Botulinum toxin injections for the treatment of spasmodic dysphonia

Botulinum toxin is currently the gold standard of treatment for patients with spasmodic dysphonia. It has been used over the past two decades to treat both adductor and abductor forms of the disorder. The results of this review of randomized controlled trials indicate that botulinum toxin is effective for some aspects of voice production, including perceptual measures of improvement post-injection, variability of fundamental frequency, vocal intensity and subglottal air pressure. These benefits may be dependent on certain subject variables, such as the amount of voice use immediately post-injection and treatment variables such as dosage and location of injection. These results should currently be interpreted with caution, however, as studies have used small sample sizes and have methodological differences which prevent between-study comparisons.