Abstracts

Vagus nerve stimulation (VNS) is an FDA approved treatment used in patients with intractable epilepsy. Intermittent voice alteration is commonly reported by patients following implantation of the device. In the second pivotal device study, 62% of patients at 3 months and 55% of patients at 12 months reported this side effect. In addition, reversible vocal cord paralysis was seen in two patients. The purpose of this study is to retrospectively determine if there are visible changes in vocal cord function by pre- and post-VNS implantation laryngoscopy. This is a retrospective chart review of patients implanted with the VNS device, who underwent pre-operative and post-operative laryngoscopy. Each patient underwent visualization and evaluation of larynx and vocal cord function. An attempt made to visualize these structures through at least one VNS activation cycle. Thirty-one patients met the criteria for inclusion into our study. 24 of the 31 patients (77%) were newly implanted patients. Another seven patients (23%) were revisions of previously implanted devices by other surgeons. In the newly implanted patients, 18/24 (75%) had normal pre-operative and post-operative vocal cord function on laryngoscopy. Five patients (21%) were noted to have decreased abduction and rhythmic contraction of the vocalis muscle on the left side when the VNS was activated. When the stimulator cycled off, vocal cord function returned to normal. One patient (4%) developed left sided vocal cord paralysis 11 months after implantation, which persisted after revision. Of the patients undergoing revision, 4/7 (57%) had no change in their vocal cord function following surgery. 2/7 (29%) patients had some mild worsening of left vocal cord function when the stimulator became active, but neither had subjective complaints. Four of 31 (13%) patients complained of dysphonia with activation of the stimulator, but there were no laryngoscopic changes noted. Two patients complained of neck discomfort from the stimulator, but did not require removal or turning off of the device. This retrospective study demonstrates that most patients undergoing vagus nerve stimulation device implantation have no demonstrable change with visualization of vocal cord function after surgery. Some patients had decreased left vocal cord function when the stimulator was active, but this effect resolved when the stimulator cycled off and did not cause any patient discomfort or problems. Also, our study demonstrates that most patients that undergo replacement of their VNS device have no change in their post-operative function. One of the patients developed left vocal cord paralysis 11 months after implantation, without a clear etiology. During replacement of the lead, there was no visible damage to the vagus nerve. Few of our patients complained of dysphonia.