What is the diagnosis and treatment for a patient with reduced pinprick sensation on the anterior lateral thigh and burning discomfort with tapping over the lateral aspect of the inguinal (groin area) canal?

Meralgia Paresthetica

Diagnosis

The clinical presentation of reduced pinprick sensation on the anterior lateral thigh with burning discomfort elicited by tapping over the lateral aspect of the inguinal canal is diagnostic of meralgia paresthetica, an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN). 1, 2

Key Diagnostic Features

• Sensory examination: Reduced pinprick sensation specifically over the anterolateral thigh in the distribution of the LFCN, with no motor deficits or other neurological abnormalities in the leg 1, 2

• Tinel's sign: Positive tapping test over the LFCN at the inguinal ligament region, reproducing burning pain or paresthesias 3

• Symptom pattern: Pain, dysesthesias (burning, tingling), and numbness confined to the anterolateral thigh that typically worsens with standing or walking 1, 4, 3

• Anatomic localization: The LFCN is most commonly entrapped at the anterior superior iliac spine or during its passage through/under the inguinal ligament 5

Diagnostic Confirmation

• Clinical diagnosis: The diagnosis is made clinically based on characteristic location of symptoms, sensory abnormality on examination, and absence of other neurological findings 1

• Diagnostic nerve block: LFCN block at the trigger point in the inguinal ligament region that provides temporary symptom relief confirms the diagnosis 3

• Imaging is not routinely required unless atypical features suggest alternative diagnoses such as hip pathology, lumbar radiculopathy, or intra-abdominal/pelvic masses 6

Treatment Algorithm

Step 1: Conservative Management (First-Line)

Conservative treatment should be initiated first, as the majority of patients with meralgia paresthetica respond well to non-invasive measures. 1, 5

• Activity modification: Limit prolonged standing and avoid tight clothing, belts, or anything that compresses the inguinal region 5

• Weight loss: Essential for obese patients, as obesity is a significant risk factor 5

• Pharmacologic management for neuropathic pain:

  • First-line: Tricyclic antidepressants (nortriptyline or desipramine starting at low doses) or SNRIs (duloxetine, venlafaxine) 7
  • Alternative first-line: Gabapentin or pregabalin (calcium channel α2-δ ligands) 7
  • Adequate trial requires 6-8 weeks, including 2 weeks at the highest tolerated dose 7

Step 2: Interventional Treatment

If conservative management fails after an adequate trial (typically 3-6 months), proceed to LFCN blocks with local anesthetic and corticosteroids. 3, 5

• Technique: Injection of local anesthetic with corticosteroid at the site of nerve entrapment in the inguinal ligament region 3, 5

• Expected outcome: May provide short-term to intermediate relief; can be repeated if initial response is favorable 1, 3

• Limitation: Some patients experience only temporary relief requiring repeated injections 1

Step 3: Surgical Options (Refractory Cases)

For patients with intractable symptoms refractory to conservative and interventional treatments, surgical intervention should be considered. 1, 2, 3

Option A: Neurolysis (Preferred Initial Surgical Approach)

• Procedure: Microscopic neurolysis of the LFCN under local anesthesia to release the entrapped nerve 3

• Outcomes: Immediate symptom improvement with sustained relief; one case series showed VAS reduction from 7.1 to 1.9 at 3 months 3

• Advantage: Preserves the nerve while relieving compression 3

Option B: Neurectomy

• Indication: When neurolysis fails or is not feasible 2

• Histopathologic findings: Moderate loss of myelinated axons, axonal atrophy, regeneration clusters, and perineurial thickening correlate with preoperative pain and paresthesias 2

• Outcome: Successful treatment of symptoms in refractory cases 2

Option C: Spinal Cord Stimulation (Last Resort)

• Indication: Intractable meralgia paresthetica when all other treatments have failed 1, 4

• Technique: Epidural paddle lead placement targeting the L2 and L3 dorsal root entry zones (DREZs) where LFCN afferents enter the spinal cord 4

• Advantages: Non-destructive, reversible (can be explanted), and provides sustained pain relief 1, 4

• Outcomes: Case reports demonstrate 100% pain relief, cessation of opioids, and return to full activity 1, 4

Critical Pitfalls to Avoid

• Do not miss alternative diagnoses: Hip pathology (osteoarthritis, labral tears, occult fractures) commonly presents with groin pain and requires plain radiographs as first-line imaging 6

• Do not confuse with lumbar radiculopathy: Meralgia paresthetica is purely sensory with no motor deficits, reflex changes, or back pain; L2-L3 radiculopathy would include hip flexor weakness 1

• Do not delay surgical referral indefinitely: Prolonged nerve compression leads to axonal degeneration and may result in irreversible changes 2

• Do not overlook secondary causes: In pregnant women, symptoms often resolve spontaneously postpartum; in obese patients, weight loss is essential 5

• Do not use inadequate medication trials: Neuropathic pain medications require 6-8 weeks at therapeutic doses before declaring treatment failure 7