Cerebral palsy

Cerebral palsy is a broad term for a group of permanent motor disorders that affect muscle tone, posture, and/or movement.

Cerebral palsy (CP) describes any non-progressive disorder of motor function that results from malformation or damage to the early developing brain. Therefore, it is an umbrella term for a heterogeneous group of conditions that cause permanent motor dysfunction due to injury in the prenatal, perinatal or early postnatal period. CP may occur alongside other major disorders of sensation, perception, cognition, communication, and behaviour.

CP is commonly multifactorial due to an acquired pathology (although some hereditary factors can increase the risk of developing CP). It is most commonly seen due to an abnormality or injury in the prenatal period with prematurity and/or low birth weight being the most common contributing factor.

The condition itself is characterised by abnormalities in muscle tone, posture, and/or movement that may lead to problems with early motor development that can lead to missing key developmental milestones. The condition is highly variable with different motor subtypes and it is associated with other disorders of cerebral function (e.g. learning difficulty).

The estimated prevalence of CP is 2.0 – 3.5 per 1000 live births but this number may be higher in resource-poor countries.

The major factor contributing to the development of CP is prematurity. An estimated 35% of infants born before 26 weeks gestation will develop CP. The overall prevalence of CP increases with decreasing gestational age and low birth weight.

Other risk factors have been linked to the development of CP but a definitive causal relationship has not been proved for all of them. Examples include heavy maternal alcohol consumption, maternal smoking, maternal obesity, intrauterine infection, placental abruption, and multiple pregnancy amongst many others.

The aetiology of CP is most often multifactorial with prematurity being commonly implicated.

CP is an acquired pathology due to an insult to the developing brain within the prenatal, perinatal or early infancy period. Many factors can cause abnormal cerebral development and often multiple causes are seen in combination.

The majority of cases of CP are due to prenatal events that cause an insult to the developing brain (e.g. haemorrhage, hypoxic injury, infection). It is estimated that < 20% of cases are due to a major postnatal event such as trauma or sepsis. The exact mechanisms leading to cerebral injury depend on the underlying cause and the time of injury. For example, injury in a premature infant may lead to periventricular leukomalacia (injury to cerebral white matter). The timing and type of injury will influence the clinical presentation of CP and associated higher cortical function deficits.

Aetiological factors include:

• Prematurity (and low birth weight)
• Perinatal hypoxic-ischaemic injury
• Congenital abnormalities
• Multiple births
• Stroke & intracerebral haemorrhage
• Intrauterine infection
• Maternal factors (e.g. seizure disorder, thyroid disorder)
• Genetic factors (some genetic factors predispose to CP)
• Postnatal event (e.g. trauma, kernicterus, sepsis, meningitis)
• Many other factors

NOTE: some infants may have an underlying genetic disorder that resembles the features of cerebral palsy (e.g. Lesch-Nyhan syndrome, Ataxia telangiectasia) that can be difficult to differentiate, especially if it is slowly progressive.

Prematurity

Prematurity is defined as birth before 37 weeks gestation. The earlier the premature date the higher risk of CP. It is estimated that up to 15% of infants surviving prematurity with very low birth weight (< 1500 g) will develop CP.

Prematurity is a significant risk factor due to the physical stress of being born immature on the already underdeveloped brain. There is a particular risk to areas of white mater around the ventricles that have important control in motor function and tone between 26-34 weeks gestation. Therefore, cerebral injury around this time due to underperfusion can cause periventricular leukomalacia (i.e. damage to the white mater). Other factors contributing to cerebral injury can include intraventricular haemorrhage and there is an association with bronchopulmonary dysplasia (underdeveloped lungs).

Perinatal hypoxic-ischaemic injury

In a minority of infants, a hypoxic-ischaemic event around the time of birth can lead to CP. Hypoxic-ischaemic events may occur due to severe placental abruption, ruptured uterus or amniotic fluid embolus, amongst others. There is subsequent development of neonatal encephalopathy, which is a heterogeneous condition that may also result from stroke, metabolic abnormalities or infection. It presents with a multitude of features including abnormal level of consciousness, seizures, tone and reflex abnormalities, apnea, aspiration, and feeding difficulties. These infants may go on to develop CP.

Congenital abnormalities

Congenital abnormalities are associated with the development of CP and may be seen in around 15% of cases. They refer to both abnormalities of the central nervous system (e.g. microcephaly, hydrocephalus) and the rest of the body (e.g. congenital heart disease). These congenital abnormalities may contribute to severe illness and injury during the prenatal, perinatal and postnatal periods.

Intrauterine infection

Many different types of infectious organisms can affect the growing foetus leading to subsequent CP. These can include bacterial infections, cytomegalovirus, varicella zoster, zika virus, and toxoplasmosis amongst others. In these infections, CP may be observed alongside other characteristic features as part of the infective syndrome.

CP commonly causes spastic motor weakness and/or paralysis.

Infants at risk of CP (e.g. prematurity, low birth weight, traumatic birth) should be closely monitored and are usually followed up by an enhanced clinical and developmental follow‑up programme.

Early features of CP

The diagnosis is usually made between 12-24 months of age. However, earlier diagnoses are frequently made. Early features that are suggestive of CP include:

• Abnormal movement: unusual fidgety movement, paucity of movement, asymmetrical movement
• Abnormal tone: floppy (hypotonia), stiff (spasticity), abnormal muscle contraction (dystonia – seen as a fluctuating tone)
• Retained or exaggerated developmental reflexes (i.e. motor reflexes related to posture)
• Feeding difficulties

Infants with CP may miss important developmental motor milestones (corrected for gestational age), which include:

• Not sitting by 8 months
• Not walking by 18 months
• Early asymmetry of hand function (hand preferences) before 12 months

Clinical subtypes

Depending on the clinical features, CP may be divided into different ‘subtypes’. This is traditionally based on the observed motor abnormalities but other methods have been used in modern practice.

A specific subtype can usually be identified after 18-24 months.

• Spastic (features of upper motor neurone weakness): increased tone, weakness, hyperreflexia, clonus
• Dyskinetic (involuntary movement): dystonia, choreoathetosis
• Ataxic (abnormal coordination): rare subtype

It is important to recognise while these subtypes are useful there is substantial overlap and features may change over time as the nervous system matures. These are discussed more in the chapter below on clinical subtypes.

Associated conditions

CP is commonly associated with many other disorders of cerebral function. Those with more severe motor abnormalities are more likely to have these other conditions. Examples include:

• Intellectual disability: seen in 50%. It is a type of neurodevelopment disorder with limitations in intelligence and adaptive skills (i.e. the ability to adapt to our environment). Severity correlate with degree of motor abnormalities
• Pain: seen in 50-75%. It can significantly affect quality of life. Around 25% of patients will have pain that limits activities
• Visual impairment: seen in up to 50%. Multiple abnormalities (e.g strabismus, refractive error, amblyopia)
• Epilepsy: seen in 25-45%. This is the propensity towards seizures. Partial seizures are most common due to focal brain injury
• Speech/language disorders: up to 25% are non-verbal
• Bladder control problems: frequent problems with enuresis (i.e bed-wetting), frequency, urgency, and incontinence
• Drooling: due to difficulty managing saliva (which is multifactorial) rather than overproduction
• Feeding difficulties: typically have growth failure and feeding difficulties due to abnormal suckling, crewing, and frequent choking. May require enteral feeding via a gastrostomy tube
• Other disorders: GI (e.g. constipation, reflux, abdominal pain), orthopaedic (e.g. contractures, hip dysplasia, scoliosis), sleep problems

Spastic CP is the most common subtype, which is characterised by upper motor neuron weakness.

There are three major subtypes of CP based on motor abnormalities, which include:

• Spastic (features of upper motor neuron weakness)
• Dyskinetic (involuntary movement)
• Ataxic (abnormal coordination)

Spastic

Spastic CP is characterised by upper motor neuron weakness, which refers to increased tone, weakness, hyperreflexia, and clonus Spasticity is essentially high tone that is velocity-dependent. This means there is increased resistance in response to passive stretching of the affected muscles. In its severe form, the affected muscles are held in fixed flexion or extension

There are three major types of spastic weakness that are seen in cerebral palsy. The clinical features of these types are different in infants and young children compared to older children > 5 years old. Here, we discuss the typical findings in older children:

• Spastic diplegia: Predominant involvement of lower limbs. Hips are flexed, adducted, and internally rotated with contractures affecting the hip flexors and hamstrings. Gait often described as scissoring
• Spastic hemiplegia: Only one side of the body is affected. The arm is affected more than the leg. The shoulder is usually adducted, elbow flexed, forearm pronated and wrist/fingers flexes with hand closed. The hip is usually partially flexed and adducted with the knee and ankle flexed. The foot may point downwards in equinovarus position
• Spastic quadriplegia: All the limbs are affected. Children are typically severely handicapped with multiple associated conditions

A variety of so-called ‘negative’ signs also occur in spastic CP that often cause more disability. These relate to poor control or insufficient muscle activity. They can include slow, effortful movement, loss of dexterity, or difficult to isolate individual movements.

Dyskinetic

Dyskinesia refers to involuntary muscle movement. This type of movement can occur in children with spastic features. It is broadly divided into two types:

• Choreoathetosis: Describes two major movements. The abnormal chorea movements consist of rapid, irregular, unpredictable contractions of muscles, and the abnormal athetosis movements consist of slow, smooth, writhing movements. Chorea movements typically involve the face, bulbar muscles, proximal limbs, fingers, and toe. Athetosis movements usually involve distal muscles. These movement abnormalities are often exacerbated by emotion, stress, environmental stimuli, or fever
• Dystonia: characterised by involuntary, sustained muscle contraction. Causes repetitive movements or postures and often changes depending on the activity or posture

Ataxic

This is a rare type of CP that causes abnormal muscle coordination. Other features may include early delay in language skills and later slow, jerky and explosive speech. If it is purely ataxic, it’s important to exclude genetic causes that may present similarly to ataxic CP.

The diagnosis of CP is clinical and should involve a full developmental assessment.

CP is a clinical diagnosis based on a full medical assessment. This should include a detailed history to determine any major risks for developing CP (e.g. antenatal history, birth history, family history, etc) and a physical examination including a full developmental assessment (e.g. documenting developmental milestones).

A definitive diagnosis often requires serial assessments and most cases can be diagnosed by two years of age. Features supportive of the diagnosis of CP include:

• Abnormal motor development and posture
• Brain injury is permanent and nonprogressive
• Motor impairment is attributed to an insult that occurred in the developing foetal or infant brain
• Motor impairment results in limitations in functional abilities and activity
• Motor impairment is often accompanied by other disorders of cerebral function (e.g. intellectual disability, epilepsy, speech impairment)

Additional testing

Additional tests may be requested based on the suspected aetiology and to exclude alternative causes (e.g. genetic/metabolic testing). Neuroimaging (e.g. MRI brain), if not already completed during infancy, is commonly requested if the aetiology has not been established. Children more severely affected may require early assessment with neuroimaging.

It is important to highlight that CP is non-progressive. If there is evidence of progressive deterioration then an alternative condition should be investigated (e.g. neurodegenerative disorder). Many conditions that are slowly progressive may be misdiagnosed as CP.

If cerebral palsy is suspected

Infants at risk of CP are usually followed up in an enhanced clinical and developmental follow‑up programme so an early diagnosis can be established. Outside of this, children with suspected CP should be referred to a child development service so they can undergo a full multidisciplinary assessment.

Infants and children with suspected CP may include:

• Risk factors for CP
• Abnormal motor features
• Delayed motor milestones
• Persistent toe walking

Screening for associated conditions

CP is associated with many other disorders of cerebral function. It is important that these are also assessed and tested for during the work-up of infants and children. For example, standardised screening tools can be used for intellectual disability, an EEG may be used to aid the diagnosis of epilepsy, and children should undergo both visual and audiological assessments.

Infants and children with CP should be managed by a specialist multidisciplinary team.

Infants and children with CP will have a wide spectrum of severity and health needs. Due to the differing severity and associated disorders of cerebral function, a wide number of health care professionals are usually required to provide the care needed for each child.

The best way to provide this is through a multidisciplinary team. This team may involve:

• Community paediatrician
• Neurologist
• Physiotherapy
• Occupational therapy
• Speech and language therapy
• Dietitian
• Psychologist
• General practitioner

This is not an exhaustive list and many other healthcare professionals may be involved. It is not possible to give a comprehensive outline of the management for every issue in cerebral palsy, but note that a structured approach to each condition or clinical feature involving conservative, medical, or even surgical treatments can greatly improve the individuals’ quality of life.

Medical management

Medical therapies can be important in the management of CP depending on the clinical features and associated conditions. These may include:

• Anti-cholinergic agents (e.g. hyoscine hydrobromide): for drooling
• Laxatives (e.g. movicol): for constipation
• Percutaneous endoscopic gastrostomy (PEG): for nutrition
• Anti-epileptics (e.g. Keppra): for epilepsy
• Anti-spasmodics (e.g. Baclofen, Botox injections): for spasticity
• Analgesia (e.g. paracetamol): for chronic pain

The choice of therapy should be targeted towards the needs of the patient.

Surgical management

Surgery may be an option in certain situations for individuals whose symptoms are refractory to conservative and medical therapies. Common indications include orthopaedic surgery for hip dysplasia or severe contractures and maxillofacial/ENT surgery for disabling drooling.

CP is a permanent condition and most children will survive to adulthood.

CP is a non-progressive condition but the neurological and functional implications of CP may evolve over time. The majority of children with CP will survive to adulthood but the overall life expectancy is reduced. In general, those with more severe or disabling symptoms have a shorter life expectancy. The most common cause of death in these patients is respiratory complications such as aspiration pneumonia. The extent of motor difficulty can be hard to predict during early childhood but several prognostic factors can help predict walking and speech development (e.g. If a child cannot sit or roll at 2 years of age, they are unlikely to be able to walk unaided).