Variability of results of cavernous nerve stimulation during radical prostatectomy

Purpose: We assess the reliability of intraoperative cavernous nerve stimulation for producing an erectile response during radical prostatectomy. Materials and Methods: In 61 patients cavernous nerve function was assessed during radical retropubic prostatectomy using a CaverMap(double dagger) nerve stimulator. Control stimulation was also performed before and after prostatic dissection by placing the nerve stimulator tip on the anterior bladder wall. An increase in penile circumference measured by the device was considered a tumescence response while any measurable detumescence was also categorized. Results: Patient age ranged 43 to 72 years (mean 59.8). Before apical dissection 41% and 46% had tumescence, 31% and 21% had detumescence, and 28% and 33% had no response with stimulation of the neurovascular bundle and anterior bladder wall, respectively. After dissection 42% and 25% had tumescence, 16% and 18% had detumescence, and 42% and 57% had no response with stimulation of the neurovascular bundle and anterior bladder wall, respectively. Conclusions: A response to neurovascular bundle stimulation using this device does not necessarily correlate with the precise anatomical location of the cavernous nerves. There is considerable background variability related to anesthesia, surgical manipulation and other undefined factors that may cause minor but measurable changes in penile circumference.