Pudendal Neuralgia

Anatomy

1. Exits the pelvis through the greater sciatic foramen (below piriformis)
2. Wraps around the ischial spine and posterior sacrospinous ligament
3. Re-enters the pelvis through the lesser sciatic foramen
4. Travels through the pudendal canal (Alcock's canal) — a fascial tunnel on the medial aspect of the obturator internus muscle — where it divides into its three terminal branches:
   • Inferior rectal nerve (anal canal, external sphincter, perianal skin)
   • Perineal nerve (scrotum/labia, perineal muscles, urogenital diaphragm)
   • Dorsal nerve of the clitoris/penis

MR Neurography of Pudendal Neuropathy

Etiology & Risk Factors

Pudendal neuropathy from perineal descent syndrome is caused by stretching and entrapment of the nerve, evidenced by elongation, prolonged pudendal nerve motor terminal latency (PNTML), and decreased anal sensation. — Berek & Novak's Gynecology

Clinical Features

• Burning, sharp, aching, or electric shock-like pain
• Paresthesia/numbness in perineum, vulva/scrotum, clitoris/penis, perianal region, distal urethra
• Typically unilateral (though bilateral occurs)
• Allodynia — pain from non-painful stimuli (e.g., clothing contact)

• Pain worsened by sitting (classically, sitting on a toilet is less painful than a hard chair — the central perineum is unloaded)
• Pain relieved by standing or lying down
• Pain does not wake the patient from sleep (a distinguishing feature)
• Exacerbated by hip flexion, exercise, straining
• Associated urinary symptoms: urgency, frequency, dysuria
• Sexual dysfunction: dyspareunia, ejaculatory pain, erectile dysfunction

Diagnosis: Nantes Criteria

"It is not possible with examination or imaging to completely differentiate pudendal entrapment from neuralgia related to nerve injury." — Berek & Novak's Gynecology, p. 596

Examination Findings

• Maximum tenderness near the ischial spine and Alcock's canal on vaginal/rectal palpation
• Confirmatory diagnostic nerve block: 3–5 mL of 0.25% bupivacaine at ischial spine; ≥50% relief is diagnostic

Electrodiagnostics

• Pudendal nerve motor terminal latency (PNTML): prolonged in entrapment/stretch injury
• Limited sensitivity; normal PNTML does not exclude PN

Imaging

• MR neurography (3T): emerging gold standard — detects T2 hyperintensity and nerve enlargement in Alcock's canal; also useful for pre-surgical planning
• DTI tractography: allows 3D mapping of nerve course; a 2024 systematic review (PMID 38797289) found DTI of the lumbosacral plexus is feasible and may offer prognostic and preoperative value, though normative values for pudendal nerve microstructure are not yet established
• CT/MRI: exclude structural causes (tumors, cysts, sacral lesions)

Management

Conservative (First-Line)

Interventional (Second-Line)

• CT- or ultrasound-guided injection at ischial spine or within Alcock's canal
• Local anesthetic ± corticosteroid
• Both diagnostic and therapeutic
• Campbell-Walsh Wein notes: "pudendal nerve blocks applied by trained clinicians may be helpful therapy and can also aid in diagnosis" in pelvic pain conditions

• Applied to pudendal nerve; neuromodulatory rather than ablative
• A 2025 meta-analysis (PMID 39607531) found PRF, injections, and surgery all improved pain to a similar extent (mean VAS reduction ~2.73 cm), with no statistically significant difference between modalities

• Sacral neuromodulation (S3 stimulation), posterior tibial nerve stimulation, and direct pudendal nerve stimulation
• A 2024 systematic review (PMID 38365090) supports electrical stimulation as a viable option

Surgical (Third-Line)

Key caveat: Surgery benefits entrapment — not pure nerve injury. Since these cannot be fully distinguished clinically, appropriate patient selection is critical.

Differential Diagnosis

• Vulvodynia / vestibulodynia (no nerve block response)
• Coccydynia
• Interstitial cystitis/bladder pain syndrome
• Levator ani syndrome / pelvic floor myofascial pain
• Piriformis syndrome
• Sacral nerve root compression (radiculopathy — would show sensory deficits, distinguishing it from PN)
• Prostatitis / chronic pelvic pain syndrome (men)
• Pelvic congestion syndrome

Summary of Recent Evidence (2024–2025)

• Berek & Novak's Gynecology, pp. 595–596 (Nerve Entrapment; Nantes Criteria)
• Berek & Novak's Gynecology, p. 172 (Pudendal nerve anatomy)
• Campbell-Walsh-Wein Urology (IC/BPS and pudendal nerve blocks)
• PubMed systematic reviews: PMIDs 39607531, 38942945, 38797289, 38365090

Primary Infertility with Tubal Block — Investigations & Management

Step 1 — Establish the Diagnosis of Primary Infertility

Step 2 — Initial Workup (All Couples)

Female Partner

Male Partner

Step 3 — Tubal Assessment

3a. Non-invasive / First-line

• High titres predict tubal damage; can triage patients before imaging
• Negative CAT in a low-risk patient makes significant tubal disease less likely

3b. Tubal Patency Testing (Imaging)

HSG: (a) bilateral proximal tubal occlusion; (b–d) selective salpingography with guidewire recanalization; (e) bilateral patency restored after cannulation.

3c. Definitive Assessment

• Gold standard for tubal patency and pelvic pathology
• Methylene blue or indigo carmine dye injected through cervix; spill observed laparoscopically from fimbriae
• Simultaneously diagnoses endometriosis, pelvic adhesions, peritubal disease
• Indicated when: HSG/HyCoSy shows block, history suggests pelvic inflammatory disease (PID), endometriosis, prior pelvic surgery, or high CAT titres

• Fiberoptic visualization of tubal ostia and intratubal mucosa (via hysteroscopy)
• Identifies intraluminal pathology (debris, mucosal agglutination)
• Limited by technical complexity and perforation risk; not routine

Step 4 — Treatment Based on Site and Severity of Block

A. Proximal Tubal Occlusion (PTO)

• Performed via HSG-guided selective salpingography (fluoroscopic) or hysteroscopy + laparoscopy
• Passes a soft catheter into the tubal ostium; a guidewire is advanced to overcome obstruction
• Restores patency in up to 85% of cases
• Reocclusion rate ~30%; re-cannulation or IVF then considered
• Ongoing pregnancy rates: 12–44%
• Tubal perforation in 1.9–11% (usually minor)

• Spasm, stromal edema, amorphous debris, mucosal agglutination, viscous secretions

• Luminal fibrosis, TB, congenital atresia, failed prior reanastomosis, fibroids

• Via laparotomy: excision of blocked isthmus, reimplantation into new cornual opening
• Reported pregnancy rates up to 68% in small series
• Reserved for specific cases; IVF preferred in most

B. Distal Tubal Occlusion

Ectopic pregnancy risk after distal tubal surgery: ~7.9% — Berek & Novak's Gynecology, p. 2061

C. Hydrosalpinx (Distal Occlusion with Fluid Collection)

• Meta-analysis (14 studies, 1,004 patients): IVF pregnancy rates significantly lower in the presence of hydrosalpinges
• Salpingectomy prior to IVF significantly improves both pregnancy and live birth rates compared to IVF with tubes in situ
• Laparoscopic tubal occlusion (proximal ligation/clipping) is a reasonable alternative to salpingectomy when salpingectomy is technically difficult
• Transvaginal needle aspiration and salpingostomy have less outcome data — not preferred

Key principle: If proceeding to IVF with hydrosalpinx, treat the hydrosalpinx first. — Berek & Novak's Gynecology, p. 2062

D. IVF (In Vitro Fertilization)

• Severe/bilateral disease
• Failed surgical correction or reocclusion
• Age ≥35 or diminished ovarian reserve
• Additional male factor or anovulation
• Tuberculous salpingitis (surgery ineffective)

"As success rates for ART continue to improve, the indications for surgical approaches in the treatment of tubal infertility have become increasingly limited." — Berek & Novak's Gynecology, p. 2060

Surgical Approach Summary

Management Algorithm

Primary Infertility with Suspected Tubal Block
│
├── Full couple workup (semen analysis, ovarian reserve, uterine cavity)
│
├── Tubal patency assessment
│   ├── HSG / HyCoSy / HyFoSy (first-line)
│   └── Laparoscopy + chromopertubation if HSG abnormal or high clinical suspicion
│
├── PROXIMAL BLOCK
│   ├── Tubal cannulation (HSG-guided or hysteroscopic)
│   │   └── Success → TI / IUI; Failure/reocclusion → IVF
│   └── True fibrosis/TB → IVF directly
│
├── DISTAL BLOCK / ADHESIONS
│   ├── Age <35, mild disease, good ovarian reserve → Laparoscopic surgery
│   │   (adhesiolysis / fimbrioplasty / salpingostomy)
│   └── Age ≥35, severe disease, poor ovarian reserve → IVF
│
└── HYDROSALPINX
    ├── Salpingectomy (preferred) or tubal occlusion
    └── Then proceed to IVF

Special Situations

• Berek & Novak's Gynecology, pp. 2060–2062 (Treatment of Tubal Factor Infertility — Proximal Tubal Occlusion, Distal Tubal Occlusion, Hydrosalpinx, Sterilization Reversal)
• Berek & Novak's Gynecology, p. 2060 (Falloposcopy, Selective Salpingography)
• ESHRE Guidelines on Unexplained Infertility (HSG vs. HyCoSy; CAT screening)