Meralgia paraesthetica

Signs and symptoms

Symptoms are purely sensory and typically unilateral, occurring in about 78% of cases, though bilateral involvement is possible. The most common complaint is pain, paresthesias, or dysesthesias on the anterolateral thigh extending just above the knee. These abnormal sensations include burning, tingling, numbness, stinging, hypersensitivity, and itching, with intensity ranging from mild to function-limiting. Activity and position influence symptoms; standing or prolonged hip extension may worsen them, while sitting or hip flexion often brings relief.

Causes

Meralgia paraesthetica results from compression or injury to the lateral femoral cutaneous nerve, often at or near the inguinal ligament where the nerve passes between the ilium and the ligament near the anterior superior iliac spine. Tight clothing, belts, or seat belts can compress the nerve, as can conditions that increase intra-abdominal volume such as ascites, obesity, and pregnancy. Less common causes include direct pressure from a tumor or cyst, accidental injury like seat belt trauma from a car accident, and iatrogenic injury from peri-operative positioning or surgical procedures. Strenuous physical activity may trigger symptoms in individuals with anatomic variations that predispose the nerve to compression during certain limb movements.

Diagnosis

Diagnosis is generally based on clinical examination and patient history, including sensory assessment of the affected region and comparison with the unaffected leg. A diagnostic nerve block, where anesthetic is injected near the nerve, is used to confirm lateral femoral cutaneous nerve involvement; a positive test provides symptom relief lasting 30–40 minutes.

Atypical presentations may require imaging such as lumbar MRI to rule out L2/L3 lumbar radiculopathy, or MRI/CT/x-ray to exclude mass lesions compressing the nerve. Magnetic resonance neurography can assess signal alterations along the nerve, and neurophysiological testing includes sensory nerve conduction studies or somatosensory evoked potentials. Image-guided nerve blocks help distinguish involvement of other nerves.

Treatment

Meralgia paraesthetica is often self-limiting; one study found 62% of untreated patients had complete symptom resolution after two years. Conservative measures include eliminating tight clothing and belts, weight loss, avoiding aggravating activities, and physical therapy to stretch muscles and tendons along the nerve. Medications such as NSAIDs, topical capsaicin, and lidocaine gel or patches may provide symptomatic relief. Therapeutic nerve blocks combined with corticosteroids offer variable relief, with long-term complete pain relief in about 22% of cases; the revision rate for injections is approximately 81%, often leading to repeat injection or nerve decompression.

Radiofrequency ablation is an emerging non-surgical option. Surgery is recommended when repeated nerve blocks fail; options are nerve decompression, which preserves sensation by removing compressive material, and neurectomy, which transects the nerve and causes permanent numbness distally, though patients are rarely bothered by this loss.

Did You Know?

• Meralgia paraesthetica was first described in 1885 by Martin Bernhardt and named by Vladimir Karlovich Roth in 1895.
• Roth noticed the syndrome in cavalrymen who wore their belts too tightly, leading to the alternative name Bernhardt-Roth syndrome.