Auscultation of the implantable pulse generator and identifying a clinical correlate of high impedance in deep brain stimulation systems: case report

Impedance values exceeding 10,000 Ω are a recognized indicator of hardware failure in deep brain stimulation (DBS) systems. However, impedance assessment relies exclusively on programmer-mediated telemetry conducted by trained neuromodulation specialists with access to manufacturer-specific equipment. When symptoms worsen or therapeutic benefit declines, a clinically accessible correlate of elevated impedance would facilitate timely evaluation of complications including system malfunction. In this study, we report the reproducible detection of high impedance by auscultating the implanted pulse generator (IPG). Stimulation through high impedance contacts (>10,000 Ω) was consistently distinguishable from normal-impedance contacts, and when the IPG was turned off, using a standard stethoscope, across patients. Spectral analysis of the auscultatory signal was performed for further characterization. Analysis demonstrated discrete, high-amplitude peaks at integer harmonics of the programmed stimulation frequency, consistent with nonlinear transduction within the system. These high amplitude harmonics were absent under normal conditions. These findings demonstrate an association between high impedance and an accessible clinical correlate. While a larger cohort study is needed to validate the clinical utility of this association, this case describes how auscultation with a stethoscope can represent a simple, non-invasive adjunct for detecting hardware failure in an implanted DBS system.