Effects of type II thyroplasty on adductor spasmodic dysphonia

Abstract

Objectives: Type II thyroplasty, or laryngeal framework surgery, is based on the hypothesis that the effect of adductor spasmodic dysphonia (AdSD) on the voice is due to excessively tight closure of the glottis, hampering phonation. Most of the previous, partially effective treatments have aimed to relieve this tight closure, including recurrent laryngeal nerve section or avulsion, extirpation of the adductor muscle, and botulinum toxin injection, which is currently the most popular. The aim of this study was to assess the effects of type II thyroplasty on aerodynamic and acoustic findings in patients with AdSD. Study Design: Case series. Setting: University hospital. Subjects and Methods: Ten patients with AdSD underwent type II thyroplasty between August 2006 and December 2008. Aerodynamic and acoustic analyses were performed prior to and six months after surgery. Mean flow rates (MFRs) and voice efficiency were evaluated with a phonation analyzer. Jitter, shimmer, the harmonics-to-noise ratio (HNR), standard deviation of the fundamental frequency (SDF0), and degree of voice breaks (DVB) were measured from each subject's longest sustained phonation sample of the vowel /a/. Results: Voice efficiency improved significantly after surgery. No significant difference was found in the MFRs between before and after surgery. Jitter, shimmer, HNR, SDF0, and DVB improved significantly after surgery. Conclusions: Treatment of AdSD with type II thyroplasty significantly improved aerodynamic and acoustic findings. The results of this study suggest that type II thyroplasty provides relief from voice strangulation in patients with AdSD.