Anatomical variations of the pudendal nerve
Pudendal neuralgia is an uncommon yet highly impactful condition of the pelvis and lumbar plexus that results in uncharacteristic symptoms and pain in the perineal and pelvic region. Damage can result from a variety of mechanisms including: stretch, compression or entrapment and is often assessed as a precipitating factor of pelvic floor pain in pre- and postnatal patients. To date, there has been poor characterization of the pudendal nerve (PN) and its surrounding tissues. Therefore, the authors undertook an extensive cadaveric dissection to shed light on the anatomical variations between patients. Overall, the authors discovered that there was significant variation of the number of PN trunks, as well as inclusion of the inferior rectal nerve (IRN) within the pudendal canal. Furthermore, there appeared to be a consistent fixation of the pudendal canal on the sacrospinous ligament (SSL), which could have significant clinical implications.
The PN is formed from the contributions of the second, third and fourth sacral nerves and provides both the motor and sensory distribution to the perineal region of the pelvis. Once formed, the nerve exits the pelvis through the greater sciatic foramen and travels on the posterolateral surface of the sacrospinous ligament, entering the perineum through the lesser sciatic foramen and coursing through the pudendal canal to its final divisions.
Detailed dissections using a transabdominal and perineal approach were carried out in thirteen unembalmed female cadavers (61-95 y/o). Measurements (diameter and length) were taken of both the pudendal nerve and inferior rectal nerve. Their association with the pudendal canal and sacrospinous ligament was also characterized.
Following dissection, it was shown that the PN was consistently formed from the contributions of the second, third and fourth sacral nerve roots. After coalescence, 61.5% of PN’s were found to have a single nerve trunk that entered the pudendal canal. The IRN entered the pudendal canal with the PN only 42.3% of the time. Surprisingly, it was revealed that the pudendal canal was consistently attached to the dorsal aspect of the SSL. The authors note that this could in turn result in an over-estimation of nerve entrapment as this is a conserved difference. While the concept of anatomical variation is not new, its existence helps shed light on possible factors involved in complex and non-responding populations.
> From: Maldonado et al., Am J Obstet Gynecol 213 (2016) 727(Epub ahead of print). All rights reserved to Elsevier Inc. Click here for the Pubmed summary.