convulsion, sudden, violent, involuntary contraction of the muscles of the body, often accompanied by loss of consciousness. It is not known what causes the abnormal impulses from the brain that result in convulsive seizures, since the disturbance may arise in normal brain tissue as well as in diseased or injured tissue. Convulsions may occur in such conditions as epilepsy, poisoning, high fever (especially in young children), disturbances of calcium or phosphorus metabolism, alkalosis, diabetes, oxygen insufficiency, and a low blood-sugar content, as well as in local irritation or injury of the brain. Persons undergoing convulsions should be guarded against self-injury (see epilepsy). Otherwise, treatment must be directed to the underlying cause.