Essential tremor: clinical, electromyographical and pharmacological studies in 146 Chinese patients.

From February 1984 to February 1988, 258 cases of various kinds of tremor were seen in our movement disorder clinic. Among them, 146 cases (57%) were diagnosed as essential tremor, and of these, 96 (65.8%) were males and 50 (34.2%) were females, ranging in age from 14 to 89 years (mean: 36 years). The main tremor occurred in the hands (100%), and in a few cases were combined with head, leg, lip, voice and neck tremors. A familial tendency was obvious in 47 cases (32%). The surface electromyographic (EMG) study of essential tremor revealed two patterns, one of synchronous type (73%) and the other of alternating type (27%). Its frequency was between 5 and 9Hz. The burst duration was short (50-100 msec) and the amplitude was low (less than 200 mu v). All cases were divided into two groups to received propranolol therapy, 78 cases with high dosages (120-240 mg/day) and 68 with low dosages (60-80 mg/day). The higher dose was better in effect than the lower one (p less than 0.01). Propranolol also had effect on tremors of alternating type (p less than 0.01), which is different from previous reports.