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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Neurology

The Biology of PNES and Ruling Out Look-Alikes

At a Glance

Pudendal Nerve Entrapment Syndrome (PNES) is caused by physical compression of the pudendal nerve within narrow pelvic pathways, causing severe pain when sitting. Because the pelvic area is interconnected, PNES must be carefully distinguished from similar bladder, prostate, or lower back issues.

To understand Pudendal Nerve Entrapment Syndrome (PNES), it helps to visualize the “highway” the nerve travels through your pelvis. When this highway is obstructed, the result is chronic pain and dysfunction [1][2].

The Anatomy of the Pudendal Nerve

The pudendal nerve begins at the base of your spine, originating from the sacral plexus (specifically the S2, S3, and S4 nerve roots) [1][3]. As it travels through the deep structures of your pelvis, it splits into three main branches that provide sensation and control to vital areas:

  • The Inferior Rectal Nerve: Serves the anal canal and perianal skin [1][4].
  • The Perineal Nerve: Serves the perineum (the area between the anus and genitals) and the scrotum or labia [1][4].
  • The Dorsal Nerve of the Penis or Clitoris: Provides sensation to these highly sensitive areas [1][4].

Where the “Traffic Jams” Occur

Because this nerve weaves through narrow passages of bone, muscle, and ligament, there are three primary sites where it is most likely to become trapped or compressed [2][3]:

  1. The Interligamentous Space: This is the most common site of entrapment. The nerve passes through a gap between two major ligaments—the sacrospinous and sacrotuberous ligaments. If these ligaments are too close together or thickened, they can pinch the nerve like a pair of scissors [2][5][6].
  2. Alcock’s Canal (Pudendal Canal): This is a specialized tunnel made of connective tissue (fascia) along the pelvic wall. The nerve can become stuck if the tunnel narrows due to scarring, inflammation, or structural variations [1][7][6].
  3. The Falciform Process: A small, shelf-like extension of the sacrotuberous ligament can sometimes press against the nerve, adding another layer of compression [7][8].

Biological Drivers of Pain

PNES pain is driven by two main processes. First is mechanical compression, where the physical squeezing of the nerve prevents it from getting proper blood flow, leading to “ischemic” pain (pain from lack of oxygen) [2][6].

Second is neuropathic pain, where the nerve itself becomes damaged or hypersensitive. Over time, this can lead to central sensitization, a state where the nervous system stays in a high-alert mode, amplifying even minor sensations into significant pain [9][10][11].

Ruling Out “Look-Alike” Conditions

Because pelvic anatomy is so interconnected, several conditions can mimic PNES. Distinguishing them is crucial for getting the right treatment. Understanding what PNES is not is just as important as understanding what it is:

Condition How it differs from PNES
Interstitial Cystitis (IC/BPS) IC pain is usually related to bladder filling and is often relieved by urination. PNES pain is usually positional (worse when sitting) and unrelated to how full the bladder is [12][13].
Chronic Prostatitis (CP/CPPS) CP/CPPS often involves deep muscular aching or prostate-specific symptoms. While it overlaps with PNES, PNES is specifically tied to the territory of the pudendal nerve and is often confirmed by a diagnostic block [12][13].
Piriformis Syndrome This involves the sciatic nerve, not the pudendal nerve. Pain usually radiates down the back of the leg past the knee, whereas PNES pain stays concentrated in the pelvic/genital region [14][15].
Lumbosacral Radiculopathy This is a “pinched nerve” in the lower back (like a herniated disc). It typically follows a specific path down the leg and rarely causes the isolated genital burning or “golf ball” sensation seen in PNES [14][5].

Understanding that PNES is a specific anatomical and mechanical issue—rather than a generalized pelvic syndrome—allows you to target your discussions with doctors toward confirming the exact site of your nerve’s “traffic jam” using the criteria discussed in Getting an Accurate Diagnosis: The Nantes Criteria [2][16].

Common questions in this guide

What causes Pudendal Nerve Entrapment Syndrome (PNES)?
PNES occurs when the pudendal nerve is compressed or pinched as it travels through the pelvis. This typically happens in narrow anatomical pathways like the interligamentous space or Alcock's canal due to thickened ligaments, scarring, or inflammation.
How is PNES different from Interstitial Cystitis (IC)?
Interstitial cystitis pain is usually related to bladder filling and is often relieved by urinating. In contrast, PNES causes positional pain that typically gets worse when sitting and is not linked to how full the bladder is.
Can a pinched nerve in my lower back cause PNES symptoms?
A pinched nerve in the lower back typically causes pain that radiates down the back of the leg. It rarely causes the isolated genital burning or 'golf ball' sensation that is highly characteristic of pudendal nerve entrapment.
What areas of the body does the pudendal nerve control?
The pudendal nerve provides sensation and control to vital areas of the lower pelvis. It splits into branches that serve the anal canal, the perineum, and the genitals, which is why compression causes localized pain in these specific regions.
What is central sensitization in chronic pelvic pain?
Central sensitization happens when long-term nerve irritation keeps the nervous system in a state of high alert. This causes the brain to amplify even minor sensations into significant pain, complicating chronic conditions like PNES.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my symptoms, is it more likely that the compression is occurring in Alcock’s canal or the interligamentous space?
  2. 2.How can we distinguish my symptoms from Interstitial Cystitis or Chronic Prostatitis?
  3. 3.If my pain doesn't follow a clear dermatomal pattern down my leg, does that rule out lumbosacral radiculopathy?
  4. 4.Could central sensitization be playing a role in my pain, and how would that change my treatment plan?
  5. 5.Are there specific anatomical variants, like a thickened falciform process, that you look for on an MRI?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
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    [Intraoperative neurophysiological monitoring in radical prostatectomy and pudendal nerve surgical releasing.]

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    Archivos espanoles de urologia 2019; (72(8)):857-866.

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    Anatomic variations of pudendal nerve within pelvis and pudendal canal: clinical applications.

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    American journal of obstetrics and gynecology 2015; (213(5)):727.e1-6.

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    The Effect of Traction Force and Hip Abduction Angle on Pudendal Nerve Compression in Hip Arthroscopy: A Cadaveric Model.

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    Correlation between Anatomical Segments of the Pudendal Nerve and Clinical Findings of the Patient with Pudendal Neuralgia.

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    Laparoscopic transperitoneal pudendal nerve and artery release for pudendal entrapment syndrome.

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    Surgical endoscopy 2021; (35(11)):6031-6038 doi:10.1007/s00464-020-08092-4.

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    Pudendal Neuralgia: The Need for a Holistic Approach-Lessons From a Case Report.

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    Bladder Pain Syndome/Interstitial Cystitis due to Pudendal Nerve Compression: Described in 1915-A Reminder for Treating Pelvic Pain a Century Later.

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This page provides educational information about pudendal nerve anatomy and pelvic pain conditions. Always consult a qualified healthcare provider for an accurate diagnosis and to rule out other potential causes of your pain.

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