A COMPARISON OF BILATERAL AND UNILATERAL BOTULINUM TOXIN TREATMENTS FOR SPASMODIC DYSPHONIA

To assess the efficacy of bilateral or unilateral botulinum treatments for spasmodic dysphonia we injected botulinum toxin (type A) into the thyroarytenoid muscle of 24 patients with adductor type spasmodic dys phonia. Eleven patients underwent unilateral procedures and 13 bilater al procedures. Samples of sustained phonation were analyzed acoustical ly by a computer-assisted method and the air flow rates determined. Al l tests were conducted 1 week before injection and 1 week and 1 month after treatment. With unilateral injection, improvements in acoustic p arameters occurred as early as 1 week after treatment. With bilateral injections, only the voice break factor was significantly reduced afte r 1 week, while standard deviations of fundamental frequency, jitter, shimmer and signal-to-noise-ratios were reduced 1 month after treatmen t. In comparison with unilateral injections, the mean air flow rate wa s twice as high 1 week after bilateral injections, with no significant differences found 1 month after treatment. Clinically, both injection modes resulted in the reduction of laryngeal spasms as early as withi n 48 h after injection.