The swallowing side effects of botulinum toxin type A injection in spasmodic dysphonia

Botulinum toxin type A (BOTOX) injection of the thyroarytenoid muscle is used to control speech symptoms in patients with adductor spasmodic dysphonia. Transient difficulty in swallowing liquids is a common treatment side effect. Laryngeal movement durations were measured during swallowing in 13 adductor spasmodic dysphonia patients undergoing treatment and in 6 normal control subjects in order to determine the following: 1. whether, prior to the injection, laryngeal movement durations were longer in the spasmodic dysphonia patients than in the control subjects; 2. whether movement durations increased following the injections; 3. whether preinjection swallowing difficulties related to postinjection swallowing measurements and postinjection patient reports of swallowing problems. A piezoelectric movement transducer was shown to be accurate for noninvasive measurement of laryngeal movement duration in relation to muscle onset and offset for hyoid elevation and relaxation. Before botulinum toxin type A injection, no significant differences in swallowing duration were found between the patient and control groups. Four patients with swallowing complaints prior to injection had longer laryngeal movement durations than the other spasmodic dysphonia patients and the control subjects. Following injection, laryngeal movement durations increased in the patients with spasmodic dysphonia, and eight patients reported dysphagia for an average of 2 weeks. Relationships were found between the patients' initial reports of swallowing problems and increased laryngeal movement durations before and after botulinum toxin type A injection. Those patients initially reporting swallowing difficulties had severe dysphagia for 2 weeks after the injection. Patient reports of dysphagia prior to injection may indicate a greater likelihood of significant dysphagia following thyroarytenoid injection with botulinum toxin type A.