increasing use of the Internet this is an area many families will explore. Information online is not always accurate and claims are not always realistic. Ideally this can be discussed openly with the doctors and therapists and advice and information shared. Support groups, in particular SCOPE, offer factsheets about many standard and more alternative treatments. They also run a helpline for children and families.

Transition into adult medical services can be difficult for the child and family and needs careful preplanning. Adult services do not offer the inclusive service seen in paediatric practice and care can often become fragmented.

Cerebral palsy remains a common condition. Whilst recent studies have improved our understanding of the associated risks and underlying causes we are still a long way from preventing its occurrence. It is important that clinical and scientific data can be shared between centres and increasingly, clinicians recognize that an agreed systematic approach to describing the clinical and scientific data collected is needed. This will allow further clarification of the causes and better evaluation of any management interventions.