Effects of adductor muscle stimulation on speech in abductor spasmodic dysphonia

OBJECTIVE: To determine whether adductor laryngeal muscle stimulation might be a beneficial treatment alternative for abductor spasmodic dysphonia (ABSD). STUDY DESIGN: Baseline comparisons were made on measures of voiceless consonant and syllable duration between patients with ABSD and normal control subjects, and speech and voice production with and without muscle stimulation were compared within 10 patients with ABSD. METHODS: Baseline group comparisons were conducted on measures of syllable and voiceless consonant duration between the patients and the control subjects. Neuromuscular stimulation was applied to the thyroarytenoid or lateral cricoarytenoid muscles in the patients during extended phonation, and measures were made of fundamental frequency and sound pressure level in the stimulated and nonstimulated conditions. Voiceless consonant duration was compared with and without adductor laryngeal muscle stimulation during syllable repetitions and sentences in the patients. RESULTS: Before stimulation, the patients had increased syllable durations in comparison with control subjects (P = .003). Repeated within-patient comparisons with and without stimulation demonstrated significant (P < .008) reductions in voiceless consonant durations during syllable repetition. The more severely affected patients had the greatest reductions in voiceless consonant duration during sentence production. CONCLUSIONS: Adductor muscle stimulation improved speech production in patients with ABSD, and the improvement was greatest in the most severely affected patients. Therefore adductor muscle stimulation has potential for benefiting patients with ABSD.