Huntingdon Disease
Q: A psychiatrist referred a patient to me to help confirm his suspicions that his 35-year-old male patient suffered from Huntington disease. This patient had a family history of the disorder; his father, a brother, and an uncle were all diagnosed with it. Upon examination, the patient was found to be “moody,” with involuntary jerky and choreic movements, including facial grimacing, hesitant speech, and wide gait. Would you suggest an imaging study or genetic testing? Which method is more reliable, and which is the most cost-effective?
A: The diagnosis of Huntington disease is suggested by the history and neurologic examination and is confirmed by a CAG repeat sequence genetic test. A positive test consists of more than 30 trinucleotide repeats of the CAG test. It is important not to abuse this test by studying patients in whom the clinical diagnosis is in doubt or in families who understand the implications of the test and do not want to undergo the study. A positive study does not predict with accuracy the time of onset of symptoms or the severity of the disease, although longer repeat lengths tend to correlate with earlier onset and more malicious disease. In general, the larger the number of trinucleotide repeats, the earlier the disease becomes manifest. Currently, there is no particularly effective treatment for Huntington disease, so the physician and the patient must consider the implications of a positive study. Be sure to also consider a genetic counseling group when deciding whether to order a genetic test.
Thalmic Syndrome
Q: I have a 65-year-old female patient who had a stroke with left-sided hemiparesis about 1 year ago. She is now able to ambulate with a cane but complains of severe shooting pains and a sensation of “heat” on her left side from the top of her head to the sole of her foot, which occurs daily. What could be the explanation for this? What treatment would you recommend?
A: If the stroke involved the thalamus or parietal lobe, she may have a form of thalamic syndrome (Dejerine-Roussy disease). Treat her with a tricyclic antidepressant.
Epilepsy and the Peripheral Nervous System
Q: Is there any theory that certain kinds of epilepsy are generated at the peripheral nerve level that then radiates to the brain, causing electric shock to the brain and resulting in unexplained symptoms in a patient along with normal EEG test results?
A: Some do believe that certain central nervous system phenomena could be triggered by activity in the peripheral nervous system, but there is no good evidence that epilepsy is caused in this way. The mechanism of vagal nerve stimulation as an anti-epileptic treatment is unknown, but, of course, the fact that it works does not prove that epilepsy can be caused by something arising in the periphery.
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