Prospective study of patients' subjective responses to botulinum toxin injection for spasmodic dysphonia.

Adductor spasmodic dysphonia (SD) is a speech disorder resulting from involuntary contractions of the laryngeal muscles. Botulinum toxin (BT) injection of the thyroarytenoid muscle is an effective, though temporary, treatment for most SD patients. Though there are reports of objective improvements in voice quality, there are no large studies of patients' subjective responses to treatment over time. In the present study, patients were given voice diaries to rate vocal spasms, hoarseness, breathiness, volume problems, and dysphagia before and the after treatment. Analysis of these diaries revealed that: (1) most side effects had resolved 4 to 6 weeks after injection, whereas vocal spasm relief persisted; (2) vocal spasm relief and severity of side effects peaked within 1 week; and (3) unilateral injections, though as effective in relieving vocal spasms, caused less volume and swallowing problems than did bilateral injections.