Meta-analysis of botulinum toxin treatment of spasmodic dysphonia: a review of 22 studies.

This meta-analysis focuses on the treatment effects of the use of botulinum toxin in laryngeal dystonia. The vocal symptoms are characterized by spasms of the laryngeal muscles thus the use of the term spasmodic dysphonia (SD). The objective of the intervention, i.e. botulinum toxin treatment, is to reduce or eliminate the vocal spasms and thus improve the acoustic regularity of the voice. The purpose of the present study was to assess the efficacy of botulinum toxin in the treatment of SD by engaging in a 'best synthesis' systematic summary of existing research. The average treated SD patient in the 22 studies subjected to meta-analysis obtained 97% improvement as a result of treatment with botulinum toxin.