(153) Intrapelvic Localizations of Erectogenic Nerves During Radical Prostatectomy Using Grid Electrodes

Introduction In the quest to improve functional outcomes after radical prostatectomy (RP), attention has been brought to developing intraoperative techniques for preserving the integrity of the periprostatic cavernous nerves that mediate the erection response. As cavernous nerve mapping during RP is developed within a platform of intraoperative neurophysiologic monitoring, the adjunctive use of intrapelvic grid electrode technology is proposed for neural stimulation and recording. Objective We aimed to demonstrate localization of erectogenic cavernous nerves in response to neurostimulation using grid electrode technology in a pilot investigation of patients undergoing RP. Methods We conducted a non-interventional, IRB-approved study designed for real time in operando localization of cavernous nerves during open (n = 5) and robot-assisted (n = 3) RP surgeries. Lumbosacral neurostimulation (10-80 mAmps, 150-1500 Hz, 100 usec), using needle electrodes inserted preoperatively at L4-L5 vertebral level, elicited cavernous nerve signal impulses, which were recorded as action potentials (AP) using specially designed grid electrode arrays (various size ranges of platinum electrodes at 2 mm intervals) positioned after retropubic exposure overlying the prostate and off-midline of the prostate extending to the pelvic floor bilaterally. Recordings of an “origin of neurological activity” were obtained at baseline prior to prostate dissection. Localizations applied a bipolar montage (paired electrodes) technique and were based on signal response latency, (msec) amplitude (uV), and polarity. Results Experiment 1: Neurovascular bundle (posterolateral prostate location). A generally consistent pattern of AP signals was recorded, anteriorly from midline to lateral: amplitudes of 400-500 uV at 2-4 mm, 890-1015 uV at 8-12 mm (posterolateral prostate), 200-280 uV at 14-22 mm (pelvic floor). Notably, AP amplitude measurements varied side to side in individual subjects and between subjects. Response latency was 5.2 – 8.2 msec, without showing a consistent pattern. Experiment 2: Dominant neural signal (variable localizations across subjects). The change in amplitude per mm distance from the nerve was 80-200 uV (12-30% decrement per mm). Reverse polarity in waveforms opposite to others in a series contributed to nerve localization. Conclusions Grid electrode technology is plausibly used in the performance of RP for cavernous nerve mapping. AP recordings are the primary measure of localization within an accuracy of 1mm. Because of intersubject and intrasubject variability in cavernous nerve distribution, this technology is potentially applicable on an individualized basis. Ongoing studies will involve grid arrays having additional electrodes for more refined nerve localizations. Disclosure Yes, this is sponsored by industry/sponsor: Neurovascular Research & Design Clarification: Industry funding only - investigator initiated and executed study