Difference of disability between electrophysiologic subgroups of essential tremor.

Abstract

The aim of the study was to test the validity of the controversial subdivision of essential tremor (ET) patients into electrophysiological subgroups. We evaluated a hundred patients with ET using surface electromyographic (EMG) recordings of antagonists forearm muscles and distinguished three groups: the first group showed synchronous activity of antagonistic muscles, the second showed alternating activity of antagonist muscles; and the third group consisted of patients whose EMG recordings were not compatible with the other two groups. We compared patients with synchronous and alternating activity in terms of sex, age at onset, duration of illness, family history of tremor, symmetry and frequency of tremor, and the scores of a disability scale. The only significant difference between the patients with synchronous and alternating activity was that the patients with synchronous activity were more disabled. This result adds to the evidence for distinct electrophysiological subgroups of ET with distinct clinical properties.