What is the diagnosis and treatment for a patient complaining of numbness and burning sensation in the right thigh for 2 months triggered by prolonged sitting?

Meralgia Paresthetica: Diagnosis and Management

This patient has meralgia paresthetica, an entrapment neuropathy of the lateral femoral cutaneous nerve, and should be managed initially with conservative measures including weight loss (if obese), avoiding tight clothing and prolonged standing, with consideration of local anesthetic/corticosteroid injection if symptoms persist beyond 4-6 weeks. 1, 2

Clinical Diagnosis

The presentation of numbness and burning sensation in the right thigh triggered by prolonged sitting is pathognomonic for meralgia paresthetica. Key diagnostic features include:

• Unilateral symptoms affecting the anterolateral thigh (not bilateral or distal extremities) 1, 2
• Purely sensory complaints: paresthesia, numbness, burning, dysesthesia without motor weakness 2, 3
• Positional triggers: worsened by prolonged standing, walking, or sitting; improved with lying down 4, 3
• Normal reflexes: distinguishes this from diabetic polyneuropathy which presents with reduced ankle reflexes and bilateral stocking-glove distribution 1

The lateral femoral cutaneous nerve arises from L2-L3 roots and becomes entrapped at the inguinal ligament near the anterior superior iliac spine. 2 Common precipitating factors include obesity, tight clothing/belts, prolonged standing, pregnancy, or increased intra-abdominal pressure. 2, 3

Diagnostic Confirmation

While diagnosis is primarily clinical, ultrasound imaging has emerged as the preferred confirmatory test:

• Ultrasound shows hypoechoic and swollen lateral femoral cutaneous nerve at the entrapment site and can identify underlying causes 2
• Nerve conduction studies are not routinely recommended in daily practice despite being mentioned in literature 2
• Red flag exclusion: Rule out pelvic/retroperitoneal tumors, lumbar disk herniation, or other serious pathology through history and imaging if atypical features present 5, 3

Treatment Algorithm

First-Line Conservative Management (Success Rate 91%)

Conservative treatment successfully relieves symptoms in 91% of patients and should be maintained for at least 4-6 weeks: 5, 3

• Eliminate mechanical factors: Remove tight belts, avoid restrictive clothing 4, 3
• Limit prolonged standing and sitting: Modify activities that provoke symptoms 4, 3
• Weight loss: Essential for obese patients 4, 3
• Abdominal muscle strengthening: Reduces nerve stretch 2

Second-Line: Injection Therapy

If conservative measures fail after 4-6 weeks, proceed to:

• Local anesthetic plus corticosteroid injection at the entrapment site (near anterior superior iliac spine) 4
• Ultrasound guidance improves accuracy and provides immediate interventional capability 2

Third-Line: Neuropathic Pain Medications

For persistent burning pain despite above measures:

• Gabapentin or pregabalin may provide symptomatic relief, though side effects (somnolence) limit tolerability 1, 6
• Duloxetine is an alternative option 1

Fourth-Line: Advanced Interventions (Refractory Cases Only)

Only 9% of patients require surgical intervention after failed conservative management: 5

• Peripheral nerve stimulation (PNS): Newer minimally invasive option providing sustained pain relief (>12 months documented) 6
• Surgical nerve sectioning: Success rate 96% (23/24 patients), preferred over neurolysis with transposition due to anatomical variations and neurinoma formation 5
• Neurolysis with transposition has higher recurrence rates 5

Critical Pitfalls to Avoid

• Do not confuse with diabetic neuropathy: Diabetic polyneuropathy presents bilaterally in stocking-glove distribution with reduced reflexes, not unilateral thigh symptoms with normal reflexes 1
• Do not rush to surgery: 91% respond to conservative management; surgical intervention should only occur after exhausting all nonoperative therapies 5, 3
• Do not miss serious pathology: One patient in a surgical series had early relief but later developed symptoms from undetected pelvic neoplasm 5
• Pregnancy-related cases: Usually self-limiting and resolve within 1 week postpartum with conservative management 4