Cerebral Palsy

Definition:

A group of disorders characterized by loss of movement or loss of other nerve functions. These disorders are caused by injuries to the brain that occur during fetal development or near the time of birth.

Causes, incidence, and risk factors:

The incidence of cerebral palsy is approximately 2 to 4 individuals for every 1000 births. Cerebral palsy results from injury to the cerebrum (the largest portion of the brain, involved with higher mental faculties, sensations, and voluntary muscle activities).

Initially cerebral palsy was thought to be related to birth asphyxia and trauma but in a study of 45,000 births it was shown that birth asphyxia is an uncommon cause of cerebral palsy. The cause of hypoxia (low oxygen) to the damaged areas of the brain has not been adequately made clear, but it is believed that there are predisposing factors occurring during the development of the fetus that makes it more susceptible to hypoxia. Premature infants have a slightly higher incidence of cerebral palsy. Cerebral palsy may also occur during early infancy as a result of cerebral injury caused by illnesses (encephalitis, meningitis, herpes simplex infections, and so on), head injury that results in subdural hematoma, blood vessel injuries, and many others.

Injury to the cerebrum can result in the loss of nerve functions in widely different areas. The classical finding of CP is spasticity (increased muscle tone) which may affect a single limb, one side of the body (spastic hemiplegia), both legs (spastic diplegia) or both arms and legs (spastic quadriplegia). In addition there may be partial or full loss of movement (paralysis), sensory abnormalities, and defects of hearing and vision. Speech abnormalities are common and seizures may occur. Intellectual function may range from extremely bright normal to severe mental retardation. Symptoms are usually evident before age 2 and in severe cases may appear as early as three months. Cerebral palsy is a non-progressive type of encephalopathy (injury to the brain) and symptoms directly resulting from the disease do not worsen.

Classifications of cerebral palsy include spastic, dyskinetic, ataxic, and mixed cerebral palsy. Spastic cerebral palsy includes about 50% of cases. Dyskinetic (athetoid) cerebral palsy affects about 20%. It involves development of abnormal movements (twisting, jerking, or other movements). Ataxic cerebral palsy involves tremors, unsteady gait, loss of coordination, and abnormal movements. It affects about 10%. The remaining 20% are classified as mixed, with any combination of symptoms.