Neuroanatomy of the External Urethral Sphincter: Implications for Urinary Continence Preservation During Radical Prostate Surgery

Abstract

Post-prostatectomy urinary incontinence probably is multifactorial and sphincteric nerve injury could be a contributing cause. Controversy still exists regarding the innervation of the external sphincter, and currently pudendal nerve injury is not believed to be an etiological factor in post-prostatectomy urinary incontinence. To understand better the sphincter and its innervation, we undertook an anatomical and histological study of 18 adult male cadavers, which revealed that the external urethral sphincter receives part of its innervation through special branches originating from the dorsal nerve of the penis after it splits from the pudendal nerve. These nerve branches were located 0.3 to 1.3 cm. from the prostatic apex, and in 50% of the cadavers they were identified only unilaterally or had only 1 branch on each side. The proximity of these nerves to the prostatic apex may make them liable to injury during radical prostatectomy. These nerves are most likely sensory in nature although the presence of motor components cannot be completely ruled out. Injury to these nerves may explain several features of post-prostatectomy urinary incontinence.

Veil Nerve-Sparing Technique and Postoperative Urinary Continence in Open Antegrade Radical Prostatectomy

“…The distance from the prostate apex to the entry point of the nearest pudendal neural branch to the sphincter is 3–13 mm. These statements, taken together, indicate that our Veil technique sparing the NVB from 2 to 10 o’clock (240°) and our method of cutting the urethra 2 mm apart from the apex would be an acceptable way to spare the nerve branches to the external urethral sphincter [22,30,31,32]. Our nerve IHC (S-100) results correlated with nerve sparing, better urinary continence, and earlier catheter removal, suggesting that, taken together, our Veil technique contributed to urinary continence based on our data of not only clinical but histological without compromising surgical margin status.…”

Absence of Urethral Post–Void Milking: An Additional Cause for Incontinence after Radical Prostatectomy?

“…Autonomic innervation travels throught the pelvic plexus and may be parasympathetic from the pelvic nerves and sympathetic from the superior hypogastric plexus [13, 14, 15]. In addition there is evidence that the rhabdosphincter receives dual somatic sensory innervation from the pudendal nerve, both from intrapelvic as well from extrapelvic branches [16, 17, 18]. …”

Anatomy of the Pelvis

“…It seems that the urethral sphincter in males, unlike to females, is independent of the muscle tone of the pelvic fl oor [ 31 ]. The distance of the point where the pudendal nerves enter the muscle differs from 3 to 13 mm [ 32 ]. The external sphincter has two parts: the external striated segment and the internal smooth muscle segment.…”