An evaluation of laryngeal muscle activation in patients with voice tremor.

Eight patients with voice tremor were studied to characterize laryngeal muscle involvement. Electromyographic (EMG) recordings were made from intrinsic laryngeal muscles, simultaneously with some extrinsic laryngeal muscles, respiratory movement, and voice recordings during respiration, whisper, and phonation. Spectral measures were used to determine the tremor frequency and the prominence of spectral peaks in the EMG, respiratory and acoustic signals, while correlation coefficients were computed between pairs of tremulous EMG signals to measure the synchrony of tremor between muscles. The intrinsic laryngeal muscles were tremulous during respiration and speech, with the thyroarytenoid most often involved. Tremor was also detected in some of the extrinsic muscle recordings and the percentage of muscles with tremor was higher during phonation than during whisper or respiration. Time delays were found between tremor oscillations in laryngeal muscles. Because the thyroarytenoid was affected in all the patients studied, botulinum toxin injections may be beneficial in treatment of this voice disorder.