Anatomical Variants of the Pudendal Nerve Observed during a Transgluteal Surgical Approach in a Population of Patients with Pudendal Neuralgia.

Background: Several studies have described the course and anatomical relations of the pudendal nerve. Several surgical nerve decompression techniques have been described, but only the transgluteal approach has been validated by a prospective randomized clinical trial. The purpose of this study was to describe the course of the nerve and its variants in a population of patients with pudendal neuralgia in order to guide the surgeon in the choice of surgical approach for pudendal nerve decompression.

Objectives: In order to support the choice of the transgluteal approach, used in our institution, we studied the exact topography, anatomical relations, and zones of entrapment of the pudendal nerve in a cohort of operated patients.

Study Design: Observational study.

Setting: University hospital.

Methods: One hundred patients underwent unilateral or bilateral nerve decompression performed by a single operator via a transgluteal approach. All patients satisfied the Nantes criteria for pudendal neuralgia. The operator meticulously recorded zones of entrapment, anatomical variants of the course of the nerve, and the appearance of the nerve in the operative report.

Results: One hundred patients and 145 nerves were operated consecutively. Compression of at least one segment of the pudendal nerve (infrapiriform foramen, ischial spine, and Alcock's canal) was observed in 95 patients. The zone of entrapment was situated at the ischial spine between the sacrospinous ligament (or ischial spine) and the sacrotuberous ligament in 74% of patients.Anatomical variants were observed in 13 patients and 15 nerves. Seven patients presented an abnormal transligamentous course of the nerve (sacrotuberous or sacrospinous). A perineal branch of the fourth sacral nerve to the external anal sphincter was identified in 7 patients. In this population of patients with pudendal neuralgia, the pudendal nerve was stenotic in 27% of cases, associated with an extensive venous plexus that could make surgery more difficult in 25% of cases, and the nerve had an inflammatory appearance in 24% of cases.

Limitations: We obviously cannot be sure that the anatomical variants identified in this study can be extrapolated to the general population, as our study population was composed of patients experiencing perineal pain due to pudendal nerve entrapment and their pain could possibly be related to these anatomical variants, especially a transligamentous course of the pudendal nerve. The absence of other prospective randomized clinical trials evaluating other surgical approaches also prevents comparison of these results with those of other surgical approaches.

Conclusions: This is the first study to describe the surgical anatomy of the pudendal nerve in a population of patients with pudendal neuralgia. In more than 70% of cases, pudendal nerve entrapment was situated in the space between the sacrospinous ligament and the sacrotuberous ligament. Anatomical variants of the pudendal nerve were also observed in 13% of patients, sometimes with a transligamentous course of the nerve. In the light of these results, we believe that a transgluteal approach is the most suitable surgical approach for safe pudendal nerve decompression by allowing constant visual control of the nerve.Key words: Surgical, operative technique, pudendal, neuralgia, transgluteal approach.