The effect of vagal nerve stimulation on voice.

OBJECTIVE: Vagal nerve stimulation therapy through implanted vagal nerve stimulators is an accepted therapy for refractory seizure disorders. One significant side effect of vagal nerve stimulation is voice change. This study evaluates the impact that these voice changes have on patients' lives, and the physiological effects that vagal nerve stimulation has on the larynx.
METHODS: Patients were selected from the pool of patients at Rush-Presbyterian-St. Luke's Medical Center who underwent implantation of vagal nerve stimulator devices. Three methods were used to evaluate the impact the devices had on patients and on their vocal cords. First, a questionnaire was sent to the patients to ascertain the degree of vocal and social impairment that occurs as a result of the implant. Second, videostroboscopy was used to analyze the effect that vagal nerve stimulation had on the larynx. Third, computerized voice analysis objectively analyzed the patients' voices both during and in between vagal nerve stimulations.
RESULTS: Although patients noted significant voice changes during stimulation of the implant, the impairment is well tolerated and less debilitating than the underlying seizure disorder. Hyperstimulation of the affected vocal cord was observed during vagal stimulation with paramedian positioning, vocal fold tensing, and loss of mucosal wave. Increase in jitter and shimmer was consistent.
CONCLUSION: Vagal nerve implantation devices create significant but well-tolerated vocal side effects. Investigation of these devices increases our understanding of laryngeal physiology and may give insight into future laryngeal pacing. Preimplantation laryngeal examination should be performed routinely to rule out laryngeal pathology that could lead to significant complications.