Pudendal Neuralgia

Pudendal neuralgia is chronic neuropathic pain in the territory of the pudendal nerve (S2 to S4), felt in the perineum, genitalia and anorectal region, typically worse sitting and relieved by standing or lying. It is commoner in women, in cyclists and in people with pelvic trauma, surgery or childbirth.

Pathophysiology. Entrapment or injury of the pudendal nerve, most often between the sacrotuberous and sacrospinous ligaments, in Alcock canal, or from stretch during childbirth, produces neuropathic pain.

Burning, stabbing or aching pain in the perineum, vulva or penis, scrotum and anus, with a sensation of a foreign body in the rectum, allodynia, urinary urgency, sexual dysfunction and bowel symptoms. Pain is worse on sitting and eases on a toilet seat. Pain does not wake the patient from sleep. Examination shows no objective sensory loss.

Red flags.

• Saddle anaesthesia, retention or faecal incontinence.
• Fever, weight loss or a pelvic mass.

Diagnosis is clinical, using the criteria: pain in the pudendal territory, worse sitting, no waking at night, no objective sensory loss, and relief with a pudendal nerve block. MRI of the pelvis and lumbar spine excludes tumour, endometriosis, disc disease and other causes. Neurophysiology (pudendal motor latency, perineal electromyography) is of limited value. Diagnostic nerve block under ultrasound or CT imaging helps confirm.

Differential diagnosis.

• Chronic pelvic pain syndrome, interstitial cystitis and vulvodynia.
• Proctalgia fugax, levator ani syndrome and endometriosis.
• Cauda equina disease, sacral tumour and herpes zoster.

Start conservatively and escalate stepwise.

Self-management. Avoid prolonged sitting, use a cushion with a cut out, avoid cycling and heavy straining, and treat constipation.

Physiotherapy. Pelvic floor physiotherapy with relaxation and nerve gliding, avoiding strengthening exercises that increase muscle tone.

Drugs. Amitriptyline 10 mg at night, increased to 25 to 75 mg, gabapentin 300 mg daily, increased to 600 to 1200 mg three times daily (adjust to eGFR), pregabalin 75 to 300 mg twice daily, or duloxetine 30 to 60 mg daily. Topical lidocaine for allodynia.

Nerve blocks. Pudendal nerve block with local anaesthetic and corticosteroid, under imaging, up to three injections.

Further options. Botulinum toxin into pelvic floor muscles, pulsed radiofrequency, neuromodulation (sacral or pudendal), and surgical decompression for refractory cases with confirmed entrapment (success in about 60 to 70%).

Psychology. Cognitive and behavioural therapy for pain and sexual function.

Monitoring. Pain scores and function at 6 to 12 weeks.

Referral and escalation. Refer to pain medicine, urology, gynaecology or colorectal services.