Recent Advances in Botulinum Toxin Injections for Neurological Laryngeal Diseases

Botulinum toxin (BoNT) injection has become an important treatment modality for neurological disorders of the larynx. It is particularly effective in treating laryngeal dystonia (formerly known as spasmodic dysphonia). The efficacy of BoNT injection depends on accurate intramuscular injection and appropriate dose setting, and various injection techniques have been developed. Electromyography-guided injection has been considered the standard method, but recently, various methods such as point-touch technique, endoscopy-guided, and ultrasound-guided injections have been attempted. The injection dose also has a significant impact on the therapeutic effect and the occurrence of side effects, so individualized dose adjustment is necessary according to the patient’s condition and treatment response. Bilateral injection is more effective than unilateral injection in adductor laryngeal dystonia in terms of duration of effect, but the possibility of side effects is also higher. In abductor laryngeal dystonia, BoNT is injected into the posterior cricoarytenoid muscle, and careful dose determination is required considering the risk of airway obstruction. For laryngeal tremor, thyroarytenoid muscle injection alone or simultaneous injection of strap muscles can be considered based on recent findings. BoNT injection has limitations in that repeated treatments are required, some patients may have limited efficacy, and resistance may develop due to antibody formation.