Abstracts

RATIONALE: Left vagus nerve stimulation with the Cyberonics Vagal Nerve Stimulator (VNS) has been used in approximately 7000 patients world wide to treat intractable seizures, since 1988. Intermittent hoarseness has been reported as a frequent side effect. Persistent hoarseness occurred in a patient after implantation of the VNS. This study was designed to investigate acute and chronic changes and adaptations of the larynx due to long and short term stimulus. METHODS: Patients referred by the Epilepsy Management Program for implantation of the VNS were considered candidates for this study. After a complete head and neck interview and exam, patients underwent preoperative and postoperative video laryngostroboscopy. Patients were studied postoperatively during stimulation for 30 seconds at various mAmps strengths, 30 or 20 Hz signal frequency, and 500 or 250 msec pulse width. RESULTS: Four patients were studied. All had subjectively normal voices preoperatively and none reported trouble swallowing. One patient reported severe gastroesophageal reflux disease. All patients had normal laryngeal nerve function and normal vocal cord mucosal waves preoperatively. After implantation, all patients reported a noticeable intermittent difference in their voice. All patients reported being able to feel the effects of stimulation in their larynges. Two patients reported voice strain at times, which required modification of their voicing behaviors. One patient demonstrated medialization and paralysis of the vocal cord during stimulation causing a strained voice. The other three had lateralization of the stimulated vocal cord during stimulation with breathiness and compensation from the opposing cord. CONCLUSIONS: Vagus nerve stimulation for the treatment of intractable epilepsy is associated with hoarseness. Stimulation of the vagus nerve causes temporary paralysis of the ipsilateral vocal cord. While the effect does not seem to cause serious morbidity, it may require patients to modify their voice use in order to avoid strain and other laryngeal pathology.