CHOREA

also called Hyperkinesia, in dogs, a disorder in which muscle spasms are prominent. It is usually associated with distemper, encephalitis, or other diseases and often appears during the convalescent period. Jaw spasms may interfere with eating, and extreme exhaustion follows severe episodes in which the dog cannot sleep. Treatment involves good nutrition, vitamin supplements, and sedation. Antispasmodic drugs and muscle relaxants are used to relieve the symptoms. neurological disorder characterized by irregular, involuntary, and purposeless movements of muscle groups in various parts of the body. The principal types of chorea are Sydenham's chorea (St. Vitus' dance) and Huntington's chorea. Sydenham's chorea is usually associated with rheumatic fever and is sometimes called chorea minor, infectious chorea, or rheumatic chorea to distinguish it from other choreiform diseases. The name St. Vitus' dance derives from the late Middle Ages, when persons in the grip of the disorder attended the chapels of St. Vitus, who was believed to have curative powers. In Sydenham's chorea the involuntary jerking movements are most obvious in the extremities and face but are also present in the trunk and may involve muscles of speech and swallowing. It is chiefly a disease of childhood, occurring most frequently between the ages of 5 and 15 years, and is more common in girls than in boys. It may occur in young adults and is an infrequent complication of pregnancy, when it is especially severe. Because more than 70 percent of cases of chorea are clinically associated with rheumatic fever, it may be considered a peculiar manifestation of that disease; it is estimated that 50 percent of children who have had rheumatic fever also develop chorea. While emotional crises and anxiety may appear to be intimately related to the onset of Sydenham's chorea, they are actually a manifestation of the disease rather than a cause of it. Facial grimaces, tics, and habit spasms are frequently confused with chorea, but these repetitive movements are quite different from the uncoordinated, purposeless jerking movements of the disease. The latter, which are typical and recognizable, are usually preceded by or appear with evidence of irritability and emotional instability, chiefly episodes of crying initiated by trivial incidents. The symptoms of chorea range in severity from mild to completely incapacitating. The inability to hold objects or to write properly and difficulty in walking are frequent. A vague deterioration in the ability to perform customary tasks is soon replaced by the gross twitching of muscle groups, most easily observed in the limbs. The movements are more marked on the limbs of one side of the body but are present on both. While there is debate concerning the pathological changes in the central nervous system, there is considerable evidence that both the emotional manifestations and the typical movements are related to changes in the cerebral cortex. It is thought that the disease is caused by a malfunctioning of the neuronal circuits of the basal ganglia. Attacks of Sydenham's chorea tend to be self-limited, although the duration is several weeks. Recurrence is frequent. Recovery is hastened by rest in bed in a pleasant, sympathetic environment; patients improve quickly in hospitals or convalescent homes. Sedation is helpful, and administration of tranquilizers may give striking though partial relief in severe cases, when the patient is helpless. Huntington's chorea, or Huntington's disease, is a relatively rare, and invariably fatal, hereditary disease. The symptoms usually appear between ages 35 and 50 and worsen over time. They begin with occasional jerking or writhing movements or what appear to be minor problems with coordination. These choreiform movements worsen over the next few years and progress to random, uncontrollable, and often violent twitchings and jerks that merge with a person's more purposeful movements. Symptoms of mental deterioration may appear at some point, with apathy, lassitude, irritability, restlessness, or moodiness progressing to memory loss, dementia, manic depression, or schizophrenic symptoms. The choreiform muscular spasms, which are absent only during sleep, eventually become totally incapacitating. Death usually occurs 10 to 20 years after the appearance of the first symptoms. There is no effective therapy, though the choreiform movements may be partially and temporarily suppressed by phenothiazines or other antipsychotic drugs. The symptoms are caused by the gradual degeneration of neurons in the basal ganglia, a pair of nerve clusters deep within the brain that help control movement. The disease itself is passed on as an autosomal dominant trait, and the child of someone afflicted with it has a 50-percent chance of developing it. In 1983 a genetic test for detecting the disease was developed for use in research. In 1993 researchers determined that Huntington's chorea arises from an inherited mutation that produces extra copies of a gene sequence on chromosome 4; the resulting disruption of protein manufacture is apparently responsible for the death of nerve cells in the basal ganglia. Senile chorea is a progressive disease caused by vascular lesions. Onset usually occurs late in life. The muscular symptoms somewhat resemble those of Sydenham's chorea, and there may be a severe personality disturbance.