Pudendal Nerve: Caught in the Space Between

My 6 year old girl (going on 13) asks “Alexa” to play the Descendants II soundtrack over and over again. So the song, “Space Between,” was lingering in my head while reading the most recent articles on pudendal neuralgia, particularly when pudendal entrapment is to blame. After all, entrapment, by medical standards, describes a peripheral nerve basically being caught in between two surrounding anatomical structures.

Ploteau et al., (2016) presented 2 case studies highlighting the warning signs when pudendal nerve entrapment does not follow the Nantes criteria. A brief summary of those 5 criteria follows:

• Pain in the region of the pudendal nerve innervation from anus to penis or clitoris.
• Pain most predominant while sitting.
• The patient does not wake at night from the pain.
• No sensory impairment can be objectively identified.
• Diagnostic pudendal nerve block relieves the pain.

The case studies of a 31 and a 68 year old female revealed endometrial stromal sarcoma and adenoid cystic carcinoma in the ischiorectal fossa, with night pain was noted in both patients, as well as no pain with sitting or defecation, respectively. Clinicians must always be mindful to resolve red flags in patients.

In 2016, Florian-Rodriguez, et al., studied cadavers to determine the nerves associated with the sacrospinous ligament, focusing on the inferior gluteal nerve. Fourteen cadavers were observed, noting the distance from various nerves to the sacrospinous ligament (from a pelvic approach) and to the ischial spine (from a gluteal approach). The S3 nerve was closest to the sacrospinous ligament, and the pudendal nerve was the closest to the ischial spine. In 85% of subjects, 1 to 3 branches from S3/S4 nerves pierced or ran anterior to the sacrotuberous ligament and pierced the inferior part of the gluteus maximus muscle. The authors concluded the inferior gluteal nerve was less likely to be the source of postoperative gluteal pain after sacrospinous ligament fixation; however, as the pudendal nerve branches from S2-4, it was more likely to be implicated in postoperative gluteal pain.

A study by Ploteau et al. (2017) explored the anatomical position of the pudendal nerve in people with pudendal neuralgia. In 100 patients who met the Nantes criteria, 145 pudendal nerves were surgically decompressed via a transgluteal approach. At least one segment of the pudendal nerve was compressed in 95 of the patients, either in the infrapiriform foramen, ischial spine, or Alcock’s canal. In 74% of patients, nerve entrapment was between the sacrospinous ligament and the sacrotuberous ligament. Anatomical variants were found in 13% of patients, often with a transligamentous course of the nerve.

When the pudendal nerve is caught in the narrow space between ligaments in the pelvis, diagnosing the source of pain is paramount. Research supports a gluteal approach in releasing the entrapped nerve. Post-surgical care falls into the hands of pelvic floor therapists, so taking “Pudendal Neuralgia and Nerve Entrapment: Evaluation and Treatment” may be something to consider in order to provide optimal care.

Ploteau, S, Cardaillac, C, Perrouin-Verbe, MA, Riant, T, Labat, JJ. (2016). Pudendal Neuralgia Due to Pudendal Nerve Entrapment: Warning Signs Observed in Two Cases and Review of the Literature. Pain Physician. 19(3):E449-54
Florian-Rodriguez, ME, Hare, A, Chin, K, Phelan, JN, Ripperda, CM, Corton, MM. (2016). Inferior gluteal and other nerves associated with sacrospinous ligament: a cadaver study. American Journal of Obstetrics and Gynecology. 215(5):646.e1-646.e6. doi: 10.1016/j.ajog.2016.06.025
Ploteau, S, Perrouin-Verbe, MA, Labat, JJ, Riant, T, Levesque, A, Robert, R. (2017). Anatomical Variants of the Pudendal Nerve Observed during a Transgluteal Surgical Approach in a Population of Patients with Pudendal Neuralgia. Pain Physician. 20(1):E137-E143