Post‐treatment clinical course following botulinum toxin injection therapy for adductor spasmodic dysphonia: Analysis of data from a placebo‐controlled, randomized, double‐blinded clinical trial in Japan

Objective Botulinum toxin (BT) therapy is a first‐line treatment for spasmodic dysphonia (SD). However, a detailed chronological course and clinical factors that affect the therapeutic effect have been vague. In this study, we analyzed the data from our placebo‐controlled, randomized, double‐blinded parallel‐group comparison/open‐label clinical trial of BT (Botox) to clarify these. Methods A total of 22 patients with abductor SD (ADSD) were enrolled. The female‐to‐male ratio was 20:2 with a mean age of 40.0 ± 10.3 years and a median duration of symptoms of 7.5 years. The therapeutic effect was evaluated based on the change in the number of aberrant morae (phonemes), GRBAS scale, Voice Handicap Index (VHI), and Visual Analogue Scale (VAS). Results The change in the number of aberrant morae peaked at 2 weeks and lasted for 12 weeks in the BT group with significance (P