Clinical characteristics of essential tremor: data from a community-based study.

BACKGROUND

99.5% of individuals with essential tremor (ET) who live in the community have mild tremor and do not attend clinics. Clinic-based studies of ET have not allowed investigators to characterize the full clinical spectrum of this disorder. In community-based studies of ET, the primary focus has been the prevalence rather than the clinical characteristics of ET.

OBJECTIVE

To describe the clinical characteristics of ET as seen in a community-based study.

METHODS

73 subjects with ET, identified in a community-based study of ET in Washington Heights-Inwood, New York, underwent a standardized 84-item physician-administered tremor interview and a 26-item videotaped tremor examination which included 12 bedside tests for ET. Two neurologists who specialized in movement disorders and who demonstrated excellent interrater agreement rated the severity of tremor using a 0 to +3 clinical rating scale and assigned a total tremor score (range, 0-36) and a diagnosis of ET.

RESULTS

Diagnoses in the 73 cases were: definite ET (18, 24.7%), probable ET (32, 43.8%), and possible ET (23, 31.5%). The mean total tremor score was 17.8 of 36. Thirty-six of 73 (49.3%) were asymptomatic, answering "no" to the question "do you often have shaking or tremor that you can't control?" Sixty-seven of 73 (91.8%) had not been prescribed medication for tremor. On average, subjects received tremor ratings of > or =+2 on only 5.4 of the 12 bedside tests for ET. Kinetic tremor was rated as more severe than postural tremor in 72 (98.6%) of 73 cases.

CONCLUSIONS

We present the clinical findings of a group of largely untreated, unselected cases of ET that would not otherwise have come to neurologic attention. The tremor was mild, often asymptomatic, and not uniformly present throughout the examination. It was rarely treated. The kinetic component of the tremor was more severe than the postural component. These clinical data further our understanding of the clinical spectrum of ET.