RECONSTRUCTIVE UROLOGY

Neuroanatomy of the human female lower urogenital tract
Yucel S, De Souza A Jr, Baskin LS
Department of Urology and Pediatrics, University of California-San Francisco Children’s Medical Center, University of California-San Francisco, San Francisco, California, USA
J Urol. 2004; 172: 191-5

• Purpose: The neuroanatomy of the female lower urogenital tract remains controversial. We defined the topographical anatomy and differential immunohistochemical characteristics of the dorsal nerve of the clitoris, the cavernous nerve and the nerves innervating the female urethral sphincter complex.
• Materials and Methods: A total of 16 normal female human pelvic specimens at 14 to 34 weeks of gestation were studied by immunohistochemical techniques. Serial sections were stained with antibodies raised against the neuronal markers S-100 and neuronal nitric oxide synthase (nNOS), vesicular acetylcholine transporter, calcitonin gene-related peptide and substance P. The serial sections were computer reconstructed into 3-dimensional images.
• Results: Under the pubic arch at the hilum of the clitoral bodies, the branches of the cavernous nerves joined the clitoral dorsal nerve to transform its immunoreactivity to nNOS positive. The cavernous nerves originated from the vaginal nervous plexus occupying the 2 and 10 o’clock positions on the anterolateral vagina and they traveled at the 5 and 7 o’clock positions along the urethra. The urethral sphincter complex was innervated by nNOS immunoreactive and nonimmunoreactive nerve fibers arising from the vaginal nervous plexus and pudendal nerve, respectively.
• Conclusions: The dorsal nerve of the clitoris receives nNOS positive branches from the cavernous nerve as a possible redundant mechanism for clitoral erectile function. The urethral sphincter complex has dual innervation, which pierces into the urethral sphincter complex at different locations. The study of the neuroanatomy of the female lower urogenital tract is germane to the strategic design of female reconstructive surgery.
  
  
• Editorial Comment
  This is the second paper on the neuroanatomy of the human clitoris of this group. They examined female human fetal pelvic specimens with regards to neural immunoreactivity. In an elegant study, they were able to demonstrate findings, which are important for some of the more recently available reconstructive techniques in women undergoing pelvic floor or pelvic surgery.
  nNOS immunoreactive nerve fibers were demonstrated in the distal clitoris but not in the proximal clitoris. It might be speculated that NO not only plays an important role in female sexual physiology but also that these specific nerves derive from the cavernous within the clitoral bodies and therefore are supplied by the pelvic autonomic nerves.
  The location of these autonomic pelvic nerves were seen at the level of the urethra at the 5 and 7 o’clock joining more cranially the more nervous complex located at the anterior lateral sides of the vagina at the 2 and 10 o’clock positions. There was also a nNOS non-immunoreactive but otherwise autonomic nerve entering the muscular layer of the urethral sphincter complex at the mid urethra. There were no other autonomic nerves seen in the mid urethra.
  The location of a dense network of autonomic nerves at the level of the vagina supplied by the inferior hypogastric plexus occupying the 2 and 10 o’clock positions at the rectum mainly at the lateral and anterior vaginal wall which were thinning out on the anterior wall towards the urethra. From there, fibers traveled either along the pathways described above towards the clitoris or towards the proximal a mid urethral sphincter.
  We learn from these studies for complex surgical procedures at the level of the pelvic floor and urethra to maintain micturition, continence and sexuality in female patients the preservation of autonomic nerves is mandatory and must put there pathways within the whole pelvis into consideration. Further studies will have to follow to demonstrate the functional value and possible changes in adulthood but definitely these data warned consideration during surgery.

Dr. Arnulf Stenzl
Professor and Chairman of Urology
Eberhard-Karls-University Tuebingen
Tuebingen, Germany