Relatives of Parkinson's patients have higher risk for action tremor

ST. PAUL, MN – Action tremor, the condition where goal-directed movements produce shaking in the moving body parts, most noticeably in the hands, is more apt to occur in first degree relatives of people with certain types of Parkinson's disease than in the population as a whole, according to a study published in the October 14 issue of Neurology, the scientific journal of the American Academy of Neurology.

Whether the tremor is a milder form of Parkinson's disease or whether it represents essential tremor, the most common neurological movement disorder, is unknown.

A team of researchers led by Elan Louis, MD, of the Neurological Institute in New York, studied the prevalence of action tremor among 5,563 relatives of patients with Parkinson's disease (487) and controls (409). The study was part of a larger study of the genetic epidemiology of Parkinson's disease, led by Karen Marder, MD, and supported by the National Institutes of Health and the Parkinson's Disease Foundation.

Action tremor occurred 2.1 times more often in the relatives of people with tremor-dominant Parkinson's disease (TD-PD), when compared with the relatives of the controls. Action tremor occurred 1.8 times more often among relatives of Parkinson's disease patients with postural instability gait disorder (PIGD-PD).

"Estimates of the risks of this condition in families of patients with Parkinson's disease gives us important insight into the genetic influence of PD," said Louis. "The strength of this study was that it was the first to ascertain the presence of action tremor in a large number of relatives and adjust the results for age and other factors."

Relatives of the Parkinson's disease patients in the study underwent a neurological examination for Parkinson's disease and essential tremor, and their medical histories were evaluated. Tests were adjusted for gender, education, race and whether they were alive or deceased.

The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as stroke, Alzheimer's disease, epilepsy, Parkinson's disease, autism and multiple sclerosis.

For more information about the American Academy of Neurology, visit its web site at http://www.aan.com.

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