Double-blind controlled study of botulinum toxin in adductor spasmodic dysphonia.
The treatment of adductor spasmodic dysphonia using botulinum toxin A was conducted in 13 patients as a double-blind, placebo-controlled study. Patients were diagnosed independently by an interdisciplinary team consisting of speech pathologists, an otolaryngologist, and a neurologist. The toxin or saline was injected into each thyroarytenoid muscle under electromyographic and laryngoscopic guidance. Botulinum toxin A markedly reduced perturbation, decreased fundamental frequency range, and improved the spectrographic characteristics of the voice. Fundamental frequency and phonation time remained unchanged. Patients injected with botulinum toxin A noticed significant improvement in their voices in comparison with the placebo-treated group. Excessive breathiness of the voice occurred in two patients, and mild bleeding in one patient in the botulinum toxin A-treated group. Injection with saline resulted in edema of the vocal cord in one patient. Botulinum toxin A proved to be an effective and safe treatment of adductor spasmodic dysphonia.
The evidence from randomized controlled trials does not allow firm conclusions to be drawn about the effectiveness of botulinum toxin for all types of spasmodic dysphonia, or for patients with different behavioral or clinical characteristics.