In Huntington disease, parts of the brain that help smooth and coordinate movements degenerate.
Movements become jerky and uncoordinated, and mental function, including self-control and memory, deteriorates.
Doctors base the diagnosis on symptoms, family history, imaging of the brain, and genetic testing.
Drugs can help relieve the symptoms, but the disorder is progressive, ultimately ending in death.
(See also Overview of Movement Disorders Overview of Movement Disorders Every body movement, from raising a hand to smiling, involves a complex interaction between the central nervous system (brain and spinal cord), nerves, and muscles. Damage to or malfunction... read more .)
Huntington disease affects 1 to 10 of 100,000 people. The number of people affected varies depending on which part of the world they live in. It affects both sexes equally.
The gene for Huntington disease is dominant Non–X-Linked (Autosomal) Inheritance Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are made of a very long strand... read more . That is, having only one copy of the abnormal gene, inherited from one parent, is sufficient to cause the disease. Therefore, children of a person who has Huntington disease have a 50% chance of developing it.
Huntington disease is caused by gradual degeneration of parts of the basal ganglia called the caudate nucleus and putamen. The basal ganglia are collections of nerve cells located at the base of the cerebrum, deep within the brain. They help smooth out and coordinate movements.
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 smooth out muscle movements, suppress involuntary movements, and coordinate changes in posture.
Symptoms of Huntington disease usually develop subtly, typically beginning between the ages of 35 and 40 but sometimes before adulthood.
During the early stages of Huntington disease, the face, trunk, and limbs may move involuntarily and rapidly. At first, people can blend these abnormal involuntary movements into purposeful ones so that the abnormal movements are barely noticeable. However, with time, the movements become more obvious.
Muscles may contract briefly and rapidly, causing the arms or another body part to suddenly jerk, sometimes several times in a row.
People may walk in a lilting or exaggeratedly jaunty way, like a puppet. They may grimace, flick the limbs, and blink more often. Movements become uncoordinated and slow. Eventually, the entire body is affected, making walking, sitting still, eating, speaking, swallowing, and dressing extremely difficult.
Mental changes frequently occur before or as the abnormal movements develop. These changes are subtle at first. People may gradually become irritable, excitable, and agitated. They may lose interest in their usual activities. They may be unable to control their impulses, losing their temper, having fits of despondency, or becoming promiscuous.
As Huntington disease progresses, people may behave irresponsibly and often wander aimlessly. Over years, they lose their memory and their ability to think rationally. They may become severely depressed and attempt suicide.
In advanced disease, dementia is severe, and people are confined to bed. Full-time assistance or nursing home care is needed. Death usually occurs 13 to 15 years after symptoms begin.
Huntington disease may be difficult to recognize in the early stages because symptoms are subtle. The disease may be suspected based on symptoms and a family history. Doctors should be told about relatives who have had mental problems or have been diagnosed as having a neurologic disorder (such as Parkinson disease Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more ) or a psychiatric disorder (such as schizophrenia Schizophrenia Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more ) because they may have had Huntington disease that was not diagnosed.
Computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI) is done to check for the degeneration of the basal ganglia and other areas of the brain usually affected by the disease and to rule out other disorders.
Genetic testing is done to confirm the diagnosis. Genetic testing and counseling are important for people who have a family history of the disease but no symptoms because people are likely to have children before symptoms appear. For such people, genetic counseling should precede genetic testing. They are referred to centers that have expertise in dealing with the complex ethical and psychologic issues involved.
As soon as possible after the diagnosis is made, people with Huntington disease should establish advance directives Advance Directives Health care advance directives are legal documents that communicate a person’s wishes about health care decisions in the event the person becomes incapable of making health care decisions. There... read more , indicating what kind of medical care they want at the end of life.
No cure exists for Huntington disease. However, certain drugs, including antipsychotic drugs Antipsychotic drugs Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more (such as chlorpromazine, haloperidol, risperidone, and olanzapine) may help control the agitation. Drugs that reduce the amount of dopamine (such as tetrabenazine, deutetrabenazine, and the antihypertensive reserpine), can help stop (suppress) the abnormal movements..
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Genetics Home Reference: What is Huntington disease? This web site describes Huntington disease and discusses what causes it and how it is inherited, as well as provides links to its diagnosis and treatment.