spastic paralysis, form of paralysis in which the part of the nervous system that controls coordinated movement of the voluntary muscles is disabled. In spastic paralysis the nerves controlling muscle movement are hyperirritable and do not function in a coordinated manner, so that impulses from them cause spasmodic muscle contraction. Extreme spastic paralysis occurs after various kinds of brain damage, e.g., stroke. Spinal cord injury, such as that produced by inflammatory diseases of nerve tissue, can injure motor neuron fibers in the spine and cause spastic paralysis. Congenital spastic paralysis, or cerebral palsy, is often a result of intrauterine disease or birth injury, or occasionally some inherited nervous system defect.

paralysis or palsy, complete loss or impairment of the ability to use voluntary muscles, usually as the result of a disorder of the nervous system. The nervous tissue that is injured may be in the brain, the spinal cord, or in the muscles themselves. Accordingly there may be general paralysis, involvement of only one side (hemiplegia), paralysis on both sides at one level (paraplegia or quadriplegia), or localized paralysis in a small group of nerves or muscles.

The cause of paralysis may be any injury that tears or compresses the nerves; it may be hemorrhage, tumor, infection, or substances toxic to nerve tissue. One of the most frequent causes of paralysis is stroke, in which hemorrhage, thrombosis, or obstruction of a cerebral vessel interferes with nerve function. Another disorder in which a resting tremor is one of the main symptoms, accompanied by slowness and poverty of movement, muscular rigidity, and postural instability is Parkinson's disease. Cerebral palsy is due to an injury to the brain motor tissue before or during birth. However, this disorder is nonprogressive. Partial or complete paralysis often accompanies multiple sclerosis.

infantile paralysis: see poliomyelitis.

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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or polio or infantile paralysis

Acute infectious viral disease that can cause flaccid paralysis of muscles. Severe epidemics killed or paralyzed many people, mostly children and young adults, until the 1960s, when Jonas Salk's injectable killed vaccine and Albert B. Sabin's oral attenuated live vaccine controlled polio in the developed world. Flulike symptoms with diarrhea may progress to back and limb pain, muscle tenderness, and stiff neck. Destruction of spinal cord motor cells causes paralysis, ranging from transient weakness to complete, permanent paralysis, in fewer than 20percnt of patients. Patients may lose the ability to use their limbs, to breathe, or to swallow and speak. They may need physical medicine and rehabilitation, mechanical breathing assistance, or tracheal suction to remove secretions. A “postpolio syndrome” occurs decades later in some cases, with weakness of muscles that had recovered.

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