HD Blog

A neurologist will interview the individual intensively to obtain the medical history and rule out other conditions. A tool used by physicians to diagnose HD is to take the family history, sometimes called a pedigree or genealogy. It is extremely important for family members to be candid and truthful with a doctor who is taking a family history.

The doctor will also ask about recent intellectual or emotional problems, which may be indications of HD, and will test the person's hearing, eye movements, strength, coordination, involuntary movements (chorea), sensation, reflexes, balance, movement, and mental status, and will probably order a number of laboratory tests as well.

People with HD commonly have impairments in the way the eye follows or fixes on a moving target. Abnormalities of eye movements vary from person to person and differ, depending on the stage and duration of the illness.

The discovery of the HD gene in 1993 resulted in a direct genetic test to make or confirm a diagnosis of HD in an individual who is exhibiting HD-like symptoms. Using a blood sample, the genetic test analyzes DNA for the HD mutation by counting the number of repeats in the HD gene region. Individuals who do not have HD usually have 28 or fewer CAG repeats. Individuals with HD usually have 40 or more repeats. A small percentage of individuals, however, have a number of repeats that fall within a borderline region (see table 1).

The physician may ask the individual to undergo a brain imaging test. Computed tomography (CT) and magnetic resonance imaging (MRI) provide excellent images of brain structures with little if any discomfort. Those with HD may show shrinkage of some parts of the brain—particularly two areas known as the caudate nuclei and putamen—and enlargement of fluid-filled cavities within the brain called ventricles. These changes do not definitely indicate HD, however, because they can also occur in other disorders. In addition, a person can have early symptoms of HD and still have a normal CT scan. When used in conjunction with a family history and record of clinical symptoms, however, CT can be an important diagnostic tool.

Another technology for brain imaging includes positron emission tomography (PET,) which is important in HD research efforts but is not often needed for diagnosis.

Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892

NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.
Reviewed July 1, 2001