Pudendal neuralgia

Pudendal nerve entrapment syndrome (PNE)

• an unusual cause of chronic pelvic pain, in which the pudendal nerve is entrapped or compressed
• pudendal neuralgia ("Alcock canal syndrome") is a symptom caused by pudendal neuropathy such as bowel, bladder, and sexual dysfunction, in addition to pain in the distribution of the pudendal nerve that is exacerbated on sitting.

Pathophysiology:

• pudendal nerve arises from the sacral plexus, and comprises the S2, S3, and S4 segments
  • a mixed nerve that supplies sensation to genitalia such as the penis, scrotum, clitoris, and labia, and innervates muscles of the perineum and pelvic floor
  • nerve exits through the greater sciatic foramen, crossing the ischial spine, the sacrospinous ligament, and the sacrotuberous ligaments
  • there are three common locations of nerve entrapment: between the sacrotuberal and sacrospinous ligaments, within the pudendal canal, and while crossing the falciform process of the sacrotuberal ligament
  • can also occur when the pudendal nerve is fused to nearby anatomical structures (2)
  • possible causes of pudendal neuralgia include excessive bicycling (often known as the "cyclist syndrome" (6)), pregnancy, anatomic abnormalities, scarring due to surgery, or as a sequela of radiation therapy (2)
  • affects both genders from childhood to nonagenerians

Clinical features:

• pudendal neuropathy secondary to nerve entrapment causes neuropathic pain with varying degrees of pain intensity in the S3-S4 dermatome
• pudendal nerve become entrapped at several points along its course leading to intractable pelvic and perineal hyperalgesia
  • other possible symptoms may include genital numbness and sexual dysfunction
• men may be erroneously considered to have "prostatitis"
• pain is typically caused by sitting, relieved by standing, and is absent when recumbent (lying down) or sitting on a toilet seat

Diagnosis of PNE is essentially clinical

• are no pathognomonic signs or specific tests (3)
  • 'Nantes criteria' are the diagnostic criteria of PNE, but they are not sufficient for all clinical situations (4)
    • Nantes criteria include
      • (1) pain in the anatomical territory of the pudendal nerve,
      • (2) which is worsened by sitting,
      • (3) the patient is not awakened at night by the pain,
      • (4) no objective sensory loss on clinical examination, and
      • (5) positive anesthetic pudendal nerve block
  • a detailed pain history and physical examination are necessary to distinguish PNE from pelvic pain of other cause
    
    
• performance of a pudendal nerve block can serve as both a diagnostic and therapeutic tool (2)
• imaging studies (for example MRI, MR neurography of the lumbosacral plexus and pelvic nerve branches), as well as the performance of an electrophysiological study with pudendal nerve motor latency testing, may yield valuable evidence in support of a pudendal neuralgia diagnosis

Management (1):

• no specific treatment for PNE is available
• management options include
  • physiotherapy
  • oral medications (options include amitriptyline, nonsteroidal anti-inflammatory drugs (NSAIDs), anticonvulsants, muscle relaxants, and opioids),
  • pudendal nerve block,
  • surgical nerve decompression

Reference:

• Lee JW et al. Pudendal Nerve Entrapment Syndrome due to a Ganglion Cyst: A Case Report. Ann Rehabil Med. 2016 Aug;40(4):741-4
• Elahi F et al. Pudendal entrapment neuropathy: a rare complication of pelvic radiation therapy.Pain Physician. 2013 Nov-Dec;16(6):E793-7.
• Rhame EE et al. Successful treatment of refractory pudendal neuralgia with pulsed radiofrequency. Pain Physician 2009;12:633-8.
• Tagliafico A et al. Contribution of ultrasound in the assessment of patients with suspect idiopathic pudendal nerve disease. Clin Neurophysiol 2014;125:1278- 84.
• Durante, JA., Macintyre, IG.Pudendal nerve entrapment in an Ironman athlete: a case report. J Can Chiropr Assoc. 54 2010 (4): 276-81