Clinical Features of Essential Voice Tremor and Associations with Tremor Severity and Response to Octanoic Acid Treatment.

Abstract

The purpose of this study was to characterize the clinical features, tremor variability, and factors related to octanoic acid (OA) treatment response in essential voice tremor (EVT). Prospective, double blind, placebo-controlled, crossover study with secondary analysis. Clinical tremor features in 16 individuals with EVT were comprehensively assessed, and correlations with acoustic tremor severity were determined. Intrasubject and intersubject variability measures were analyzed from 18 repeated measures for each acoustic tremor variable. Clinical correlates of treatment response were evaluated, and cumulative effects over a 2-week period of OA drug dosing were assessed. Participants with EVT were 90% female with a mean age of 70.31 (±8.68) years at the time of testing. Neurologist-rated body tremor beyond the vocal tract region was present in 69% of participants, and multiple vocal tract regions contributed to the voice tremor. The mean frequency of amplitude tremor was 4.67 Hz (±0.88). Respiratory tremor was evident in 50% of participants. Participants experienced moderate voice-related disability as assessed on the Voice Handicap Index-10 (19.38, ±8.50), and increased speaking effort. Acoustic tremor severity was significantly associated with severity of tremor affecting vocal tract structures. Overall intrasubject consistency was strong (single measures intraclass correlation coefficient=0.701, P < .01), with high intersubject variability. Acoustic tremor severity was significantly, positively associated with treatment response, and results suggested a cumulative OA benefit for magnitude of amplitude tremor. This study identified common clinical correlates of EVT and demonstrated positive associations between acoustic tremor severity, severity of affected vocal tract structures, and response to treatment. 2 Laryngoscope, 131:E2792-E2801, 2021.