Chorea consists of repetitive, brief, jerky, large-scale, dancing-like, uncontrolled movements that start in one part of the body and move abruptly, unpredictably, and often continuously to another.

Athetosis is a continuous stream of slow, sinuous, writhing movements, generally of the hands and feet. Chorea and athetosis can occur together (choreoathetosis).

Chorea and athetosis aren't diseases; rather they are symptoms that can result from several very different diseases. People with chorea and athetosis have abnormalities in the basal ganglia of the brain. (see page 279 in Chapter 59, Biology of the Nervous System)

The basal ganglia's job is to smooth out the coarse movements that are initiated by commands from the brain. In most forms of chorea, an excess of the neurotransmitter dopamine in the basal ganglia disrupts its fine-tuning function.

Drugs and illnesses that alter dopamine levels or the brain's ability to recognize dopamine can make chorea worse.

The disease that most often produces chorea and athetosis is Huntington's disease, but it is fairly rare, affecting fewer than 1 in 10,000 people.

Treatment

Chorea that develops as a drug's side effect may improve if the drug is stopped, but the chorea doesn't always disappear. Drugs that block dopamine's action, such as antipsychotic drugs, may help control the abnormal movements.