High lead impedances requiring revision during vagal nerve stimulator generator replacement

Vagal nerve stimulation (VNS) therapy is among the growing options in the treatment of intractable epilepsy. The phenomenon of surprise lead impedance issues found at the time of surgery resulting in unplanned lead revision is a challenge with this type of device. We reviewed our experience with VNS revisions.

We retrospectively reviewed the records of all adult and pediatric patients between January 2009 and September 2018 who underwent surgery for VNS therapy, including revision surgery. Office and operative notes were reviewed to obtain the indications and operative details for VNS placement.

A total of 570 operations were reviewed. The indication was intractable epilepsy in all cases. Primary implantation was performed in 232 patients, while the remaining 338 cases were revision cases of various natures. Surprise high lead impedance was found in 10 (3%) of these cases, resulting in a significantly increased complexity of surgery in those instances.

Lead impedance issues can be caused by disconnection, electrode fracture, hardware failure, or tissue scarring but ultimately require a more extended surgery than may be initially planned. Anticipating the potential for a more extensive operation than a simple generator replacement may prevent perioperative frustrations on both sides.