Chorea, Athetosis, and Hemiballismus
Chorea and athetosis are usually symptoms of another disorder, although chorea may develop on its own in older people or in pregnant women.
Chorea and athetosis can occur together, usually causing writhing, dancelike movements.
Hemiballismus affects a limb (the arm more often than the leg) on one side of the body, causing it to fling wildly.
For chorea and athetosis, treating the cause may help, as may antipsychotic drugs.
(See also Overview of Movement Disorders.)
Chorea and athetosis, which may occur together as choreoathetosis, are not disorders. Rather, they are symptoms that can result from several very different disorders.
Chorea and athetosis result from overactivity in the basal ganglia, the part of the brain that helps initiate and smooth out and coordinate intended (voluntary) movements initiated by nerve impulses from the brain. In most forms of chorea, an excess of dopamine, the main neurotransmitter used in the basal ganglia, prevents the basal ganglia from functioning normally. Drugs and disorders that increase dopamine levels or increase the sensitivity of nerve cells to dopamine tend to worsen chorea and athetosis.
Locating the Basal Ganglia
The basal ganglia are collections of nerve cells located deep within the brain. They include the following:
The basal ganglia help initiate and smooth out voluntary muscle movements, suppress involuntary movements, and coordinate changes in posture.
Chorea and athetosis occur in Huntington disease, a hereditary degenerative disorder.
Chorea may also occur in the following:
Sydenham chorea (also called St. Vitus’ dance or Sydenham disease), a complication of rheumatic fever (a childhood infection caused by certain streptococci) that is characterized by jerky, uncontrollable movements and that can last for several months
Overactivity of the thyroid gland (hyperthyroidism)
A high blood sugar level (hyperglycemia)
A low level of parathyroid hormone (hypoparathyroidism)
A tumor or stroke affecting a part of the basal ganglia called the caudate nucleus
Paraneoplastic syndromes (symptoms caused by hormones produced by the tumor or by antibodies produced by the immune system in response to the tumor)
Pregnancy, causing a condition called chorea gravidarum that occurs during the first 3 months of pregnancy but disappears without treatment shortly after women give birth
Rarely, use of oral contraceptives
In a few people, antipsychotic drugs can cause a chorea called tardive dyskinesia (characterized, for example, by puckering of the lips and tongue or by choreoathetosis).
Chorea sometimes develops in older people for no apparent reason. This chorea, called senile chorea, tends to affect the muscles in and around the mouth. However, if such movements develop, people should see a doctor.
Hemiballismus is usually caused by a stroke that affects a small area just below the basal ganglia called the subthalamic nucleus. The subthalamic nucleus helps control voluntary movements.
Chorea typically involves the hands, feet, and face. The nose may wrinkle, the eyes may continually flit, and the mouth or tongue may continually move. The movements are not rhythmic, but they seem to flow from one muscle to the next and may seem dancelike. The movements may merge imperceptibly into purposeful or semipurposeful acts, sometimes making the chorea hard to identify.
Athetosis usually affects the hands and feet. The slow writhing movements often alternate with holding parts of the limbs in certain positions (postures) to produce a continuous, flowing stream of movement.
When chorea and athetosis occur together, the movements are writhing, dancelike, and slower than in chorea but faster than in athetosis.
Hemiballismus affects one side of the body. The arm is affected more often than the leg. Hemiballismus may be temporarily disabling because when a person tries to move the limb, it may fling out uncontrollably.
The diagnosis of chorea, athetosis, or hemiballismus is based on symptoms and observation by a doctor. The doctor also asks which drugs a person is taking to check for drugs that may be causing the symptoms.
Tests may be done to identify the cause. These tests may include
Chorea in people who have hyperthyroidism or hyperglycemia usually lessens when that disorder is treated. Sydenham chorea and chorea caused by a stroke often gradually subside without treatment. If chorea is caused by a drug, stopping the drug may help, but the chorea does not always disappear.
If pregnant women have severe chorea, they may be treated with barbiturates during the pregnancy. However, after delivery, chorea lessens and eventually disappears on its own.
If people have chorea and athetosis, treatments that help relieve the chorea tend to also help relieve athetosis.
Drugs that block dopamine’s action may help control the abnormal movements. These drugs include antipsychotic drugs, such as fluphenazine, haloperidol, and risperidone. Drugs that reduce the amount of dopamine released, such as reserpine, deutetrabenazine, and tetrabenazine, may also help. However, improvement may be limited.
Hemiballismus usually goes away on its own after several days, but it sometimes lasts for 6 to 8 weeks. Antipsychotic drugs may help suppress hemiballismus. If drugs are ineffective, deep brain stimulation may be used. For this procedure, tiny electrodes are surgically implanted in the basal ganglia. The electrodes send small amounts of electricity to the specific area of the basal ganglia thought to be responsible for hemiballismus and can thus help lessen symptoms.