Spasmodic Dysphonia: Botulinum Toxin Injection after Recurrent Nerve Surgery

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Abstract
The purpose of this study was to determine if botulinum toxin injections into the thyroarytenoid muscle would reduce symptoms in adductor spasmodic dysphonic patients who had experienced symptom recurrence after recurrent laryngeal nerve surgery. Five patients were seen between 3 to 10 years after surgery with a return of speech symptoms and persistent unilateral vocal fold paralysis. Before injection, comparisons with controls on spectrographic measures of pitch and voice breaks, aperiodicity, and sentence length demonstrated significant symptoms of spasmodic dysphonia (p ≤ 0.02). Electromyographic measures demonstrated equal levels of thyroarytenoid muscle activation on the operated and non‐operated sides with bipolar needle electrodes, and heightened activity in both muscles relative to normal. Therefore, symptom return was associated with thyroarytenoid innervation after recurrent nerve surgery. In all patients, the thyroarytenoid muscle on the side operated on was injected with type A botulinum toxin. In two patients, toxin was also injected on the side not operated on. Significant (p ≤ 0.002) reductions in all speech symptoms occurred after injection. Electromyographic measures demonstrated significant reductions in the percent activation levels of both the injected muscle and noninjected muscles (p ≤ 0.01). Botulinum toxin injections were an effective treatment of post‐surgical symptom recurrence in adductor spasmodic dysphonia.