Background: Spasmodic dysphonia (SD) is a focal dystonia and adductor SD is the most common form. The standard treatment for adductor SD is EMG-guided, transcutaneous injections of botulinum toxin into the thyroarytenoid muscle.

Objective: Report the clinical presentation of SD, treatment with botulinum toxin injection, injection technique, results, and adverse effects.

Material and Method: A reviewed of clinical records of patients diagnosed with SD at the Voice Clinic between April 1999 and December 2004 at Srinagarind Hospital, Khon Kaen University, Thailand. Thirtyseven patients were identified but only twenty-five were treated with EMG-guided botulinum toxin injection to the thyroarytenoid muscle

Results: In the presented 37 patients, SD was more common in women (89%) than men (11%). The median duration of symptoms prior to diagnosis was 12 months: all were the adductor type. The average age at onset was 46 years. The presenting symptoms included influence to the voice (84%), hoarseness (70%), strained or strangled voice (65%), decreased loudness (27%), and breathy voice (22%). A vocal tremor coexisted with dystonia in 60% of the presented patients. Treatment with botulinum toxin injection was carried out on 25 patients for 78 injections (mean, 3 per patient). The time for botulinum toxin to take effect averaged 2.3 days (peak effect, 7 days). The patients received substantial relief from their SD symptoms, an average functional improvement of 39.2% (37.6% initially vs. 76.8% finally). Patients’ best voice was achieved within one week and persisted for an average of 13.6 weeks. Side effects from the injections included mild breathiness (68%) and mild choking on fluid (56%). After injection, decreased potential for volume was a common complaint, but since all of the patients experienced increased fluency, they were satisfied. Almost all of the patients returned for repeat injections when the benefit diminished.

Conclusion: Botulinum toxin therapy has become the standard care for the treatment of SD. An acceptable and flexible treatment plan to produce a balance between decreased spasms and loss of function must be developed for each patient.

Keywords: Botulinum toxin, Spasmodic dysphonia