Definition of cerebral palsy

The term cerebral palsy (CP) was originally coined more than a century ago and loosely translates as "brain paralysis." However, a precise definition has remained elusive because CP is not a single diagnosis but an "umbrella" term describing nonprogressive brain lesions involving motor or postural abnormalities that are noted during early development . CP has been described as follows:

A group of disorders of the development of movement and posture causing activity limitations that are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain. The motor disorders of cerebral palsy are often accompanied by disturbances of sensation, cognition, communication, perception, and/or behavior and/or a seizure disorder.

Age of onset

The brain lesions of CP occur from the fetal or neonatal period to up to age 3 years. Insults to the brain after age 3 years through adulthood may manifest clinically as similar or identical to CP, but, by definition, these lesions are not CP. Although the lesion to the developing brain occurs prior to age 3 years, the diagnosis of CP may not be made until after that time. Some authorities advocate not making a definitive diagnosis in some cases until age 5 years or later. This approach allows the clinical picture to be clear and potentially allows exclusion of progressive diseases . In addition, some children have been diagnosed with CP at an early age, only to have the symptoms resolve later .

Lesion location

CP is restricted to lesions of the brain only; diseases specific to the peripheral nerves of the spinal cord (eg, spinal muscular atrophy, myelomeningocele) or to the muscles (eg, muscular dystrophies), although causing early motor abnormalities, are not considered CP.

Associated findings

Approximately 30-50% of patients with CP have mental retardation, depending on the type of CP. However, because of oromotor, fine motor, and gross motor difficulties, communication in CP patients may be impaired and expression of intellectual capacity may be limited. However, if CP is approached in a multidisciplinary manner, with physical, occupational, and nutritional therapy to maximize rehabilitative efforts, patients can be more fully integrated academically and socially.

Approximately 15-60% of children with CP have epilepsy, and epilepsy is more frequent in patients with spastic quadriplegia or mental retardation.

Etiology and risk factors

The etiology of CP is not well understood, and brain lesions are thought to be associated with prenatal, perinatal, or postnatal events of varying causes. Risk factors for CP are multifactorial and can include preterm birth, multiple gestation, intrauterine growth restriction, male sex, low Apgar scores, intrauterine infections, maternal thyroid abnormalities, prenatal strokes, birth asphyxia, maternal methyl mercury exposure, and maternal iodine deficiency.

Classification and types

CP is classified according to resting tone and what limbs are involved (called topographic predominance). Spastic CP, due to cortex/pyramidal tract lesions, is the most common type and accounts for approximately 80% of cases . Spastic CP is characterized by spasticity (velocity-dependent increase in tone), hyperreflexia, clonus, and an upgoing Babinski reflex. Extrapyramidal or dyskinetic CP is characterized more by abnormal involuntary movements.

Typical types of CP

* Spastic hemiplegia - CP predominantly affecting one side of the body, with upper extremity spasticity more than lower extremity spasticity (eg, right side involved with right arm more so than right leg)

* Spastic diplegia - CP affecting bilateral lower extremities more than upper extremities

* Spastic quadriplegia - CP affecting all 4 extremities (full body)

* Dyskinetic CP (athetoid CP, choreoathetoid CP, and dystonic CP) - CP with extrapyramidal signs characterized by abnormal movements; hypertonicity often is associated

* Mixed CP - CP with no single specific tonal quality predominating; typically characterized by a mixture of spastic and dyskinetic components

* Hypotonic CP - CP with truncal and extremity hypotonia with hyperreflexia and persistent primitive reflexes; thought to be rare