A. Shafik et S. Doss, Surgical anatomy of the somatic terminal innervation to the anal and urethral sphincters: Role in anal and urethral surgery, J UROL, 161(1), 1999, pp. 85-89
Purpose: The gross anatomy of the pudendal nerve branches was studied to id
entify more precisely the neuroanatomical relationship in the region of the
anal canal, bladder neck and proximal urethra. Such knowledge is essential
for the development of surgical techniques that avoid nerve injury in sphi
ncteroplasty for anal and urinary stress incontinence, and in pudendal cana
l decompression.
Materials and Methods: The pudendal nerve terminal branches were dissected
in 7 female and 5 male formalin fixed cadavers, including 6 fully mature ne
onates and 6 adults, a mean age of 37.6 years. The nerves were traced from
the pudendal nerve to their termination in the anal and urethral sphincters
, and pelvic floor muscles.
Results: The inferior rectal nerve occupied the lower half of the ischiorec
tal fossa. Immediately after emerging from the pudendal canal it extended a
motor branch to the levator ani muscle and the cutaneous perianal and scro
tal branches. The nerve terminated in the external anal sphincter at the 3
and 9 o'clock positions. Inside the pudendal canal the perineal nerve gave
rise to a scrotal branch which joined the scrotal branch of the inferior re
ctal nerve to form the common scrotal nerve. About 2 to 3 cm. from the pude
ndal canal the perineal nerve extended a branch to the bulbocavernosus musc
le and divided into the terminal scrotal and motor branches, which penetrat
ed the striated urethral sphincter at the 3 and 9 o'clock positions. The de
ep dorsal nerve of penis or clitoris coursed forward into the ischiorectal
fossa, emerged from the deep perineal pouch and penetrated the suspensory l
igament to the dorsum of the penis or clitoris.
Conclusions: The identification of the precise anatomical relation of the s
omatic nerve termination to the anal and urethral sphincters seems vital to
avoid sphincter denervation during surgery for the correction of fecal and
stress urinary incontinence.