Classification of essential tremor.

Classification of essential tremor was attempted using tremor frequency; tremor duration; family history of tremor; responsiveness to alcohol, propranolol, and primidone; muscle contraction pattern; and long-latency reflexes. Sixty-one patients were evaluated. The majority of patients had a tremor frequency less than 7.0 Hz, a positive family history, and a positive response to alcohol. Approximately 46% of patients had a beneficial response with propranolol and 71% with primidone. Tremor frequency was inversely correlated with age and directly correlated with an antagonist pattern of muscle contraction. Enhanced long-latency reflexes were not found. Other characteristics of essential tremor were not significantly correlated. It is concluded that essential tremor can not be classified into subtypes.