Vagus nerve stimulation: Surgical technique of implantation and revision and related morbidity

Abstract

SUMMARYIndications for vagus nerve stimulation (VNS) therapy include focal, multifocal epilepsy, drop attacks (tonic/atonic seizures), Lennox-Gastaut syndrome, tuberous sclerosis complex (TSC)-related multifocal epilepsy, and unsuccessful resective surgery. Surgical outcome is about 50-60% for seizures control, and may also improve mood, cognition, and memory. On this basis, VNS has also been proposed for the treatment of major depression and Alzheimer's' disease. The vagus nerve stimulator must be implanted with blunt technique on the left side to avoid cardiac side effects through the classic approach for anterior cervical discectomy. The actual device is composed of a wire with three helical contacts (two active contacts, one anchoring) and a one-pin battery. VNS is usually started 2 weeks after implantation with recommended settings of stimulation (1.0-2.0 mA; 500 ls pulse width; 20-30 Hz; 30 s ON, 5 min OFF). The complications of VNS therapy are early (related to surgery) and late (related to the device and to stimulation of the vagus nerve). Early complications include the following: intraoperative bradycardia and asystole during lead impedance testing, peritracheal hematoma, infections (3-8%), and vagus nerve injury followed by hoarseness, dyspnea, and dysphagia because of left vocal cord paralysis. Delayed morbidity due to the device includes late infections or problems in wound healing; other more rare events are due to late injury of the nerve. Late complications due to nerve stimulation include delayed arrhythmias, laryngopharyngeal dysfunction (hoarseness, dyspnea, and coughing), obstructive sleep apnea, stimulation of phrenic nerve, tonsillar pain mimicking glossopharyngeal neuralgia, and vocal cord damage during prolonged endotracheal intubation. The laryngopharyngeal dysfunction occurs in about 66% of patients and is usually transitory and due to the stimulation of the inferior (recurrent) laryngeal nerve. A true late paralysis of the left vocal cord is often partial and rare (1-2.7%), and usually transitory, and may be caused by previous surgical trauma (i.e., damage of nerve fibers and/or of their blood supply) or to a supposed chronic denervation during stimulation. Surgery for complete removal or revision and replacement of the device is to be considered in cases of device malfunction (4-16.8%), failure of VNS therapy, intolerable side effects, or because of patient's specific request. As described in the literature, the surgical techniques of lead revision and replacement are two: sharp and blunt dissection of helical electrodes and replacement; and blunt dissection combined with ultrasharp low-voltage cautery dissection. The incidence of left vocal cord palsy after vagus nerve stimulator replacement/revision is slightly higher than that of first implantation (4.9% vs. 3.8%). A de novo implantation in a naive segment of the left or right vagus nerve may be considered in specific cases; the use of the right vagus nerve is a rare exception that may be chosen with an acceptable result.

Review article: the role of the autonomic nervous system in the pathogenesis and therapy of IBD

“…Other complications include vagus nerve injury, delayed wound healing, dyspnoea (from left vocal cord paralysis) and cough. Transient hoarseness (from stimulation of the recurrent laryngeal nerve) can occur in around 66% of patients but is transient during periods of stimulation . These side effects, albeit rarer when in the hands of experienced practitioners, must be considered alongside any benefit the device is thought to give to the patient.…”

Cervical vagal nerve stimulation impairs glucose tolerance and suppresses insulin release in conscious rats

“…In these conditions the cervical vagus nerve is chronically stimulated through an implanted device (Giordano et al. ) and the therapeutic effects are thought to be mediated through afferent signaling to the central nervous system (Groves and Brown ; Krahl and Clark ). However, in a previous study (Meyers et al.…”

“…Currently, VNS is FDA-approved for the treatment of therapy-refractory epilepsy (Nune et al 2015) and major depression (Cristancho et al 2011). In these conditions the cervical vagus nerve is chronically stimulated through an implanted device (Giordano et al 2017) and the therapeutic effects are thought to be mediated through afferent signaling to the central nervous system (Groves and Brown 2005;Krahl and Clark 2012). However, in a previous study (Meyers et al 2016), we demonstrated that afferent signaling evoked by cervical VNS inhibits insulin secretion and markedly increases resting blood glucose levels in anesthetized rats, raising the question if patients treated with cervical VNS are at risk of developing glucose intolerance.…”

Pharyngolaryngeal spasm‐induced dysphagia in an epileptic patient undergoing vagus nerve stimulation therapy

“…Our experience shows that the close collaboration between ENT surgeons and epileptologists, able to combine the anatomical knowledge of the cervical region and endoscopic access to the side effects site with the electrophysiological knowledge of the VNS, is essential for the reaching of this goal. Surgery for complete removal or revision and replacement of the device should be regarded as an extreme measure, to be considered only in cases of device malfunction (4%‐16.8%), failure of VNS therapy, intolerable side effects, or patients' specific requests …”

“…Early complications consist in intraoperative bradycardia (1/1000 cases), infections (3%‐8%), and VN injury. Late complications consist mainly in laryngeal dysfunction with hoarseness, dyspnoea and cough, usually related to the frequency of stimulation, vocal fold palsy, laryngopharyngeal reflux, and obstructive sleep breathing disorders . While most of these alterations have been related to the variation of vocal cord movements during stimulation or to the orthodromic effect of VN stimulation, no study associated, at present, abnormal laryngopharyngeal movements with dysphagia symptoms, which are nevertheless well‐known in VNS patients.…”