Categories
Musculoskeletal System ORGAN SYSTEMS

Pudendal nerve entrapment syndrome (PNES)

Uncommon chronic pain, in which the pudendal nerve (located in the pelvis) is entrapped or compressed.

Introduction

Damage to the pudendal nerve can occur suddenly as a result of trauma to the pelvic region, prolonged bicycling, fractures or from falls.

Uncommon chronic pain, in which the pudendal nerve (located in the pelvis) is entrapped or compressed.

  • Also known as Alcock canal syndrome

Anatomy

Pudendal nerve:

  • Origin: S2, S3, and S4 roots of ventral rami of sacral plexus
  • Content: Sensory, motor, and autonomic fibers (however, injury causes sensory deficits more than motor)
  • Course:
    • Courses between piriformis and coccygeus muscles
    • Departs pelvic cavity through greater sciatic foramen ventral to sacrotuberous ligament
    • Passes medial to and under sacrospinous ligament at ischial spine level to re-enter the pelvic cavity through lesser sciatic foramen
    • Courses in the pudendal canal “Alcock canal”
    • Terminal branches (three) end in ischioanal fossa:
      1. Inferior rectal branch
      2. Perineal branch
      3. Dorsal sensory nerve of the penis/clitoris
Anatomical course and branches of the pudendal nerve: After its formation, the pudendal nerve descends and passes between the piriformis and ischiococcygeus muscles. It leaves the pelvis through the lower part of the greater sciatic foramen. It then crosses the sacrospinous ligament (close to its insertion to the ischial spine), and then re-enters the pelvis through the lesser sciatic foramen. After re-entering the pelvis, it accompanies the internal pudendal artery and vein, coursing anterosuperiorly through the pudendal canal (also known as Alcock’s canal – a structure formed by the fascia of the obturator internus muscle). Inside the pudendal canal, the nerve divides into branches, first giving off the inferior rectal nerve, then the perineal nerve, before continuing as the dorsal nerve of the penis or clitoris. | Grant, John Charles Boileau – An atlas of anatomy, / by regions 1962, Public Domain, https://commons.wikimedia.org/w/index.php?curid=31442151

Classification

Pudendal nerve compression based on anatomy:

The pudendal nerve entrapment syndromes subdivide into four types based on the level of compression.
  • Type I – Entrapment below the piriformis muscle as the pudendal nerve exits the greater sciatic notch.
  • Type II – Entrapment between sacrospinous and sacrotuberous ligaments is the most common cause of nerve entrapment.
  • Type III – Entrapment in the Alcock canal.
  • Type IV –  Entrapment of terminal branches.

Aetiology

Mechanical causes:

  • Pelvic surgery:
    • Pelvic organ prolapse (PoP) repair (M/C cause of pudendal neuralgia)
    • Mid-urethral sling surgery
    • Hysterectomy
    • Anterior colporrhaphy
  • Direct trauma to buttocks/back
  • Vaginal delivery
  • Chronic constipation
  • Excessive cycling: Chronic perineal microtrauma, which causes fibrosis in the pudendal canal and also the sacrospinous and sacrotuberous ligaments
  • Prolonged sitting

Non-mechanical causes:

  • Viral infections (herpes zoster, HIV)
  • Multiple sclerosis
  • Diabetes mellitus

Clinical faetures

  • Pain, numbness, and dysfunction in distribution of pudendal nerve (genitalia, rectum, and terminal urinary tract)
  • Sexual dysfunction: Persistent arousal, dyspareunia, vulvodynia, and male impotence
  • Sphincter dysfunction: Dyschezia, fecal incontinence, and urinary hesitancy
  • Foreign body sensation in the anus, rectum, urethra, or vagina.

Management

  • Conservative management:
    • Avoidance of painful stimulus
    • Lifestyle modifications
  • Physical therapy: Relaxation of pelvic floor muscles by releasing spasm and muscle lengthening
  • Pharmacologic therapy: Analgesics, muscle relaxants, and anticonvulsants (including gabapentin and pregabalin)
  • Pudendal nerve block: Local anesthetic/steroid infiltration
  • Surgical decompression: Definitive treatment for PNE
    • Approaches: Transperineal, transgluteal, transischiorectal, and laparoscopy
  • Neuromodulation: Latest treatment using a peripheral nerve stimulator, which causes stimulation of the pudendal nerve in the ischioanal fossa.
    • Pulsed radiofrequency: Newer neuromodulation technique and is considered safer than continuous radiofrequency ablation

Leave a Reply