Circuit failure and revision surgery after vagus nerve stimulator implantation: a report of six cases

Abstract

Objective To summarize the common causes and types of circuit failure after vagus nerve stimulator(VNS)implantation, and analyze the available methods of resolving these problems. Methods Three patients with postoperative circuit fault in the 97 patients performed VNS implantation for drug refractory epilepsy in our hospital from October 2011 to January 2014, and three patients with postoperative circuit fault performed surgery in other hospitals at the same period were chosen in this study. The causes of circuit failure of these 6 patients were identified by performing system diagnostics and X-ray evaluation. A revision surgery may be necessary if a broken or damaged lead was suspected. Results In these 6 patients of device failure, two patients were due to the disconnection of the lead from the pulse generator; the lead impedance became normal after re-inserting the existing lead connector pins into the pulse generator following proper lead insertion techniques. Four patients performed lead revision surgery to replace or remove the existing lead; in 3 of them, the helices and associated scar tissues were removed from the vagus nerve under the microscope, and a new set of electrodes was placed; in one of them, the lead was transected as much as possible and the distal portion of the lead was severed at the neck following the removal of pulse generator. There were no complications such as hoarse voice, dyspnea, slow rhythm, subcutaneous hematoma or infection after the revision surgery. Five patients were followed up, indicating the devices work normally. Four patients had obvious improvement, and one patient had no significant improvement after the revision surgery. Conclusions The high lead impedance is the main manifestation of circuit failure after vagus nerve stimulator implantation. Surgical exploration is an effective method to identify and resolve these problems. Key words: Vagus nerve stimulation; Circuit failure; Pulse generator; Lead; High electrode impedance