Spasmodic Dysphonia

Abstract

Spasmodic dysphonia (SD) is a chronic voice disorder characterized by excessive or inappropriate contraction of laryngeal muscles during speech. SD manifests as excessive glottic closure (adductor type) or sudden opening of the vocal folds (abductor type). Strained or strangled voice is the main symptom of adductor type SD, while abductor type SD presents with a breathy or absent voice. Adductor type SD accounts for 97% of all SD cases and 70% display abnormal contractions of extra laryngeal muscles. SD is currently understood to be a focal dystonia of inner laryngeal muscle during speech. Injection of botulinum toxin into laryngeal muscles is the primary treatment for SD, similar to other dystonia diseases. As the effects of botulinum toxin last for around three months, patients need repeated injections. There are two kind of surgical procedures which aim to achieve permanent emission, namely type 2 thyroplasty (TP2) and bilateral thyroarytenoid muscle myectomy (TAM). Both of these are effective and over 50% of patients can become symptom-free. However, in some cases, patient voices can become breathy and pitch ranges are reduced. For abductor type SD, there are no effective treatments apart from botulinum toxin injections into posterior cricoarytenoid muscles which open the vocal folds.