Tests and diagnosisBy Mayo Clinic staff
A diagnosis of Huntington's disease is based primarily on your answers to questions, a general physical exam, a review of your family medical history, and neurological and psychiatric examinations.
The neurologist will ask you questions and conduct relatively simple tests in the office to judge:
- Muscle strength
- Muscle tone
- Sense of touch
- Vision and eye movement
- Mental status
You'll likely be referred to a psychiatrist for an examination to judge a number of factors that could contribute to your diagnosis, including:
- Emotional state
- Patterns of behaviors
- Quality of judgment
- Coping skills
- Signs of disordered thinking
- Evidence of substance abuse
Brain imaging and function
Your doctor may order tests for assessing the structure or function of the brain. These may include:
- Brain-imaging tests. These images may reveal structural changes at particular sites in the brain affected by Huntington's disease, although these changes may not be apparent early in the course of the disease. These tests can also be used to rule out other conditions that may be causing symptoms. The imaging technologies may include MRI, which can produce detailed cross-sectional and 3-D images of the brain, or CT, which produces cross-sectional images.
- Electroencephalogram (EEG). Your doctor may order an EEG if you have experienced any seizures. The EEG uses a series of electrodes affixed to the scalp to record the electrical activity of the brain. Certain abnormal patterns in this activity may indicate problems likely to contribute to seizures.
Genetic counseling and testing
If symptoms strongly suggest a diagnosis of Huntington's disease, your doctor may recommend a genetic test for the defective gene. This test can confirm the diagnosis, and it may be valuable if there's no known family history of Huntington's disease or if no other family member's diagnosis was confirmed with a genetic test.
The test won't provide information that is beneficial in determining a treatment plan.
Before undergoing such a test, consider seeing a genetic counselor, who can explain the benefits and drawbacks of learning test results.
Predictive genetic test
A genetic test can be given to someone who has a family history of the disease but shows no signs or symptoms. This is called predictive testing. The test result has no treatment benefit, and it doesn't indicate when disease onset will begin or what symptoms are likely to appear first.
Some people may elect to do the test because they find it more stressful not knowing. Others may want to take the test before they make decisions about having children. Risks may include problems with insurability or future employment and the stresses of facing a fatal disease. These tests are only performed after consultation with a genetic counselor.
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