Effects of Botulinum Toxin Type A Injections on Aerodynamic Measures of Spasmodic Dysphonia

The effects of botulinum toxin type A (BOTOX®) injections on aerodynamic measures of phonation were examined in 30 patients with adductor spasmodic dysphonia. Patients received bilateral injections of 2.5 U of botulinum toxin type A in each thyroarytenoid muscle. Measures of air pressure, average airflow, coefficient of variation (CV) of airflow, and laryngeal resistance were obtained before the injections and at 2 and 10 weeks after the injections. These measures were also obtained from 12 normal subjects. Compared with normal subjects, the spasmodic dysphonia patients had significantly higher preinjection values for air pressure, CV of airflow, and laryngeal resistance. At 2 and 10 weeks after the botulinum toxin type A injections, the spasmodic dysphonia patients showed a significant increase in the average airflow values and a significant decrease in the CV of airflow values and the laryngeal resistance values. At 10 weeks after the injections, the values for the three measures began to approach the preinjection values. It is concluded that these aerodynamic measures of phonation can provide useful measures of treatment outcome in adductor spasmodic dysphonia.