A comparison of the efficacy of unilateral versus bilateral botulinum toxin injections in the treatment of adductor spasmodic dysphonia.

The current treatment of choice of adductor spasmodic dysphonia due to focal dystonia is thyroarytenoid-vocalis injection of botulinum toxin type A (Botox). Botox exerts its effect by presynaptic motor endplate blockade, preventing the release of acetylcholine and causing muscle paresis. Botox treatment protocols vary. Some centres perform unilateral injections, whereas others treat both cords. Our hypothesis is that unilateral injections may reduce the severity of whisper voice and aspiration side effects in the early two to three weeks after treatment. The purpose of this study, therefore, is to compare the efficacy of unilateral versus bilateral Botox injections in the treatment of adductor spasmodic dysphonia in terms of duration of effect versus the side effects of breathing and swallowing difficulties. This study presents data from a retrospective chart review and a prospective telephone interview of all patients receiving bilateral and unilateral Botox injections.