Cerebral Palsy

Definition

Cerebral palsy (CP) is defined as 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. Onset is before age 2 years. Despite the brain lesion being static and non-progressive, the musculoskeletal consequences (contractures, deformities, scoliosis, hip dislocation) do worsen over time.

Bradley and Daroff's Neurology in Clinical Practice, p. 2040
Goldman-Cecil Medicine, p. 4048

Epidemiology

Prevalence: approximately 2-3 per 1,000 live births
Most common physical disability of childhood
Prevalence initially decreased in the 1950s-60s with improved management of Rh incompatibility and obstetric care
Improved survival of premature/low-birth-weight infants has not significantly increased overall prevalence in population-based studies

Etiology & Risk Factors

Cause is often not identifiable, but known causes include:

Category	Examples
Prematurity	Most common; periventricular leukomalacia (PVL)
Perinatal hypoxia-ischemia	Birth asphyxia in term/near-term infants
Prenatal/intrauterine	Congenital brain malformations (e.g., absent corpus callosum), TORCH infections
Perinatal infections	Toxoplasmosis, rubella, CMV, herpes simplex
Vascular	Perinatal stroke, intracranial hemorrhage
Metabolic/toxic	Kernicterus (bilirubin toxicity to basal ganglia)
Genetic	~20% idiopathic; ~1/3 of idiopathic cases have de novo copy number variants; ~14% may have single-gene disorders on whole exome sequencing
Post-natal	Meningitis, anoxic injury in infancy

Note: ~20% of cases remain idiopathic. A growing fraction have underlying genetic etiologies, including inborn errors of metabolism - some of which are treatable.

Classification

1. Physiologic (Motor Type)

Spastic (80% of all cases) - injury to the pyramidal (corticospinal) tracts

Velocity-dependent increase in muscle tone with passive stretch
Co-contraction of antagonist muscle groups
Leads to joint contractures, subluxation, degeneration
Collagen deposition (type I) in endomysium of affected muscle causing fibrosis

Dyskinetic / Extrapyramidal (involves basal ganglia/cerebellum)

Dystonia - sustained or repetitive muscle contractions, twisting/abnormal postures
Athetosis - slow, writhing, involuntary movements
Chorea - rapid, irregular, involuntary movements
Ataxia - cerebellar-type with balance/coordination problems
Spastic diplegia usually detected at 8-10 months; hemiplegia ~20 months; athetoid type after 24 months

Mixed - combination of movement disorder types

2. Anatomic (Topographic) Distribution

Type	Distribution	Key Features
Hemiplegia	One side, arm > leg	~30% of CP; sensory changes common; leg-length discrepancy possible
Diplegia	All 4 limbs, legs >> arms	~50% of CP; most common in premature infants; usually normal intelligence; most walk by age 4
Quadriplegia	All 4 limbs equally	Significant cognitive deficits frequent; head/neck control usually present
Total body	All limbs + head/neck	Profound cognitive deficits; drooling, dysarthria, dysphagia; requires full-time care

3. Functional Classification - GMFCS

The Gross Motor Function Classification System (GMFCS) is the most widely used system, stratifying children by self-initiated movement with emphasis on sitting, walking, and wheeled mobility:

GMFCS Expanded & Revised - 5-level classification system

Level I - Walks without restrictions; limitations in advanced gross motor skills
Level II - Walks with limitations; difficulty with uneven terrain, long distances
Level III - Walks with hand-held mobility device; wheelchair for long distances
Level IV - Self-mobility limited; requires powered mobility or physical assistance
Level V - Transported in manual wheelchair; very limited self-mobility

GMFCS has been shown to be predictive of hip dislocation risk. It is reliable and stable for children up to 18 years.

The Manual Abilities Classification System (MACS) is an analogous 5-level system for upper-extremity function in children 4-18 years.

Neuroimaging

Brain MRI is preferred over head ultrasound and is considered essential in evaluation:

Spastic diplegia: periventricular leukomalacia (PVL) - white matter injury near ventricles
Spastic hemiplegia: perinatal stroke evidence
Dyskinetic CP: involvement of thalamus and basal ganglia (especially lenticular nucleus) in ~70% of cases; globus pallidus involvement in kernicterus
Normal MRI (~13% of dyskinetic CP): raises concern for underlying genetic/metabolic condition requiring further workup

Diagnosis

CP is a clinical diagnosis based on:

History - perinatal/postnatal brain injury risk factors; exposure history
Physical examination - abnormal tone, deep tendon reflexes, pathological reflexes, motor delay
Neuroimaging - MRI brain to define type and extent of injury

Differentiating Genetic from Acquired CP (3-step approach):

Step 1: Does history + examination + MRI fit a known mechanism of brain injury?
Step 2: If MRI is normal or atypical, or course is unusual, pursue genetic workup (chromosomal microarray, metabolic screen, whole exome sequencing)
Step 3: Consider treatable metabolic mimics (dopa-responsive dystonia, neurotransmitter disorders, some leukodystrophies)

Clinical Features & Comorbidities

Exaggerated deep tendon reflexes, clonus, pathological reflexes (Babinski)
Spasticity leading to progressive contractures and deformity
~50% have cognitive impairment (sometimes severe)
Epilepsy (~25-35%)
Speech and language disorders (dysarthria, dysphagia)
Visual impairment, strabismus
Drooling
Pain (increasingly recognized, particularly in adults)
Bladder dysfunction

Treatment

CP treatment is multidisciplinary and targets motor function, spasticity, pain, and functional independence.

Spasticity Management

Approach	Details
Physical/occupational therapy	Core of management; gait training, stretching
Oral medications	Baclofen, benzodiazepines, tizanidine, trihexyphenidyl (for dystonia)
Botulinum neurotoxin (BoNT/Botox)	Targeted intramuscular chemodenervation; especially useful for focal spasticity
Intrathecal baclofen (ITB)	Pump delivers baclofen directly to CSF; highly effective for generalized spasticity; GMFCS III-V
Selective dorsal rhizotomy (SDR)	Resection of 25-40% of abnormal dorsal nerve rootlets; ideal candidates are age 4-10, GMFCS I-III, with PVL on MRI; irreversible
Deep brain stimulation (DBS)	Primarily for dyskinetic/dystonic CP

SDR is cheaper than ITB long-term and has shown functional ambulation gains in GMFCS I-III patients with continued benefit into adolescence.

Orthopedic Interventions

Hip surveillance - regular radiographs; higher risk at GMFCS IV-V; adductor releases to prevent hip subluxation/dislocation
Scoliosis/spinal deformity - common in quadriplegic/total body CP; managed with bracing or spinal fusion
Lower limb surgery - hamstring lengthening, calf muscle lengthening, tibialis posterior transfer; aim for plantigrade foot and improved gait
Gait analysis - used as an essential tool to guide surgical planning; assesses kinetics and kinematics

Goals by Severity

Ambulatory patients (GMFCS I-III): Optimize gait, prevent/correct contractures, maximize independence
Non-ambulatory (GMFCS IV-V): Straight spine, level pelvis, seated hip stability (90° flexion), plantigrade feet, appropriate wheelchair seating

Recent Evidence Updates

Three recent systematic reviews (2025) worth noting:

Extracorporeal shock wave therapy for motor function in CP - emerging evidence for motor outcomes (PMID 40481808)
Genetic findings in CP have clinical actionability in a clinically meaningful proportion of patients, supporting expanded genetic testing (PMID 39621323, JAMA Pediatrics 2025)
Pain in adults with CP is common and underrecognized (PMID 39937705)

Sources: Campbell's Operative Orthopaedics 15th Ed 2026 | Bradley and Daroff's Neurology in Clinical Practice | Goldman-Cecil Medicine | Miller's Review of Orthopaedics 9th Ed

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