Cerebral palsy

What it is

Cerebral palsy describes a group of permanent disorders of movement and posture that limit activity and are attributed to non-progressive disturbances in the developing fetal or infant brain. These movement problems are often accompanied by difficulties with sensation, perception, thinking, communication and behaviour, by epilepsy, and by secondary musculoskeletal problems².

It is a clinical description rather than a single disease: the type of movement disorder, the parts of the body affected and the degree of ability vary greatly¹. The brain injury itself does not get worse, but its effects on muscles and joints can change as a child grows^1,4.

In high-income countries, the birth prevalence of cerebral palsy caused before or around birth has fallen in recent decades³.

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White matter around the ventriclesMotor cortexBasal ganglia and thalamusCerebellum

Damage to the white matter around the fluid-filled ventricles is typical in babies born preterm^14,15. Fibres carrying movement signals from the cortex pass through this region.

The motor cortex and its pathways control voluntary movement; injury to them disrupts muscle tone, leading to spasticity^1,2,14.

Oxygen deprivation around birth at term can damage deep grey matter such as the basal ganglia and thalamus^14,16. Injury to these structures is typically associated with dyskinetic forms¹⁷.

The cerebellum coordinates movement. Ataxic forms are thought to involve it, although brain scans of children with ataxic cerebral palsy are often normal¹⁸.

Signs and symptoms

Signs usually emerge and evolve during the first two years of life⁵. Babies may be slow to roll over, sit, crawl or walk, may feel unusually floppy or stiff, or may favour one side of the body⁴. Cerebral palsy is classified by the main type of movement problem: spastic (stiff muscles), which is the most common, dyskinetic (involuntary writhing or jerky movements), ataxic (poor balance and coordination), or mixed⁴.

• Muscle stiffness and exaggerated reflexes (spasticity), or floppy muscle tone⁴
• Weakness affecting one side of the body, mainly the legs, or all four limbs⁴
• Unusual walking patterns, such as walking on tiptoe or with a crouched or scissored gait⁴
• Delayed motor milestones and difficulty with fine hand movements⁴
• Associated conditions such as epilepsy, intellectual or learning difficulties, and problems with hearing, vision, speech and swallowing^1,4
• Later problems such as hip displacement, scoliosis (curvature of the spine) and pain^1,4

Causes and risk factors

Most cerebral palsy is congenital, meaning the brain injury or difference occurs before or around birth; a smaller number of cases are acquired after birth, for example through brain infection, stroke or head injury⁴. In many cases a single cause cannot be identified⁴.

• Premature birth and low birthweight⁴
• Twin, triplet and other multiple births⁴
• Infections during pregnancy, such as cytomegalovirus, rubella, toxoplasmosis and Zika virus⁴
• Reduced oxygen supply to the baby’s brain around birth (hypoxic-ischaemic injury)¹⁰
• Stroke in the baby before or soon after birth⁴
• Genetic variants, increasingly recognised in children without traditional risk factors^10,11

Genetics

As many as one-third of children with cerebral palsy have none of the traditional risk factors such as prematurity or oxygen deprivation, and in many of them a genetic basis is suspected¹⁰.

Whole-exome sequencing, which reads the protein-coding parts of all genes, of 250 children and their parents found an excess of new (de novo) damaging mutations. Two genes, TUBA1A and CTNNB1, reached genome-wide significance, and the authors estimated that about 14% of cases could be attributed to damaging de novo or recessive variants¹¹.

Many of the genes involved overlap with those linked to other neurodevelopmental disorders and affect how nerve cells form connections¹¹. Genetic findings can matter for families, because they may change advice about recurrence and care. The field is still developing, and most cerebral palsy is not inherited.

What happens in the brain

Cerebral palsy results from injury to, or abnormal development of, the brain areas and pathways that control movement, while the brain is still developing^1,2. Common patterns include damage to the white matter around the fluid-filled ventricles, typical in babies born preterm, damage to deep grey matter such as the basal ganglia and thalamus after oxygen deprivation around birth at term, and injury from stroke^14,15,16.

Damage to the motor pathways, which run from the motor cortex past the ventricles to the spinal cord, disrupts the signals that normally regulate muscle tone, leading to spasticity¹⁴. Injury to the basal ganglia and thalamus, deep structures that help control movement, is typically associated with dyskinetic forms¹⁷. Ataxic forms, with poor balance and coordination, are thought to involve the cerebellum, which coordinates movement, although brain scans are often normal¹⁸.

Over time, abnormal muscle tone and weakness can cause muscles to shorten (contractures) and bones and joints to develop abnormally, for example hip displacement and scoliosis^1,4,14.

How it is diagnosed

Diagnosis was historically made between 12 and 24 months of age, but with standardised tools it can now be made accurately before 6 months’ corrected age (age adjusted for prematurity) in high-risk infants⁵. Early diagnosis allows early intervention while the brain is most adaptable⁵.

• Detailed history of pregnancy, birth and development, and regular monitoring of motor skills, tone, posture, hearing and vision^4,5
• MRI of the brain, which detects risk with about 86–89% sensitivity⁵
• The Prechtl General Movements Assessment, a video-based assessment of spontaneous movements in young infants, with about 98% sensitivity before 5 months⁵
• The Hammersmith Infant Neurological Examination, a standardised clinical examination⁵
• The Gross Motor Function Classification System, which grades mobility into five levels to describe severity⁶
• Genetic testing in selected children, particularly when there are no clear risk factors^10,11

How scientists study it

Current treatments

Research frontiers

Living with the condition and seeking help

Many people with cerebral palsy lead full, independent lives, while others need substantial support. Care is usually coordinated by a multidisciplinary team, and in the United Kingdom NICE guidance emphasises giving families clear information and support¹².

Parents who are concerned about a baby’s movements, muscle tone or delayed milestones should speak to a family doctor, paediatrician or child health worker, as early assessment allows early intervention⁵. In India, the Rashtriya Bal Swasthya Karyakram screens children for motor and other developmental delays and refers them to District Early Intervention Centres¹⁹.

Urgent medical help should be sought for a prolonged seizure, breathing or swallowing difficulty, or a sudden change in ability or alertness. In India, the national emergency number is 112 and the ambulance number is 108^20,21.