A preliminary 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
The neurologist may also perform standardized tests to assess:
- Mental agility
- Language function
- Spatial reasoning
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 brain-imaging tests for assessing the structure or function of the brain. The imaging technologies may include magnetic resonance imaging (MRI) or computerised tomography (CT) scans that provide detailed images of brain structures.
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.
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. But the test won't provide information that might help determinine a treatment plan.
Before undergoing such a test, the genetic counselor will explain the benefits and drawbacks of learning test results. The genetic counselor can also answer questions about the inheritance patterns of Huntington's disease.
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. In principle, federal laws exist that make it illegal to use genetic testing information to discriminate against people with genetic diseases.
These tests are only performed after consultation with a genetic counselor.