A simple electrical approach to diagnosing a suspected lead break in patients with implanted vagus nerve stimulators...

Vagus nerve stimulation (VNS) is an effective adjunctive treatment for patients with drug-resistant epilepsy (DRE) or difficult-to-treat depression (DTD). The implanted system consists of a titanium-cased generator and a lead with platinum electrodes, placed around the cervical vagus nerve. In rare cases a lead may break, causing the patient to receive insufficient therapy or no therapy at all, with potentially dangerous consequences. In order to confirm a suspected lead breakage, physicians have the option to perform x-rays. However, x-rays often do not show a clear, unmistakable lead break. In this technical note an additional method to verify lead integrity electrophysiological is described in detail to provide the highest degree of certainty on the integrity of the lead when a broken lead is suspected before proceeding to revision surgery.

When patients introduce themselves with symptoms indicating a suspected lead breakage, a systematic lead break management is required. This includes, beside the clinical anamneses, performing VNS Therapy® System Diagnostics (SD). If an unacceptable HIGH lead impedance is observed, performing x-rays (anteroposterior and lateral views) may help to confirm a lead breakage. Additionally, EMG recording equipment can be used to analyse the VNS stimulus waveform from the neck for verification of an electrical discontinuity.

A differentiated VNS waveform with narrowed pulses or no waveform at all can confirm lead discontinuity.

This Technical Note describes an easy but underused electrophysiological procedure to be included in the standardized protocol for identifying VNS lead breakage.