Electrical Resistance Increases at the Tissue-Electrode Interface as an Early Response to Nucleus Accumbens Deep Brain Stimulation

The therapeutic actions of deep brain stimulation are not fully understood. The early inflammatory response of electrode implantation is associated with symptom relief without electrical stimulation, but is negated by anti-inflammatory drugs. Early excitotoxic necrosis and subsequent glial scarring modulate the conductivity of the tissue-electrode interface, which can provide some detail into the inflammatory response of individual patients. The feasibility of this was demonstrated by measuring resistance values across a bipolar electrode which was unilaterally implanted into the nucleus accumbens of a rat while receiving continuous deep brain stimulation with a portable back-mounted device using clinical parameters (130Hz, 200 mu A, 90 mu s) for 3 days. Daily resistance values rose significantly (p<0.0001), while hourly resistance analysis demonstrated a plateau after an initial spike in resistance, which was then followed by a steady increase (p<0.05; p<0.0001). We discuss that the biphasic nature of the inflammatory response may contribute to these observations and conclude that this method may translate to a safe predictive screening for more effective clinical deep brain stimulation.