Chorea

Definition

Chorea refers to a range of involuntary movements that arise as a feature of several different disorders or conditions. It is a disorder of the nervous system, and one of a group of disorders called hyperkinetic disorders. This term draws attention to the fact that in chorea there is excessive movement, called choreic movements.

Choreic movements result from muscle contractions mainly in the hands, forearms, lower legs, face and sometimes the chest. These uncontrollable movements are rapid and jerky, occurring with irregular and unpredictable timing. These movements often differ from those found in the normal repertoire of movements and so, apart from being abrupt and purposeless, they may also have an abnormal appearance. Choreic movements tend to flow from one part of the body to adjacent parts, giving the impression of dancing. In fact, the term chorea is derived from the Greek word meaning “to dance”.

Chorea usually affects both sides of the body, but in some instances only one side of the body is involved. This is referred to as hemichorea.

Choreic movements in the face include frowning, raising the eyebrows, pursing the lips and smiling. Grimacing, which usually takes the form of caricatures of normal facial expressions, also occurs. The muscles of the jaw and tongue may be involved, and involuntary movements of these can impair chewing and swallowing.

Sometimes muscles in the chest and diaphragm are affected, which can cause jerky and irregular breathing. This may be accompanied by abnormal respiratory sounds such as grunts and gasps. Speech may also be impaired, becoming slurred, erratic or explosive, due to the effects on the muscles used in breathing as well as from involuntary tongue movements.

Choreic movements disrupt voluntary movement, so people with chorea may appear clumsy and sometimes walk with a wide, swaying or lurching gait.

Chorea often occurs together with athetosis, a condition characterised by slow, writhing movements of the limbs. When this occurs, the combined set of movements is referred to as choreoathetosis.

In severe cases of chorea, movements sometimes occur as a violent flinging of the limbs which results in severe, uncontrollable flailing. These are called ballistic movements, and this condition is known as ballism or choreoballism. Ballistic movements can be severely debilitating and even lead to injury.

Choreic movements disappear during sleep.

Causes

A set of structures in the brain, called the basal ganglia, form an integral part of a larger system that controls the muscles responsible for bodily movements. Dopamine, a neurotransmitter, plays an important role in the functioning of the basal ganglia. (Neurotransmitters are chemicals that control transmission of nerve impulses between nerve cells.)

A number of disorders cause dopamine to become overactive in nerve pathways within the basal ganglia, and this, in turn, causes choreic movements.

Who gets it and who is at risk?

Chorea is common in some very rare diseases, and is a rare occurrence in some more common conditions or disorders. A few of the better-known conditions are:

Huntington’s Disease

Huntington’s Disease, also known as Huntington’s Chorea, is one of the most common causes of chorea. It is a progressive neurological disease which, aside from chorea, also causes personality changes and dementia.

Huntington’s Disease is a genetic disorder caused by a single defective gene. There is a 50% chance that a carrier will pass the gene on to his or her children. It is virtually 100% certain that carriers will get the disease. There is wide variation in the age of onset of the disease, ranging from childhood to old age, but the average age of onset is 40. Since most cases manifest only in middle age, the disease is often passed to children before the parent is aware of being a carrier.

Sydenham’s Chorea

Rheumatic fever is a childhood disease caused by a reaction to a Streptococcal bacterial infection, which primarily affects the heart. It occurs most commonly in children between the ages of six and 14 years, is rare after puberty, and almost never manifests after the age of 20. Chorea occurs as a symptom in approximately 20% of cases of acute rheumatic fever. Choreic movements may arise during an attack of rheumatic fever, or they may occur days, weeks or even months afterwards.

When chorea occurs in association with rheumatic fever, it is called Sydenham’s Chorea, also referred to as chorea minor, acute chorea or rheumatic chorea. Originally, this condition was called St. Vitus’ Dance.

Girls are twice as likely as boys to get Sydenham’s Chorea.

Pregnancy

Rarely, chorea may manifest during pregnancy. When it does so, it is referred to as chorea gravidarum. Symptoms usually appear in the first three months of pregnancy. Chorea is more likely to affect women who have had Sydenham’s Chorea in childhood, and is more likely to occur in first pregnancies.

Vascular Disease

The term vascular accident is used to refer to either the blockage or the rupture of an artery. Chorea is sometimes caused by a vascular accident in one of the arteries that supply blood to the basal ganglia. The structures become starved of oxygen, which impairs their functioning and can lead to chorea.

Vascular disease greatly increases the risk of vascular accidents.

Hyperthyroidism

Hyperthyroidism is a condition that results from abnormally high levels of thyroid hormone. Common symptoms are rapid heartbeat, palpitations, nervousness and increased sweating. Chorea manifests as a symptom in about 2% of cases of hyperthyroidism, and occurs most commonly between ages 20 and 40.

Senile Chorea

Occasionally, chorea may occur in people over 60 years old who have no underlying illness that might cause chorea. This is referred to as senile chorea. The symptoms usually develop gradually, but do not become as severe as they do in Huntington’s Disease.

Drugs and chorea

A number of medical drugs cause chorea as a side effect. When chorea emerges as a result of drug use, it is referred to as tardive chorea or tardive dyskinesia.

Medical drugs that most commonly cause tardive chorea include:

• many of the drugs used in the treatment of psychotic conditions such as schizophrenia
• certain antidepressant medications
• some medications that alleviate nausea

Although it is very rare, some women develop chorea in response to the use of oral contraceptives.

Diagnosis

Chorea itself is diagnosed on the basis of observation of its characteristic movements. Once chorea has been recognised however, it is important for a diagnosis to be made of the underlying condition that is the cause of the chorea. Diagnosis of some of these conditions is discussed below.

Diagnosis of Huntington’s Disease

As this is a hereditary disease, family history plays a very important role in the diagnosis of Huntington’s Disease. If a person develops chorea, and one of their parents or grandparents has or had Huntington’s Disease, it is extremely likely that they too will have Huntington’s disease.

A specific blood test can detect the presence of the gene that causes Huntington’s Disease, and make a definitive diagnosis of the disease. The test can also be used to discover whether individuals with a family history of the disease, but who have no symptoms yet, have inherited the gene that causes the disease.

Diagnosis of Sydenham’s Chorea

The occurrence of chorea in childhood usually suggests a diagnosis of Sydenham’s Chorea. This diagnosis can be confirmed by means of a blood test for rheumatic fever. Sometimes however, chorea occurs some time after a child has had rheumatic fever, in which case the blood test might not be useful in diagnosis.

Diagnosis of vascular accident as a cause of chorea

Chorea caused by a vascular accident usually begins abruptly and often assumes the extreme form of hemiballismus. This describes a movement disorder characterised by violent flinging motions in the arm. Furthermore, choreic movements resulting from a vascular accident are often confined to one side of the body. When chorea shows these features, a vascular origin is strongly suggested.

Modern technologies, such as computed tomography and magnetic resonance imaging, can reveal detailed images of the brain. These images allow sites of vascular accident in the brain to be identified, and can therefore confirm a suspected vascular cause of chorea.

Diagnosis of hyperthyroidism

Hyperthyroidism is diagnosed by means of a blood test.

Treatment

The most appropriate way to treat chorea is to treat the underlying condition causing the chorea. However, treatment of the underlying condition is not always possible (as in the case of Huntington’s Disease, an incurable genetic disorder), and such treatment does not always lead to an immediate cessation of chorea.

Drugs are nevertheless available to treat the symptoms of chorea, whatever the underlying cause might be. Most of these drugs work by suppressing the activity of dopamine. Unfortunately, these drugs often have severe side effects, such as sedation and muscular rigidity. For this reason, drugs are seldom used in mild cases of chorea that do not cause significant embarrassment or disability.

Treatment with drugs is usually successful in cases where unpleasant side-effects do not occur. In many instances however, the side effects of the drugs prove to be debilitating or intolerable. In these cases, low drug dosages have to be used, achieving only partial suppression of symptoms.

When chorea occurs in pregnancy, dopamine-suppressing drugs cannot be used because of potentially harmful effects on the foetus.

Outcome

With Huntington’s Disease, onset of symptoms is usually gradual, but the disease progresses relentlessly and eventually causes full-blown chorea and profound dementia. Huntington’s Disease is therefore severely disabling and ultimately fatal. The duration of the illness ranges from 10 to 25 years.

Typically, symptoms of Sydenham’s Chorea appear abruptly, worsen gradually over a period of two to four weeks, and then slowly begin to subside. On average, it takes about three months for symptoms to completely disappear. In about 25% of cases however, signs of chorea may wax and wane for a year or more.

If chorea appears in pregnancy, the symptoms usually resolve spontaneously by the time of delivery or shortly thereafter.

Chorea is often severe when caused by a vascular accident, but symptoms generally subside within about six to eight weeks.

When to see the doctor

If you start to develop any of the symptoms discussed here, you should consult your doctor.

Reviewed by Prof. Don du Toit, University of Stellenbosch