palsy: see paralysis.

cerebral palsy, disability caused by brain damage before or during birth or in the first years, resulting in a loss of voluntary muscular control and coordination. Although the exact cause is unknown, apparent predisposing factors include disease (e.g., rubella, genital herpes simplex), very low infant birthweight (less than 3.3 lb [1.5 kg]), and injury or physical abuse. Maternal smoking, alcohol consumption, and ingestion of certain drugs can also contribute. Most cases are associated with prenatal problems; about 10% of the cases are thought to be due to oxygen deficiency during the birth process. The severity of the affliction is dependent on the extent of the brain damage. Those with mild cases may have only a few affected muscles, while severe cases can result in total loss of coordination or paralysis.

There are many different forms of the disability, each caused by damage to a different area of the brain. The spastic type, accounting for over half of the cases, results from damage to the motor areas of the cerebral cortex and causes the affected muscles to be contracted and overresponsive to stimuli. Athetoid cerebral palsy, caused by damage to the basal ganglia, results in continual, involuntary writhing movements. Choreic cerebral palsy is characterized by jerking, flailing movements. Ataxic cerebral palsy, involving the cerebellum, causes either an impaired sense of balance or a lack of coordinated movements. In addition to these types, which may occur singly or together, emotional, visual, and hearing impairments and convulsive seizures may be present. Some of those affected have a degree of mental retardation, but in many the intellect is unimpaired.

There is no cure for the disorder. Treatment usually includes physical, occupational, and speech therapy, and sometimes includes biofeedback and muscle relaxants. Sometimes appliances such as braces and surgery are helpful. Measures that appear to help decrease the incidence of cerebral palsy include maternal immunization against rubella, maternal abstention from smoking and alcohol consumption, magnesium sulfate given in premature labor, treatment for Rh incompatibility (see blood groups), and treatment of hyperbilirubinemia (jaundice) in the newborn.

Neurological disorder causing progressive loss of control of movement. It was first described in 1817 by British physician James Parkinson (1755–1824). The cause of primary parkinsonism, or Parkinson disease, is unknown. The mean age of onset is about 57, but juvenile parkinsonism is also known. Neurons in the brain that normally produce dopamine deteriorate. When 60–80percnt are destroyed, signals suppressing unintended movement are disrupted and symptoms appear, including tremor at rest, muscle rigidity, trouble in starting movements, and loss of balance. Known causes include sleeping sickness; certain poisons; repeated blows to the head, as in boxing; and the drug MPTP. Environmental toxins or genetic susceptibility may account for some cases. Drug therapy requires careful scheduling and combinations to delay development of tolerance and side effects. Surgical pallidotomy (destruction of the globus pallidus, a brain structure involved in motor control) and transplantation of fetal dopamine-producing tissue remain experimental.

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or palsy

Loss or impairment of voluntary use of one or more muscles. It may be flaccid (with loss of muscle tone) or spastic (stiff). Hemiplegia (one-sided paralysis) is usually caused by stroke or brain tumour on the opposite side. Diplegia (two-sided paralysis, as in cerebral palsy) results from generalized brain disease. Spinal-cord damage (from bone or joint disease, fracture, or tumour affecting the vertebrae; inflammatory and degenerative diseases; or pernicious anemia) paralyzes the body at and below the level of the damage (paraplegia if the legs and lower body only; quadriplegia if arms and legs). Poliomyelitis and polyneuritis (neuritis of multiple nerves) result in paralysis with muscle wasting. Bell palsy (a type of neuritis) paralyzes the muscles of one side of the face. Muscular dystrophy causes paralysis by attacking muscle. Metabolic causes include myasthenia gravis. Paralysis may also have psychiatric causes (see hysteria).

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Paralysis resulting from abnormal development or damage to the brain before or soon after birth. Cases are of four main types: spastic, with spasms contracting the extremities and often also with intellectual disability and epilepsy; athetoid, with slow, changing spasms in the face, neck, and extremities, grimacing, and inarticulate speech (dysarthria); ataxic, with poor coordination, muscle weakness, an unsteady gait, and difficulty performing rapid or fine movements; and mixed, in which symptoms of two or more types are present.

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