V5-05: INTRAOPERATIVE PERIPROSTATIC NERVE ACTION POTENTIAL MONITORING DURING ROBOTIC PROSTATECTOMY

Video

Introductions and Objectives
Prostate cancer surgery involves interplay between the competing goals of extirpation of cancer, nerve sparing, and postoperative recovery of potency and continence. A surgeon’s task is further complicated by the complexity of periprostatic neuroarchitecture and fine nerves that are not readily visible, which places them at risk of inadvertent injury. Better intra-operative detection of nerve location in the peri-prostatic space can help in better nerve preservation, which is critical for improved functional outcomes after radical prostatectomy. We present a video of an ongoing feasibility clinical study to determine whether intraoperative nerve monitoring can locate these microscopic nerves during robotic radical prostatectomy (RP).

Methods
28 patients with a Sexual Health Index for Men (SHIM) questionnaire score of 17 or higher were prospectively enrolled into a single study-arm. All study patients received robotic RP with intraoperative nerve monitoring. A bipolar ball-tip probe directed by robotic needle drivers stimulated the periprostatic nerves. A modified Foley catheter with ring electrodes recorded the evoked nerve activity from within the urethra, distal to the apex of the prostate. The nerves were mapped circumferentially in the transverse plane of the prostate. Mapping was also attempted by reversing stimulating and recording electrodes: Stimulating from the Foley catheter ring electrodes and recording the retrograde nerve action potentials from the bipolar ball-tip probe. Following mapping, spontaneous nerve activity during dissection was monitored with the modified Foley catheter.

Results
All 28 enrolled patients underwent robotic RP according to the nerve monitoring protocol. In 3 patients (11%), evoked nerve action potentials were noted in response to stimulation. In 26 patients (93%), spontaneous nerve activity was recorded from the modified Foley catheter as the surgeon progressed with dissection. Spontaneous nerve activity was found to increase following surgical steps involving cautery or traction.

Conclusions
To our knowledge, this is the first study in which nerve action potentials have been recorded directly from the periprostatic nerves. The demonstrated increase in spontaneous nerve activity following cautery and traction supports use of athermal and traction-free dissection techniques. Further research and improvements in technology are needed to consistently record from these fine nerve fibers and to avoid potential false negatives.

Funding: This feasibility study was sponsored and funded by Medtronic, Inc.