What is lateral cutaneous nerve of thigh syndrome (meralgia paresthetica)?

Lateral Cutaneous Nerve of Thigh Syndrome (Meralgia Paresthetica)

Definition and Clinical Presentation

Meralgia paresthetica is an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN) characterized by burning pain, tingling, numbness, and dysesthesia in the anterolateral aspect of the thigh, with preserved motor function and reflexes. 1, 2, 3

The condition presents with:

• Burning sensation, tingling, and numbness localized to the anterolateral thigh in the L2-L3 dermatome distribution 4, 2, 5
• Hypersensitivity or hyposensitivity in the affected area 5
• Normal motor strength (particularly preserved hip flexion) and intact deep tendon reflexes, distinguishing it from L2-L3 radiculopathy 4, 3
• No involvement of medial thigh or knee (which would suggest L4 nerve root pathology) 4

Etiology and Risk Factors

The LFCN becomes entrapped or compressed, typically where it passes near the inguinal ligament. Common causes include:

• Obesity and weight gain 3, 5
• Tight clothing, particularly low-cut trousers ("taille basse") or belts 5
• Diabetes mellitus 3
• Pregnancy 1
• Iatrogenic causes: complications of hip or lumbar spine surgery 3
• Abdominopelvic masses (rare but important to exclude) 2

Diagnostic Approach

The diagnosis is primarily clinical, based on the characteristic sensory symptoms in the anterolateral thigh with normal motor examination. 1, 3

Clinical Assessment

• Sensory testing of the anterolateral thigh for pinprick, temperature, and light touch abnormalities 6
• Motor examination to confirm normal hip flexion and knee extension, ruling out radiculopathy 4
• Deep tendon reflexes should be normal 3

Confirmatory Testing

• Diagnostic nerve block: Injection of local anesthetic around the LFCN provides immediate symptom relief for several hours, confirming the diagnosis 1, 5
• Electrodiagnostic studies (sensory nerve conduction studies) have sensitivity of approximately 83% but suffer from technical limitations with low specificity 3, 5
• Imaging is indicated when motor deficits are present, multiple dermatomal involvement exists, or abdominopelvic pathology is suspected 4, 2
  • MRI of lumbosacral plexus (rated 9/9 by American College of Radiology) for suspected nerve root pathology 4
  • Abdominopelvic ultrasound or MRI if mass lesion suspected 2

Management Algorithm

First-Line Conservative Management (Most Cases Respond)

Conservative treatment successfully resolves symptoms in the majority of patients. 1, 3, 5

1. Modify causative factors:

   • Avoid tight clothing and belts 5
   • Weight reduction in obese patients 5
   • Remove or treat underlying causes (e.g., cystectomy for adnexal masses) 2

2. Neuropathic pain medications for symptomatic relief 6, 3

3. LFCN nerve block with local anesthetic and corticosteroid serves both diagnostic and therapeutic roles 1, 5

   • Provides immediate diagnostic confirmation
   • Offers therapeutic benefit with steroid injection 5

Second-Line Interventional Options (For Refractory Cases)

For patients who fail conservative management after adequate trial:

• Cryoneurolysis: Emerging evidence shows 100% immediate pain relief with sustained benefit (80% at 1 month, 60% at 3 months) with low-risk safety profile 7
• Neurolysis 3
• Neurectomy 3
• Radioablation 3

Important caveat: Most cases are self-limited, but a small proportion develop refractory, disabling symptoms requiring advanced interventions. 3 Controlled trials comparing efficacy of surgical and ablative techniques are lacking. 3

Critical Pitfall to Avoid

Do not miss L2-L3 radiculopathy or plexopathy, which can mimic meralgia paresthetica but includes motor weakness (hip flexion deficit) and may require different management. 4 The presence of motor deficits mandates imaging with MRI of the lumbosacral plexus and electrodiagnostic studies to differentiate radiculopathy from isolated LFCN entrapment. 4