Prevalence of asymptomatic tremor in relatives of patients with essential tremor
E. D. Louis, B. Ford and S. L. Pullman
Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
BACKGROUND: The extent to which essential tremor (ET) clusters within
families (ie, the familial aggregation of ET) is not precisely known. In
part, this is because studies assign disease status in relatives of
patients with ET based solely on interviews without conducting physical
examinations. This may lead to underascertainment of affected relatives
with mild asymptomatic ET. OBJECTIVE: To determine the prevalence of
asymptomatic ET among relatives of patients with ET. METHODS: Interview and
examination of 25 patients with ET and 58 of their relatives. The interview
included 12 questions that screened the patients for ET. Two neurologists
who specialize in movement disorders reviewed the videotaped examinations.
Based on standardized criteria, diagnoses included ET (definite, probable,
or possible) on normal. RESULTS: Of the 8 relatives who received diagnoses
of ET, 5 (62.5%) had asymptomatic ET. Hence, 5 (8.6%) of the 58 relatives
(95% confidence interval 1.4%-15.8%) had asymptomatic ET. In those with
asymptomatic ET, there was a preponderance of young individuals with mild
tremor in the nondominant hand. CONCLUSIONS: The prevalence of asymptomatic
ET in relatives of patients with ET was similar to that of symptomatic ET.
Family studies that do not perform both an interview and a physical
examination will underascertain the number of affected relatives.
Therefore, future family studies should evaluate relatives of patients with
ET with an interview supplemented by a physical examination.
