Nationwide survey of spasmodic dysphonia in Japan

Abstract

We conducted a nationwide survey of spasmodic dysphonia (SD) in Japan with the aim of revealing the epidemiological and clinical features of SD. Questionnaires were sent to 655 major otolaryngological institutions with a data disc which included representative voice samples of SD. We identified 1,534 patients over a period of 2 years. Among them, 887 (0.77 patient/100,000 population) were new patients. Prevalence of the disease in Japan was estimated to be 3.5-7.0 patients/100,000 population. The patients were predominantly 20-39 years in age (59.0%) and female in gender (1: 4.1 male/female ratio). Adductor type accounted for 93.2% of the patients. Clinical symptoms were characterized by strangled or effortful speech in the adductor type, and whispered or breathy voice quality in the abductor type. The median interval between the onset of symptoms and the first hospital visit was 3.0 years. Treatments by botulinum toxin injection into the intrinsic laryngeal muscles or type 2 thyroplasty were aggregately performed at several hospitals. This study suggested that SD is not yet fully recognized even among otolaryngologists and that diagnostic criteria and a standard therapeutic guideline need to be established.