Chorea refers to brief, repetitive, jerky, or dancelike uncontrolled movements caused by muscle contractions that occur as symptoms of several different disorders. The English word "chorea" itself comes from the Greek word choreia, which means "dance." The symptom takes its name from the rapid involuntary jerking or twitching movements of the patient's face, limbs, and upper body.
A patient with chorea may appear restless, fidgety, or unable to sit still. The body movements are continually changing and may appear to move from one part of the
Other symptoms that may occur together with chorea include athetosis, which refers to slow, sinuous, writhing movements of the hands and feet, and ballismus, which refers to violent flinging or flailing of the limbs. A patient with one of these symptoms in addition to chorea may be said to have choreoathetosis or choreoballismus.
In some cases, only one side of the patient's body is affected by the involuntary movements. This condition is known as hemichorea.
Causes and associated disorders
The basic cause of choreic movements is overactivity of a neurotransmitter called dopamine in a set of structures deep within the brain known as the basal ganglia. The basal ganglia belong to a larger part of the nervous system that controls the muscles responsible for normal movement.
Several different unrelated disorders and conditions may lead to imbalances of dopamine in the basal ganglia, including:
- Huntington's chorea (HC), an incurable hereditary disorder caused by a mutation in a gene on the short arm of human chromosome 4. It is characterized by dementia and psychiatric disturbances as well as chorea.
- Sydenham's chorea, a treatable complication of rheumatic fever following a streptococcal throat infection. It occurs most often in children and adolescents.
- Chorea gravidarum or chorea occurring in the first three months of pregnancy. It is most likely to affect women who had rheumatic fever or Sydenham's chorea in childhood.
- Senile chorea, which is gradual in onset, is not associated with other causes of chorea, does not cause personality changes, and develops in people over the age of 60. At one time, senile chorea was thought to be a late-onset form of HC, but is presently considered to be the result of a different genetic mutation.
- Blockage or rupture of one of the arteries supplying the basal ganglia.
- Metabolic disorders. About 2% of patients with abnormally high levels of thyroid hormone (hyperthyroidism) develop chorea. Abnormally low levels of calcium (hypocalcemia) may also produce chorea.
- Infectious diseases that affect the central nervous system. Chorea may be a symptom of viral encephalitis or late-stage neurosyphilis.
- Medications. Some drugs, most commonly those used to treat psychotic disorders or Parkinson's disease, cause chorea as a side effect. Other drugs that sometimes cause chorea include anticonvulsants (antiepileptic drugs), lithium, amphetamines, and some antinausea medications.
A doctor diagnosing the cause of chorea is guided by such factors as the patient's age and sex as well as medication history and family history. A patient with symptoms of Huntington's chorea is typically an adult over 35, whereas Sydenham's chorea most often occurs in children aged six to 14. Huntington's chorea affects both sexes equally, whereas Sydenham's chorea affects girls twice as often as boys. A patient with a family history of Huntington's can be given a blood test to detect the presence of the gene that causes HC. A history of a recent throat infection or rheumatic fever suggests Sydenham's chorea. Metabolic disorders can be detected by blood tests.
Hemichorea or chorea accompanied by ballismus may indicate a vascular disorder affecting the basal ganglia, particularly when the chorea is sudden in onset. The doctor will order imaging studies, usually computed tomography (CT) scans or magnetic resonance imaging (MRI) if an arterial blockage or rupture is suspected. Neurosyphilis and encephalitis are diagnosed by testing a sample of the patient's cerebrospinal fluid.
In general, chorea is not treated by itself unless the movements are so severe as to cause embarrassment or risk injury to the patient. Drugs that are given to treat chorea suppress the activity of dopamine in the basal ganglia but may also produce such undesirable side effects as muscular rigidity or drowsiness. These drugs cannot be given to women with chorea gravidarum because they may harm the fetus; pregnant patients may be given a mild benzodiazepine tranquilizer instead. Drugs given to treat patients with HD may help to control chorea, but cannot stop the progression of the disease.
The prognosis of chorea depends on its cause. Huntington's chorea is incurable, leading to the patient's death 10–25 years after the first symptoms appear. Almost all children with Sydenham's chorea, however, recover completely within one to six months. Chorea gravidarum usually resolves by itself when the baby is born or shortly afterward. Chorea caused by a vascular disorder may last for six to eight weeks after the blockage or rupture is treated. Chorea associated with metabolic disorders usually goes away when the chemical or hormonal imbalance is corrected.
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Rebecca Frey, PhD