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---------------------------------------------------------------------- Gene Region Linked to Tremor ---------------------------------------------------------------------- NEW YORK (Reuters) -- For the first time, researchers have identified a gene region that increases susceptibility to essential tremor, a chronic shaking of the head, arms, neck and voice that is most commonly found in people over age 40. The finding is the first step in locating the gene that causes the disorder, which is thought to be inherited 96% of the time. The researchers examined a large American family of Czech descent that had 18 members out of 67 with essential tremor, according to a report in the journal Movement Disorders. The family was also suffering from "genetic anticipation" in which each generation tended to develop the first signs of tremor earlier than the previous generation. In this case, the average age of onset was 63 in one generation, 29 in the next and age 11 in the youngest family members. The researchers found that a gene region located on chromosome 2, called 2p22-p25, was more common in those with the tremor than those without it. "This finding suggests that a single highly penetrant gene is sufficient to cause at least one form of essential tremor in a single large family," reported lead author Dr. Joseph J. Higgins, of the Clinical Neurogenetics Unit at the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland. The study also suggests that essential tremor is caused by factors other than those that cause tremors in Parkinson's disease or other diseases, which have been linked to gene regions on chromosomes 4 and 9. About 1% to 6% of people over age 40 have essential tremor while 0.4% of people over 40 have Parkinson's disease, a condition in which tremors are caused by a progressive nerve cell degeneration. Essential tremor usually worsens when a person is performing a task, but is minimal or disappears at rest. In comparison, those with Parkinson's disease usually have a "resting tremor," or shaking at rest. There is no cure for essential tremor. Certain drugs, and in drastic cases, surgery may help control the tremor, though these treatments are only partly successful and can have severe side effects. More research is needed to determine the specific gene on chromosome 2 that causes the fine shaking seen in those with essential tremor disorder, the authors noted. "Several genes have been identified in the chromosome 2p22-p25 region, but none appears to be an evident essential tremor gene candidate by function or pattern of expression," they concluded. "Further studies in other families with essential tremor will help identify the gene(s) responsible for this common disabling condition and increase our understanding of human motor control." By Theresa Tamkins SOURCE: Movement Disorders (1997;12:859-864) [ 1997, Reuters Health eLine] <http://www.medscape.com/reuters/tue/t1110-2f.html> --------------------------------------------------------------------- janet [log in to unmask]