Unilateral versus bilateral injections of botulinum toxin in patients with adductor spasmodic dysphonia

Both unilateral and bilateral thyroarytenoid muscle injections of Botox provide effective management of voice symptoms in patients with adductor spasmodic dysphonia; however, the preferred injection technique has not been established. In this study, 16 patients were treated with unilateral injections (72 injections total) and 33 patients were managed with bilateral injections (133 injections total). Individual assignments to injection type were based on treatment previously received and dose was adjusted according to the patient's previous treatment response. An optimal treatment included a benefit lasting 3 months or more with side effects lasting 2 weeks or less. Compared to patients receiving bilateral injections, those receiving unilateral injections more frequently noted a benefit of 3 months or more (p = 0.03), side effects of 2 weeks or less duration (p = 0.03), as well as both a 3-month benefit and a 2-week or less side effect (p = 0.0004). Injection type had no effect on optimal Botox dosing with repeat injections. Successive unilateral injections at the same dose were more likely (p = 0.012) than successive bilateral injections to produce the same or longer duration of benefit. We conclude that a unilateral injection routine has a more optimal and consistent treatment effect/side effect profile.