Botulinum Toxin Therapy for Spasmodic Dysphonia in Japan: The History and an Update

Abstract

Spasmodic dysphonia (SD) is a rare neurological disorder that impairs phonatory function by triggering involuntary and intermittent contractions of the intrinsic laryngeal muscles. SD is classified into three types: adductor SD (AdSD), abductor SD (AbSD), and mixed SD. Of these, AdSD accounts for 90–95% of disease; younger females are predominantly affected. Botulinum toxin injection into the laryngeal muscles is safe, minimally invasive, and very effective. Here, we review the history of clinical research for SD conducted in Japan. The first use of botulinum toxin injection therapy to treat SD in Japan was by Kobayashi et al. in 1989. The group developed an objective mora (syllable) method to evaluate SD severity. Recently, we conducted a placebo-controlled, randomized, double-blinded clinical trial of botulinum toxin therapy for AdSD and an open-label trial for AbSD to obtain the approval of such therapy by the Japanese medical insurance system. The mora method revealed significant voice improvement and the evidence was of high quality. Additionally, a clinical trial of type 2 thyroplasty using titanium bridges confirmed the efficacy and safety of such therapy. These studies broadened the SD treatment options and have significantly benefited patients.

Guidelines for the Use of Botulinum Toxin in Otolaryngology From the Korean Society of Laryngology, Phoniatrics and Logopedics Guideline Task Force

“…1984 Laryngeal injection of BT to treat spasmodic dysphonia was first performed by Blitzer et al Thereafter, hundreds of articles were published; most reporting it to be effective [1]. 1990 The American Academy of Neurology and the American Academy of Ophthalmology and Otolaryngology suggested that BT could be safely and effectively used for various hyperkinetic diseases.…”

Comparison of the efficacy and adverse effects of unilateral or bilateral botulinum toxin injections for adductor spasmodic dysphonia: a systematic review and meta-analysis

“…SD can be further classified based on the affected muscle groups as either adductor spasmodic dysphonia (ADSD), abductor spasmodic dysphonia (ABSD), or mixed-type dysphonia, with ADSD being the most common subtype (accounting for 90–95% of cases) [ 4 ]. The irregular voice breaks caused by laryngeal muscle spasms have been shown to significantly impair patient quality of life, leading to decreased work attendance and performance [ 5 , 6 ].…”

The Effect of Pyridostigmine as an Antidote for Botulinum Type A: An Experimental Study on Rabbits

“…These neurotoxins act on the peripheral nervous system, where they inhibit the release of acetylcholine (ACh) from the synaptic terminal of neuromuscular junctions. 15,16 Currently, BoNT type A injections are a popular non-surgical and non-invasive treatment to optimize and change an individual's facial appearance and achieve rejuvenation. 17 In this study, we aimed to demonstrate the efficacy of anticholinesterase inhibitor pyridostigmine in accelerating spontaneous recovery following botulinum toxin injections in a rabbit model.…”