Nerves at the Ventral Prostatic Capsule Contribute to Erectile Function: Initial Electrophysiological Assessment in Humans

Background: Recent microanatomical studies have identified a significant amount of nerve fibers along the ventral circumference of the prostate capsule and confirmed the concept of a periprostatic nerve network. However, functional investigations have not yet proved whether nerve fibers distributed on the prostate capsule, particularly those outside the neurovascular bundle (NVB), contribute to erection. Objective: To confirm whether nerve fibers distributed on the prostate capsule contribute to erectile function, the present study was performed using electrophysiologic testing. Design, setting, and participants: The circumference of the prostate capsule was electrically stimulated during radical retropubic prostatectomy (RRP) in 12 patients with clinically localized prostate cancer (PCa). We defined the ventromedian circumference of the prostate capsule as the 12 o'clock position and the posterolateral position of the typical NVB as the 5 o'clock position. Periprostatic nerve fibers at the 12, 1, 2, 3, 4, and 5 o'clock positions of the midprostate were stimulated using bipolar electrodes. Measurements: Changes in pressure at the middle of the urethra were measured using an inserted balloon catheter to detect increases in cavernosal pressure. Results and limitations: Although the study included only 12 patients, every stimulation at all positions between 1 and 5 o'clock evoked urethral pressure responses in all patients. Mean pressure response was most powerful for 5 o'clock stimulation and decreased with stimulated points further from the 5 o'clock position. Conclusions: We demonstrated that electrostimulation at not only the posterolateral but also the anterior and lateral circumference of the prostate capsule can increase cavernosal pressure. These findings indicate that the periprostatic nerve network contributes to erections.