The Pelvic and Sacral Splanchnic Nerves - Identification by Dissection, Trajectory.

The modern principles in pelvic surgery imply the preservation of the nervous structures that are involved in the physiological functioning of the pelvic and genital organs. The main pelvic nervous element is represented by the inferior hypogastric plexus. This plexus receives sympathetic afferent fibres from the hypogastric nerve, parasympathetic afferent fibres from the pelvic splanchnic nerves and also sympathetic afferent fibres coming from the sympathetic sacral chain via the sacral splanchnic nerves. We aimed to demonstrate the anatomy of these structures through dissection and we exposed the origins, pathway and manner of distribution of the splanchnic nerves of the pelvis. We managed to clarify the main anatomical relations of these nerves, among which we highlighted the relation to the branches of the internal iliac artery. The parasympathetic fibres reach the pelvis by running through the anterior rami of the spinal nerves, which are the origin of the sacral plexus. We managed to exhibit the way in which the parasympathetic fibres emerge from the sacral nerves and form the pelvic splanchnic nerves. Pelvic surgery nowadays is focused on nerve-sparing, which essentially means the conservation of the integrity of splanchnic nerves, hypogastric nerves and inferior hypogastric plexuses in order to maintain the normal functioning of the anatomical sphincters and genital organs. In this respect, it is crucial for the surgeon who performs pelvic procedures to be more than well-acquainted to the anatomy of the pelvic splanchnic nerves, which are considered to be the erectile nerves, and to that of the sacral splanchnic nerves.

The distribution of the inferior hypogastric plexus in female pelvis.

Elements that comprise the inferior hypogastric plexus are difficult to expose, intricate, and highly variable and can easily be damaged during local surgical procedures. We aimed to highlight, through dissection, the origin, formation, and distribution of the hypogastric nervous structures and follow them in the female pelvis. We performed detailed dissections on 7 female formalin-fixed cadavers, focusing on structures surrounding the pelvic organs. For each hemipelvis, we removed the peritoneum from the pelvic floor, and after we identified the hypogastric nerves, we continued our dissection towards the inferior hypogastric plexuses, following the branches of the latter. Laterorectally, the hypogastric nerves form the inferior hypogastric plexus, a variable structure - nervous lamina, neuronal network (more frequently), or sometimes a combination of them. We identified three components of the inferior hypogastric plexus. The anterior bundle travels towards the base of the urinary bladder, the middle part innervates the uterus and the vagina, and the posterior segment provides the innervation of the rectum. The plexus can be identified after removing the pelvic peritoneum and the subperitoneal adipose tissue. Intraoperatively, the structures can be preserved by using an immediately-subperitoneal dissection plane. The variable branches are relatively well-organized around the pelvic vessels, supplying the urinary bladder, the genital organs, and the rectum. The ureter is surrounded by some branches, especially in its last segment, and it also receives innervation directly from the hypogastric nerve. Close to the viscera, the nerves enter neurovascular plexuses, making the intraoperative separation of the nerves and the vessels virtually impossible.

Overview of the anatomical basis of the piriformis syndrome-dissection with magnetic resonance correlation.

The piriformis syndrome is one of the most commonly misdiagnosed causes of lower back and gluteal pain caused by the compression of the sciatic nerve and the internal pudendal neurovascular bundle by the piriformis muscle. Although this syndrome was first suggested over 90 years ago, its diagnosis still represents a challenge for clinicians. In the present study, dissection was used to determine the intra- and extrapelvic anatomical course of the internal pudendal nerve and the data were compared with the information obtainable through MRI examination, in order to identify the piriformis syndrome and to differentiate it from other causes of internal pudendal neuralgia. Thorough dissections of the pelvis and deep gluteal region were conducted on female cadavers, which were correlated with MRI scans, in order to describe the course of the internal pudendal nerve in contact with the piriformis muscle. The dissection findings and MRI scans obtained allowed us to describe and demonstrate the compression points along the course of the sciatic nerve and the internal pudendal bundle, the anatomical correlations between the piriformis muscle and the nervous structures around it, emphasizing the areas most susceptible to possible nerve impingement syndromes. In the anatomic trajectory of the sciatic nerve and the internal pudendal bundle there are multiple contact points with anatomical structures that may lead to compression of the nerve structures, generating symptoms that comprise the piriformis syndrome. The present study sought to establish clear osseous landmarks that may help evaluate these associations and possible nerve compressions on pelvic MRI examination.