Intraoperative nerve stimulation with measurement of urethral sphincter pressure changes during radical retropubic prostatectomy: A feasibility study

Purpose: We evaluated the feasibility of using intraoperative nerve stimulation and real-time urodynamic monitoring to identify the intrapelvic innervation of the urethral sphincter during radical retropubic prostatectomy. Materials and Methods: Using an intraurethral balloon pressure transducer and nerve stimulator changes in urethral pressure were measured in response to stimulation of the neurovascular bundles, pelvic side wall, bladder neck, rectus muscle and other structures in 8 patients undergoing nerve sparing radical retropubic prostatectomy. Intraurethral pressure changes were charted on an urodynamic monitor and correlated with the anatomical location of stimulation. Results: Stimulation of the neurovascular bundles resulted in measurable and significant (greater than 10 cm. H2O) increases in intraurethral pressure in all 8 patients. The mean pressure increase was 22 cm. H2O. Neither control structure, that is the bladder neck or rectus, resulted in pressure changes with stimulation. In 60% of the subjects pelvic side wall stimulation resulted in urethral pressure increases, while in 40% this stimulation caused pelvic contraction floor but no pressure increase. The mean pressure changes with side wall stimulation was 14 cm. H2O. Conclusions: Intraoperative stimulation of pelvic neural structures and measurement of changes in urethral pressure in response to stimulation are feasible during radical retropubic prostatectomy. Stimulating the neurovascular bundle consistently results in significant increases in urethral pressure. The finding of an intrapelvic urethral innervation supports the previously published observation that nerve sparing radical retropubic prostatectomy may result in improved continence postoperatively.