Elevated Electrode Impedances During Deep Brain Stimulation Surgery May Be Due to Peri-Electrode Air Collections

Deep brain stimulation (DBS) is a commonly used treatment for medically refractory movement disorders and epilepsy. Intraoperative testing of electrode impedances is routinely done during DBS surgery to identify electrical conduction defects in the system. We present two illustrative cases involving elevated intraoperative impedances. In the first case, the temporal evolution of impedance changes and a postoperative head CT were consistent with a small and slowly resolving air collection along the lead. In the second case, an abnormally high impedance reading was observed at a single electrode and then "transferred" to be observed at an adjacent electrode upon adjustments of the electrode position, likely due to small air collection at a fixed position in the brain tissue. In both cases, careful troubleshooting allowed identification of the issue and avoidance of unnecessary surgical revisions. A thorough understanding of the possible sources of, and troubleshooting for, abnormal impedance readings is needed for effective intraoperative DBS monitoring.