Long-term therapy for spasmodic dysphonia: acoustic and aerodynamic outcomes

OBJECTIVE: To evaluate the long-term aerodynamic, acoustic, and electromyographic effects of serial botulinum toxin (BT) injections in patients with adductor spasmodic dysphonia. DESIGN: Two-year, nonrandomized, controlled, before-after study. SETTING: Ambulatory care clinic at a single academic medical center. PATIENTS: A convenience sample of 91 patients with adductor spasmodic dysphonia evaluated and treated during 2 years and 64 age- and sex-matched controls. INTERVENTIONS: Injections of BT into the thyroarytenoid muscles in conjunction with electromyographic evaluation and acoustic and aerodynamic evaluation before and after serial BT injections. MAIN OUTCOME MEASURES: Translaryngeal airflow, jitter, shimmer, signal-to-noise ratio, fundamental frequency, standard deviation of fundamental frequency, maximum phonation time, and inappropriate muscle activity by electromyography. RESULTS: Translaryngeal airflow, jitter, and shimmer improved significantly after serial BT treatments and showed sustained improvement over time. Fundamental frequency, standard deviation of fundamental frequency, and signal-to-noise ratio did not change significantly after BT treatment. Electromyographic data suggested decreased inappropriate muscle activity with repeated BT injections. CONCLUSION: Treatment with BT provides ongoing relief of voice perturbations in patients with adductor spasmodic dysphonia who undergo long-term cumulative therapy.