Used in this book to denote disturbances of movement found in either organic or functional disorders.Akinesia is a reduction of voluntary movement ranging from moderate inactivity to total immobility. This condition is frequently observed in organic disorders of the brain, such as Pick’s disease and cerebral arteriosclerosis. In a rare brain disorder known as akinetic mutism, the patient lies with closed eyes, seldom moves or eats, and fails to respond to questions or stimuli. Among functional disorders, akinesia is most often observed in catatonic schizophrenia, retarded depression, and involutional psychotic reaction. The reduction in physical activity is usually accompanied by diminished mental activity, although in some involutional and schizophrenic patients there may be a profusion of ideas despite outward appearances. In schizophrenia the symptom may have symbolic significance: a motionless patient who holds one finger aloft for hours may be warning his countrymen of their sins or might even be immobilizing the armies of the world. Somewhat similarly, patients with idiopathic epilepsy may experience a transient “twilight state” in which they assume the role of God and strike a majestic pose. See TWILIGHT STATE.Hyperkinesia, or more usually hyperkinesis, refers to exaggerated motor activity and excessive restlessness. This symptom is also found in both physical and psychological disorders. It is one of the common effects of epidemic encephalitis. Some children classified as minimally brain damaged became so hyperactive that they are virtually unmanageable at home or in school. As to functional disturbances, children who live in a tense atmosphere often become restless and hyperactive, and in some cases they develop a character or behavior condition known as hyperkinetic impulse disorder, characterized—as the name implies—by extreme impulsiveness and overactivity.In childhood schizophrenia and catatonic excitement, hyperkinesis tends to take the form of unending repetition of stereotyped actions, such as rocking back and forth. In the manic phase of manic-depressive reaction it usually manifests itself in a ceaseless “pressure of activity.” Here the patient talks “a mile a minute,” moves restlessly about, writes dozens of letters, and pours forth an endless flow of unrealistic plans and ideas. See EPIDEMIC ENCEPHALITIS, BRAIN DYSFUNCTION, MANIC-DEPRESSIVE REACTION (MANIC PHASE), BEHAVIOR DISORDERS, SCHIZOPHRENIA (CATATONIC TYPE), SCHIZOPHRENIA (CHILDHOOD TYPE), STEREOTYPY.The term dyskinesia refers to distortions of voluntary movement, a common symptom in cerebral palsy. It is also applied to involuntary muscular activities such as tics, spasms and myoclonus (sudden contraction of a muscle in the limbs, body or face occurring in certain forms of petit mal or grand mal epilepsy).