Huntington Disease: Summary and Overview

Huntington disease (HD) is an inherited brain disorder that causes cells in specific parts of the brain to die. The first thorough description of the disease was by New York physician George Huntington in 1872.  He described a disease, which was then known as chorea or choreia, a borrowed Latin word that derives from the Greek khoreia, a choral dance (like choreography). The term comes from the involuntary twisting, turning, writhing and dancing movements that are characteristic of the disease. The HD gene is dominant, which means that each child born to a parent with Huntington disease has a 50% chance of sharing the same fate.

Currently, there are no treatments that will slow down or stop the disease in humans. The disease leads to complete incapacitation and, eventually, death. But hope for a meaningful treatment has increased as we understand more and do more research into Huntington Disease.

Huntington Disease: Causes

Huntington disease is caused by a hereditary defect in a single gene. The HD gene is dominant, which means that a person needs only one copy of the defective gene to develop the disorder.

A person inherits two copies of every gene (other than the sex chromosomes) — one copy from each parent. A parent with a defective Huntington gene could pass on either the healthy copy or the defective one. If a parent has Huntington’s, each child in the family has a 50 percent chance of having the disease.

Huntington disease causes the programmed cell death of the brain’s neurons. Since neurons undergo a programmed degeneration, Huntington’s has a broad impact on a person’s cognitive and motor abilities, and usually results in movement, psychiatric and cognitive disorders. About 1 in 10,000 people have Huntington Disease. The incidence occurs in males and females equally.

Huntington Disease: Symptoms

Most people develop Huntington Disease in their ‘40s and ‘50s, but it could happen either later or earlier. If it happens before the age of 20, the disease is called juvenile Huntington Disease. The symptoms are slightly different and they progress faster and vary slightly. The variant is classified as juvenile, akinetic-rigid or Westphal variant HD.

Huntington Disease affects the neurons of the brain, which means that motor and cognitive skills are affected and lose function as the disease progresses.

Motor symptoms include:

• Muscle rigidity
• loss of coordination
• Loss of balance
• Jerky and involuntary movements
• Difficulty talking
• Impaired gait and posture
• Difficulty walking, as the disease progresses

Cognitive impact includes:

• Difficulty planning and prioritizing
• Lack of flexibility and getting stuck in a thought
• Lack of impulse control
• Memory loss
• Difficulty in making decisions
• Spatial awareness so getting lost more often
• Difficulty in finding the right words
• Concentration difficulties

With the condition, changes in intellectual functioning are often one of the first symptoms to appear. People with Huntington disease unlearn many of their skills that they have known for years. They may find it hard to drive, remember things, answer questions, and make decisions. Changes in handwriting have also been observed as Huntington disease progresses. They may forget family members and have difficulty talking, walking, and learning new things.

The most common psychiatric disorder associated with Huntington’s Disease is depression. This isn’t just the patient’s reaction to the progressing condition, but because the disease destroys neurons, injuring the brain, and triggering depression. It can also lead to other psychiatric disorders such as insomnia, obsessive compulsive disorder, irritability, anxiety, mania, reduced sex drive, fatigue, feelings of worthlessness and guilt, and suicidal thoughts.

Huntington Disease: Diagnostic Tests

Your doctor will likely give you a physical exam, ask you a series of psychological questions, view your family history, test your motor neuron skills.

Medical imaging, such as computerized tomography (CT) and magnetic resonance imaging (MRI), shows the visible cerebral atrophy that occurs in the advanced stages of the disease. For an earlier diagnosis, functional neuroimaging techniques such as fMRI and PET can show changes in brain activity before the onset of physical symptoms. A positive result is not considered a diagnosis, since it may be obtained decades before the symptoms begin. However, a negative test means that the individual does not carry the expanded copy of the gene and will not develop Huntington Disease.

Huntington Disease: Treatment Options

Currently, there is no cure for Huntington disease. Treatment is a matter of managing its symptoms. There are medications to help control the chorea and involuntary movements, such as Tetrabenazine (Xenazine) and haloperidol (Haldol) and clozapine (Clozaril).

There are also drugs to help control the psychiatric illnesses associated with the disease, e.g. anti-depressants to control depression, such as escitalopram (Lexapro), fluoxetine (Prozac, Sarafem) and sertraline (Zoloft).

Persons may work with psychotherapist, psychiatrist, psychologist or clinical social worker to help them develop coping strategies, manage expectations during the progression of the disease for the patient and their families who must try to make the best of the changes. 

Physical therapy sessions have proven to be very effective in helping people adjust and improve the motor neuron skills they need to perform activities of daily living.

According to a study by the California-based Salk Institute for Biological Studies, fisetin, a natural compound found in strawberries and other fruits and vegetables, may slow down the progress of the disease. The benefits are more likely in the early stages of the disease although more research is needed on its impact overall. 

Huntington Disease: Prevention

Since Huntington disease is hereditary, there is no real way to prevent it from occurring. Persons with a family history of the disease may consider genetic testing especially if they want to have children. However, as there is no cure it is advisable to make sure the results are discussed with a genetic counselor in case of a positive result, which will indicate that the person will develop the disease.

Huntington Disease: Conclusion

Huntington disease is genetic, degenerative condition. It causes the programmed death of the neurons of the brain. It leads to a loss of motor and cognitive function and psychiatric disorders. While there is no cure, today there are a number of medications, treatments and therapies to manage the condition

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