Clinical Application of Botulinum Toxin to Functional Dysphonia

Functional dysphonia (FD) is a disease entity which includes various voice disorders in the absence of structural or neurologic laryngeal pathology. Muscle tension dysphonia (MTD), psychogenic dysphonia are representative FD with completely different pathogenesis. Therefore there is no standard treatment modality for FD, the first step of treatment of FD is differentiating patient's voice symptoms from other organic voice disorders and other functional voice problems. MTD is a functional voice disorder caused by hyperfunction of intrinsic and extrinsic laryngeal musculature. Symptoms include increased vocal effort, roughness, fatigue and odynophonia. First line for MTD is indirect or direct voice therapy. Unfortunately, many patients with MTD improve with voice therapy alone. For these patients, various modalities tried; lidocaine application, surgical excision of the false vocal folds, and botulinum toxin injection, etc. Botulinum toxin injections are widely used in the field of otolaryngology, especially for spasmodic dysphonia. However, its use in FD or MTD has only been described in few case reports. The aim of this lecture is to evaluate the feasibility of botulinum toxin injection for FD, especially MTD.

Comparison of botulinum toxin and propranolol for essential and dystonic vocal tremors

OBJECTIVES: Vocal tremors, which cause social difficulties for patients, may be classified as resting or action tremors. Of the vocal action tremors, essential and dystonic tremors are the most common. Botulinum toxin and oral medications have been used to treat vocal tremors, but no comparative clinical trials have been performed. The aim of this study was to compare the effects of botulinum toxin injection and the oral administration of propranolol in the treatment of essential and dystonic vocal tremors. METHODS: This clinical trial recruited 15 patients, divided into essential and dystonic vocal tremor groups. Patients in both groups received successive treatment with botulinum toxin and propranolol. The treatments were administered at different times; the order of treatment was randomly selected. Patients were assessed with flexible nasofibrolaryngoscopy and with perceptual and acoustic voice evaluations. A statistical significance level of 0.05 (5%) was used. RESULTS: Botulinum toxin produced statistically significant improvements in perceptual measures of vocal instability in patients with dystonic vocal tremors compared with baseline values and treatment with propranolol. The acoustic measure of variability in the fundamental frequency was significantly lower in patients with dystonic vocal tremors after treatment with botulinum toxin. CONCLUSION: Essential and dystonic vocal tremors responded differently to treatment. Dystonic vocal tremors responded significantly to treatment with botulinum toxin but not oral propranolol. Essential vocal tremors did not respond significantly to either treatment, perhaps due to the small number of patients, which is a limitation of this research.