Topography of perineal nerve distribution: (a) iliohypogastric area; (b) pudendal nerve area; (c) inferior cluneal nerve area
Pudendal nerve area
Inferior cluneal nerve area
Third, the nature of the pain must be identified and carefully investigated:
Inflammatory pain: The pain is usually worse at night, causing sleep loss. No position eases the pain. Anti-inflammatory drugs can usually be effective in controlling the pain.
Mechanical pain: The physical position usually influences the pain (sitting or standing position) and the decubitus position alleviates the symptoms.
Fourth, associated symptoms (urinary dysfunction, obstructed defecation, vaginal dryness, fecal and urinary incontinence) are sometimes helpful to correlate the pain to a global syndrome such as myofascial syndrome or complex chronic pelvic pain syndrome. Skin lesions and scars must be carefully investigated. Local infection is a common condition and may influence the pain.
Finally, the history of medications and treatments offered to the patient must be investigated.
The physical examination and subsequent investigations should exclude anatomic scars and abnormalities that could be related to malignant and inflammatory pelvic disease. Moreover, the complete physical examination should give careful attention to any congenital disorder (dysmorphia) or anorectal malformation.
Investigations can include imaging, endoscopic, and functional investigations. Imaging is useful to exclude benign or malignant tumors. Vascular and inflammatory diseases can also be investigated and are helpful to confirm some diagnoses. Both computed tomography and magnetic resonance imaging are required standard imaging examinations. A particular focus on the lumbosacral spine is mandatory to identify anatomic abnormalities of the spine or compression of the cauda equine or lumbar and sacral roots. Particular attention must be paid to the presacral space, looking for possible tumors or bone metastasis.
Endoscopic investigations are useful to evaluate any mucosal abnormality. Colonoscopy, hysteroscopy, and cystoscopy should be performed based on associated symptoms and the topography of the pain.
Neurophysiological studies can be helpful in identifying nerve dysfunction. Pudendal nerve terminal motor latency, external anal sphincter electromyography, and the bulbospongiosus or clitoridoanal reflexes allow assessment of both the motor and sensory functions of the perineal and pelvic areas. Despite the value of these investigations, electromyography is invasive, and interpretation of the results may be difficult and related to the clinical features.
Several pain classifications are available in the literature (Table 35.1). The most common is based on the clinical characteristics of the pain.
Classification of nonorganic chronic pelvic and perineal pain
Pain influenced by the sitting position
Pain not influenced by the sitting position
Pudendal nerve entrapment
Sacral nerve irritation
Piriformis muscle syndrome
Obturator internis muscle syndrome
Inferior cluneal (perineal) nerve syndrome
Paroxystic algias (proctalgia fugax)
Levator ani syndrome
35.5.1 Pain Influenced by the Sitting Position
126.96.36.199 Pudendal Nerve Entrapment
Pudendal nerve entrapment is the most frequent and best described cause of chronic pelvic pain. The topography of the pain is typically medial or unilateral and localized between the penis and the anus (in men) or the clitoris and the anus (in women). In men, the pain usually does not involve the scrotum or the testicles. The onset of pain occurs after a physical effort made while in a sitting position, such as cycling; this is typical of the pudendal nerve entrapment. Nevertheless, in several cases pain can occur with no particular triggering event. Pain is described as a burning or strangling feeling, either superficially or deep inside the perineum in the ipsilateral nerve area. It can be associated with signs of hypersensitivity upon touching the skin. A trigger zone can be found during the rectal digital examination portion of the physical exam, at the level of the ischial spine or sometimes while pressing the levator ani muscle.
A diagnosis is based on clinical findings, associated with improvement of the symptoms after pudendal nerve infiltration around the entrapment area at the ischial spine (Nantes criteria; Table 35.2). A diagnosis is also supported by the finding of prolonged pudendal nerve motor latency on electrophysiological studies.
Nantes criteria for pudendal nerve entrapment
1. Pain in the territory of the pudendal nerve, from the anus to the penis or clitoris
2. Pain is predominantly experienced while sitting
3. The pain does not wake the patient at night
4. Pain with no objective sensory impairment
5. Symptoms are relieved after a pudendal nerve block
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