What is cerebral palsy?

Cerebral Palsy: Clinical Overview

Definition

Cerebral palsy is a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain. 1 This is a clinical diagnosis, not a disease entity, encompassing heterogeneous motor impairments resulting from brain injury that is non-progressive in nature, though secondary complications can develop over time without appropriate intervention. 1

Epidemiology

• Prevalence: 2.1 cases per 1000 live births in high-income countries, making it the most common physical disability in childhood. 2, 3
• Declining trends: Prevalence is decreasing in Australia and Europe but remains higher in low- to middle-income countries due to greater infectious disease burden and differences in prenatal and perinatal care. 3
• High-risk populations: Among infants born weighing less than 1500 g, the frequency is 70 times higher compared to those weighing over 2500 g at birth. 4

Etiology and Risk Factors

The underlying cause remains uncertain in most cases, with birth asphyxia accounting for less than 10% of CP cases despite historical assumptions. 2 Recent evidence demonstrates that genetic factors contribute to 14% of cases, with exome sequencing yielding a diagnostic rate of 31.1% overall and 42.1% when patient selection criteria are applied. 2, 3

Key Risk Factors:

• Genetic: Rare genomic variants including copy number variants and single-nucleotide variants; monogenic and polygenic risks. 2, 5
• Maternal conditions: Thyroid disease, preeclampsia, infections. 3
• Pregnancy complications: Intrauterine growth restriction, multiple gestation, prematurity, low birth weight. 3, 6
• Preconception risks: History of stillbirths, miscarriages, low socioeconomic status, assisted reproduction. 3
• Postnatal: Infections, trauma, stroke, and hypoxic events in early infancy. 3

Clinical Classification

Motor Types (emerge and evolve during first 2 years):

• Spasticity: 85-91% of cases. 2, 3
• Dyskinesia: 4-7% (includes dystonia and athetosis). 2, 3
• Ataxia: 4-6%. 2, 3
• Hypotonia: 2%. 2, 3

Topographic Distribution (for spastic CP):

• Unilateral (hemiplegia): 38%. 2, 3
• Bilateral diplegia: 37% (lower limbs affected more than upper limbs). 2, 3
• Quadriplegia: 24% (all four limbs and trunk affected). 2, 3

Common Comorbidities

Cerebral palsy rarely occurs in isolation, with multiple disabling comorbidities that significantly impact quality of life:

• Chronic pain: 75%. 2, 3
• Epilepsy: 35-38%. 2, 3
• Intellectual disability: 27-49%. 2, 3
• Musculoskeletal problems (hip displacement): 28%. 2, 3
• Behavioral disorders: 26%. 2, 3
• Sleep disorders: 23%. 2, 3
• Speech disorders: 33-82%. 2
• Functional blindness: 11%. 2, 3
• Hearing impairment: 4%. 2, 3
• Autism spectrum disorder: 3-9%. 2

Diagnosis

Timing of Diagnosis

Diagnosis can now be made before 6 months' corrected age using standardized assessment tools in combination with clinical history, representing a significant advancement from the traditional 12-24 month diagnostic window. 2, 1

Diagnostic Tools Before 5 Months' Corrected Age:

• Term-age MRI: 86-89% sensitivity. 2, 1, 3
• Prechtl Qualitative Assessment of General Movements: 98% sensitivity (highest predictive value). 2, 1, 3
• Hammersmith Infant Neurological Examination: 90% sensitivity. 2, 1, 3

Diagnostic Tools After 5 Months' Corrected Age:

• MRI: 86-89% sensitivity (where safe and feasible). 2, 1, 3
• Hammersmith Infant Neurological Examination: 90% sensitivity. 2, 1, 3
• Developmental Assessment of Young Children: 83% C index. 2, 1

Neuroimaging Patterns

MRI findings most predictive for CP include:

• White matter injury (cystic periventricular leukomalacia or periventricular hemorrhagic infarctions): 56%. 3
• Cortical and deep gray matter lesions (basal ganglia, thalamus, watershed injury, multicystic encephalomalacia, stroke): 18%. 3
• Brain maldevelopments (lissencephaly, pachygyria, cortical dysplasia, polymicrogyria, schizencephaly): 9%. 3

Genetic Testing

Exome sequencing should be considered as standard of care for individuals with cerebral palsy, with an overall diagnostic yield of 31.1% (higher at 34.8% in pediatric populations and 42.1% when exclusion criteria are applied). 2 This yield is similar to other neurodevelopmental disorders for which exome sequencing is already recommended. 2

Management Principles

Early diagnosis and prompt referral to diagnostic-specific intervention is essential to optimize infant motor and cognitive plasticity, prevent secondary complications, and enhance caregiver well-being. 2, 3 Early intervention should begin as soon as CP is suspected rather than waiting for definitive diagnosis. 3

Critical Management Considerations:

• Delaying diagnosis and appropriate neurological management can be harmful to parent and caregiver well-being, potentially leading to depression and lasting anger. 3
• Early detection allows improved access to early intervention and efficient use of resources. 3
• Management requires a multidisciplinary team approach due to multiple associated medical conditions. 6
• Serial monitoring every 4-6 months is necessary to identify emerging muscle hypoextensibility and joint contractures. 7

Red Flags Suggesting Alternative Diagnosis:

• Loss of motor milestones (suggestive of neurodegenerative process). 3
• Respiratory insufficiency with generalized weakness. 3
• Motor delays present during minor acute illness. 3

Prognosis

In high-income countries, functional outcomes are better than historically assumed:

• 2 in 3 individuals with CP will walk. 2, 3
• 3 in 4 will talk. 2, 3
• 1 in 2 will have normal intelligence. 2, 3

Life Expectancy Considerations:

• Respiratory diseases and aspiration pneumonia are the leading causes of death, particularly in individuals with swallowing dysfunction. 3
• Early intervention programs that optimize neuroplasticity and prevent secondary complications can improve life expectancy. 3
• Better prevention and treatment of respiratory complications through early swallowing assessments and appropriate tube feeding when indicated can improve survival. 3

Key Clinical Pitfalls to Avoid

• Do not wait until 12-24 months to diagnose: Use standardized tools before 6 months' corrected age for earlier detection. 2, 1
• Do not attribute all cases to birth asphyxia: This accounts for less than 10% of cases; consider genetic testing. 2
• Do not rely on a single assessment: Use a combination of standardized tools in conjunction with clinical history. 2, 1
• Do not assume a single muscle group is responsible for limited motion: Combined contractures frequently coexist and require differentiated assessment. 7
• Do not delay intervention pending definitive diagnosis: Begin cerebral palsy-specific interventions as soon as CP is suspected. 3