Huntington's Chorea
What is Huntington's chorea?
Huntington's disease (HD) is an inherited disorder in which a mutated gene causes nerve cells (neurons) in certain parts of the brain to degenerate. This disease can be devastating, impairing a person's ability to think, feel and move. HD is a chronic, progressive disease, which means that it gets worse over time until it eventually causes death. There is no cure for HD.
The disease is also called Huntington's chorea, in reference to the involuntary, jerking movements. These movements are often described as dance-like (“chorea” comes from the Greek word for dance). In addition to characteristic movement problems, HD also results in emotional problems and dementia. About 30,000 people in the United States have HD, according to the National Institutes of Health.
Huntington's chorea is the result of neuron death in various parts of the brain. Neurons are vital for all aspects of body function. Some neurons (called sensory neurons) transmit information from the sensory organs to the brain. Others (called motor neurons) carry information from the brain and spinal cord to the muscles and glands around the body. Still others (interneurons) are responsible for reflex actions. Special chemicals called neurotransmitters help neurons to transmit their signals back and forth from the brain.
The genetic mutation that results in Huntington's chorea causes the body to produce too much of various neurotransmitters. Excess levels of these neurotransmitters leads to the death of neurons in certain parts of the brain, with the basal ganglia (an area located deep in the brain) typically affected first. The basal ganglia is one of the parts of the brain associated with motor function, as well as aspects of emotions and learning. In particular, the neurons of the striatum (the area of the basal ganglia that controls movement and balance) are affected, although the cerebral cortex (area of the brain responsible for mental function, sensation and movement) is also affected.
Though the age of onset varies, every person who has inherited the mutated gene responsible for Huntington's disease will develop the disease at some point in life. The most common form of Huntington's chorea develops during middle-age and is referred to as adult-onset HD. In some cases, HD develops before a patient turns 20 and has been diagnosed in children as young as age 2. This form of Huntington's disease is known as juvenile HD. Children with HD may have slow, stiff movements that mimic Parkinson's disease instead of the typical jerking movements. In many cases, it results in death within 10 years.
It is much less common for people over the age of 55 to develop HD. A condition called senile chorea occurs in elderly patients and is characterized by symptoms similar to HD. However, senile chorea is primarily a movement disorder and is typically not accompanied by the dementia and emotional problems experienced by people with HD. Senile chorea is not caused by the same gene mutation that causes Huntington's disease.
The rate of HD progression varies from patient to patient. The duration of the illness may range between 10 and 30 years. It is generally observed that the earlier the disease develops, the faster it progresses. Over time, patients usually become more physically and mentally disabled. There is no cure for the disease and, despite advances in medications used to treat the symptoms, many patients eventually require long-term care in a nursing home.
Huntington's chorea continues to progress until it eventually results in a patient's death. Common causes of death include infection and injuries related to falls caused by the movement problems
How is it diagnosed?
A physician may suspect Huntington's disease (HD) in patients who develop movement disorders in addition to behavioral problems and dementia. Because of the slow progression rate of the disease in some people, HD may be diagnosed after several years of the initial onset of the disease. If Huntington's disease is suspected, the patient may be referred to a neurologist.
In diagnosing Huntington's chorea, a physician will perform a complete physical examination. Patients may undergo a neurological examination. During these examinations, several aspects of the patient's health may be tested, including:
- Balance
- Coordination
- Eye movements
- Hearing
- Mental status
- Movement
- Vision
In some cases, especially if there is no family history of HD, the physician may recommend a genetic test in order to look for the mutated gene in the patient's DNA. For a genetic test, a physician takes a sample of the patient's blood to identify whether the mutated gene is present.
Imaging tests, such as computed axial tomography (CAT) scans and magnetic resonance imaging (MRI) are sometimes used to rule out other conditions and support a diagnosis of HD.
Some people with a family history of HD may wish to undergo pre-symptomatic testing in order to determine whether they will develop the disease. This may involve a neurological examination and genetic test to look for signs and symptoms of the disease. Genetic counseling is also a recommended component of pre-symptomatic testing. Genetic counselors are people who are trained in aspects of genetics and are able to discuss the implications of genetic test results with patients. This may be especially helpful for couples with a family history of HD who are contemplating having a child.Depression is common; suicide is a risk, while intellectual function is still intact. The person might develop delusions or a frank psychosis.
How is Huntington's chorea treated?
There is no cure for Huntington’s disease (HD) and the progression of the disease cannot be slowed down or halted. Generally, treatment for Huntington's chorea is aimed at reducing the patient’s symptoms and maintaining a good quality of life for as long as possible.
Several medications are available to help control symptoms related to HD. For example, dopamine blockers and depletors and antidyskinetics may be used to treat and control movement problems. Additionally, antidepressants and tranquilizers can help reduce emotional symptoms such as mood swings and depression. Other symptoms, such as delusions, hallucinations and psychosis may be treated using antipsychotic drugs.
Although these drugs are effective for many patients, most of them cause several side effects, including fatigue, hyperexcitability and restlessness.
There are also several self-care measures that patients can take to help reduce their symptoms. For example HD patients who remain physically active are less prone to falls and other consequences of their movement problems. Patients may also benefit from speech therapy and other forms of therapy (e.g., occupational or physical therapy) that can help them deal with the symptoms of their illness.
Proper nutrition is an important part of coping with Huntington's chorea. People with HD may burn as many as 5,000 calories in a day because of their excess movements. This may result in malnourishment and dehydration in some patients. People with HD should ensure that they get adequate nutrition to maintain their body weight and drink plenty of fluids to reduce the risk of dehydration. Additionally, eating is often complicated for HD patients because they may have trouble swallowing. Occupational therapists can also help teach patients how to improve their swallowing technique.
Finally, many patients with Huntington’s disease experience emotional difficulties, both as a symptom of the disease and as a result of living with HD. Sessions with a therapist or participation in a support group can help make this aspect of the disease more manageable.
Medications
Pamelor (Nortriptyline), Prozac (Fluoxetine), Zyprexa (Olanzapine), Klonopin (Clonazepam), Geodon (Ziprasidone), Symmetrel (Amantadine)
Predicted outcome
The prognosis is poor. Most individuals become unable to care for themselves and require institutionalization at the end stage of the disease. Death usually comes after ten to twenty years from pneumonia or heart failure.
Alternatives
Other possibilities are benign familial chorea, a stroke involving the basal ganglia, and Wilson's disease.
Appropriate specialists
Neurologist, physiatrist, psychiatrist, and medical geneticist.
Last updated 11 July 2015