Huntington's Disease is an inherited "autosomal dominant" disorder. This means each child of a
parent with H.D. 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.
These problems consist of 3 main groups of symptoms.
1) Motor Dysfunction
This is usually manifest by involuntary
movements. 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 be 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 People may become more withdrawn or isolated.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 the emotions. Some become uninhibited. 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 very 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 nerve cell survival mechanisms. The genetic defect has been identified, and can now be identified in a blood test to confirm the diagnosis (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 with which it kills nerve cells. Experimental studies are currently ongoing to attempt to stop Huntingtin's production or stop its effects on nerve cells.
There currently is no known treatment to
prevent or slow down the progression of Huntington's Disease. The currently available treatments are symptomatic. 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.
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.
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, Risrerdal, Olanzepine, Amantadine. Valproic acid can help myoclonic movements. Dopamine antagonists such as Trilafon (perphenazine) and Haldol 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
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 accommodation to a safe
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.