Botox treatment in adductor spasmodic dysphonia: a meta-analysis.

Over the years many studies have been conducted to document the treatment effects of Botulinum toxin type A in adductor spasmodic dysphonia. The results of these studies have led to the view that overall Botulinum toxin treatment is moderately effective. This study reviews efficacy research qualitatively and quantitatively to determine the extent to which this conclusion is fully supported by the data. Although the data indicate moderate overall improvement as a result of Botulinum toxin treatment, they also suggest significant variation across patients, measurements, and treatment conditions. This result, together with methodological limitations and lack of standardization in BT efficacy research, justifies caution when making inferences regarding BT treatment benefit in adductor spasmodic dysphonia.