Objectives. The external striated urethral sphincter (rhabdosphincter)
is a tubular muscle sleeve that extends from the prostate-membranous
urethra and perineal membrane to the bladder neck. The male rhabdosphi
ncter neuroanatomy remains unclear, and a better understanding of its
innervation may provide insight into potential modifications of radica
l pelvic surgery to improve urinary continence. Methods. Fresh cadaver
ic dissections of 12 male hemipelves were undertaken to investigate th
e neuroanatomy of the urinary rhabdosphincter. Results. Neuroanatomic
courses of the nerve supply to the rhabdosphincter revealed that, in t
he perineum, the perineal nerve (a terminal branch of the pudendal ner
ve) provided branches directly to the bulbospongiosus muscle and the u
rinary rhabdosphincter. In the pelvis, the course of the pelvic nerve
was as follows: (1) arising from the inferior hypogastric plexus, it h
ad a weblike course beneath the muscle fascia of the levator ani muscl
e; (2) traveling posterolateral to the rectum, it gave many branches t
hat perforated into the lateral rectum; and (3) at the level of the pr
ostatic apex, still beneath the levator ani muscle fascia (superior fa
scia), it sent multiple direct branches to the inferolateral aspect of
urinary rhabdosphincter. The pudendal nerve traversed the pelvis in t
he pudendal canal, and, before leaving the pelvis to enter the perineu
m, it gave an intrapelvic branch that courses with the pelvic nerve to
innervate the rhabdosphincter. Conclusions. Our understanding of the
neuroanatomy of what may be the continence nerves has been improved by
fresh cadaveric dissection. The rhabdosphincter receives nerve fibers
from the pelvic nerve and dual innervation from an intrapelvic branch
and a perineal branch of the pudendal nerve. Better understanding of
these anatomic findings may have potential surgical significance with
respect to improvement in postoperative urinary continence. (C) 1997,
Elsevier Science Inc.