Meralgia Paresthetica – Lateral Femoral Cutaneous Neuropathy

Posted by Chris Faubel, MD

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Courtesy the ‘Mayo Foundation’

Meralgia paresthetica is a mononeuropathy of the lateral femoral cutaneous nerve (LFCN), most commonly caused by entrapment as it passes underneath the inguinal ligament.

Lateral femoral cutaneous nerve

  • Pure sensory nerve
  • Formed by the ventral rami of the L2 and L3 nerve roots
  • Runs in the retroperitoneal space along the lateral border of the iliacus muscle, and then passes under the lateral aspect of the inguinal ligament about 1-cm medial to the anterior superior iliac spine (ASIS).
  • Supplies sensation to the anterolateral thigh (more lateral than anterior) – see image
  • ICD-9 code: 355.1 “meralgia paresthetica”
  • ICD-10 code: G57.1 “meralgia paresthetica” (lateral cutaneous nerve of thigh syndrome)

History

  • Patients typically complain of paresthesias (abnormal sensations – burning, tingling) and numbness in the anterolateral thigh
    • Hyperesthesias and dysesthesias possible
    • Patients normally say, “thigh numbness” or “thigh tingling
  • May be mild to severe pain
  • Unilateral, but can be bilateral in 20% of cases
  • Walking and standing (hip extension movements) can make worse

Physical exam

  • Numbness may be noted over the anterolateral thigh
  • Tapping over the lateral femoral cutaneous nerve as it passes under the inguinal ligament just medial to the ASIS may reproduce the symptoms (with the patient in a femoral nerve stretch position)
  • Pelvic Compression Test (see photo below)
    • With patient in side-lying position, press downward and slightly forward, in a manner to slacken the inguinal ligament – hold for 45 seconds
    • Resolution or reduction in symptoms is considered positive for meralgia paresthetica
    • This should also help differentiate the symptoms anterior thigh symptoms from upper lumbar radiculopathy
    • Sensitivity of 95% and a specificity of 93.3% for meralgia paresthetica (abstract here)

Causes

  • Anything that causes compression of the LFCN at the lateral inguinal ligament
  • Examples: Obesity (abdominal pannus), pregnancy, tight clothing (women in tight, low-rise jeans), leaning against table for hours while working, tool belts, policemen belts, body armor of soldiers
  • Also seen in patients with recent weight loss
  • Diabetes – as with most neuropathies
  • Rare causes:  neoplasms, hematomas, other masses in retroperitoneal space

Differential Diagnoses

  • Femoral neuropathy, upper lumbar radiculopathy (L2/3)

Workup

  • May perform nerve conduction studies (comparing both sides) of the lateral femoral cutaneous nerve, and needle electromyography (to rule out radiculopathy)

Treatment

  • #1: Avoidance of aggravating activity / cause of the compression
    • Weight loss, work station adjustment, loose jeans
  • Medications
    • Neuropathic pain medications are rarely helpful
    • NSAIDs for 7-10 days
    • Lidoderm patches – if significant dysesthesias
  • Injections

Learn about the lateral femoral cutaneous nerve steroid injection technique and tips HERE.

  • Surgery
    • Decompression or resection of the nerve by an orthopedic surgeon may be needed in extreme cases

Prognosis

  • Paresthesias resolve over weeks to months, with some residual numbness possibly being permanent
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