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.