Huntington’s Disease is an inherited “autosomal dominant” disorder. This means each child of a parent with Huntington’s disease has a 50% chance of inheriting the disease. It is a progressive neurologic illness that results in problems that typically start between age 30 and 55, though with each successive generation, the disorder will appear earlier and often more severely.
The problems which patients with Huntington’s disease present with consist of 3 main groups of symptoms:
1 – Motor Dysfunction
This is usually characterized by involuntary movements, called “chorea“. Early on, these may be very minor twitches, of outstretched fingers, or fleeting movements of the muscles of facial expression. Over time these movements slowly become more dramatic and start to interfere with normal coordination. People will complain of increasing clumsiness, muscle jerking, dropping things, slurred speech and swallowing difficulties. This can unfortunately progress to a degree where the affected individual becomes dependent on others for care. This collection of symptoms does not occur in all cases, with some developing stiffness and slowing of movement. The latter pattern is called the “Westphal Variant” and is more common in young onset cases.
2 – Emotional Symptoms
This can precede, coincide with, or follow the onset of the movement disorder. The changes may be very subtle, early on in the illness, but can progress and become more severe. There may be depression, manic behavior, irritability, loss of insight, and judgment. People may become more withdrawn or isolated. There may be an inability to control one’s emotions. Some become disinhibited in their behaviour, resulting in a loss of control of baser impulses. There is a increased risk of suicide if these problems are not identified and treated.
3 – Cognitive Dysfunction
Memory problems can precede, coincide with, or follow the onset of the movement disorder. Like the other features of Huntington’s, this comes on slowly, with perhaps just a minor reduction in concentration initially. Over time the problems increase. There is a slowing of thought, loss of attentiveness, and decision making becomes more difficult. Complicated tasks (multitasking) become no longer possible, or lead to increasing stress. Calculation abilities start to fail. Memory for recent events becomes increasingly impaired. Affected people may eventually need help to manage their personal affairs.
The disorder progresses differently from one individual to the next. Typically within an average of 10 years of onset of symptoms, affected individuals will be dependent on others for care.
The cause is known to be an inherited defect resulting in a failure of brain cell survival mechanisms. The genetic defect has been identified, and can now be identified in a blood test to confirm the diagnosis (via DNA analysis). The abnormal gene results in the excess production of a protein that has been labeled “Huntingtin“. Researchers have identified this protein and are now identifying the mechanism by which it kills brain cells. Experimental studies are currently ongoing to attempt to stop Huntingtin’s production or stop its effects on brain cells.
There is currently no known treatment to prevent or slow down the progression of Huntington’s disease. The currently available treatments help to control symptoms. There are medications that can help reduce the involuntary movements, and control the psychiatric manifestations of the illness. No medication has yet proven to improve memory or cognitive function, but many studies are ongoing.
A variety of medications can be used to help settle the movement disorder. Treatment needs to proceed with caution. Frequently, treatment settles chorea but the functional status of the patient is worsened. Medications that can settle the chorea include; Tetrabenazine, risperidone, olanzapine, amantadine. Valproic acid can help myoclonic movements. Dopamine antagonists such as Trilafon (perphenazine) and Haldol (haloperidol) are recommended only for severe cases in which the previously mentioned medications fail.
There are effective treatments for the majority of the personality changes that can occur (depression, sleep disorders, anxiety etc.). Psychoactive drugs of a variety of types may be useful depending on the type of psychosocial problems encountered.
Unfortunately there is no available treatment for the memory disorder seen with this condition, and adjustments in the patient’s life must be made, as required, including the provision of additional care or changing accommodations to a safer environment to assist in their ability to cope despite these changes.
Planning for the future, and caregiver assistance is of extreme importance in the management of this condition. A multi-disciplinary approach involving Allied Health Care team members, such as occupational therapists (OT), speech and language language pathologists (SLP) and social worker play a key role in the care of a person with Huntington’s disease.
As this illness runs in families there are many implications regarding being tested to find out if you have the gene even prior to symptoms developing. This testing is available but should be offered only with a genetic consultation to determine if there are any expected risks when providing this information. Testing in individuals under age 18 without symptoms is not offered in Canada.