A study by Porta et. al (2004), showed that the injection of Botulinum toxin Type A (2.5 IU BTX-A (BOTOX; Allergan)) in both vocal cords of Tourette patients improved the vocal tics in 93% of the patients after the tretment, with 50% of them being tic-free. The mean response time was 5.8 days, while the mean duration of response reached up to 102 days. A side effect of the treatment however, was hypophonia (experienced by 80% of the patients). Hypophonia refers to soft speech often resulting from lack of vocal muscle coordination.
