What is the diagnostic approach for meralgia paresthetica?

Diagnostic Approach for Meralgia Paresthetica

Meralgia paresthetica is diagnosed primarily through clinical evaluation based on characteristic symptoms of pain, paresthesia, and numbness in the anterolateral thigh distribution, with diagnostic nerve blocks serving as both confirmatory and therapeutic tools when the diagnosis is uncertain. 1, 2

Clinical History

The diagnosis relies on identifying specific symptom patterns:

• Pain location and quality: Burning sensation, dysesthesia, numbness, and paresthesia localized to the anterolateral thigh in the distribution of the lateral femoral cutaneous nerve (LFCN) 1, 3
• Aggravating factors: Symptoms worsen with walking, prolonged standing, or hip/trunk hyperextension 3
• Relieving factors: Symptoms typically improve with sitting or hip flexion 3
• Etiological triggers: Document history of trauma, recent surgery (especially hip procedures), weight gain, tight clothing/belts, prolonged standing, or leg length discrepancies 3, 4

Physical Examination

Perform a focused neurological examination of the affected lower extremity:

• Sensory testing: Identify sensory abnormality (decreased sensation or hyperesthesia) over the anterolateral thigh in LFCN distribution 1, 5
• Motor examination: Confirm absence of motor weakness in the leg, as LFCN is purely sensory 3
• Other neurological signs: Rule out other neurological abnormalities that would suggest alternative diagnoses 5
• Palpation: Assess for tenderness at the inguinal ligament near the anterior superior iliac spine where nerve entrapment occurs 3

Diagnostic Testing

When Diagnosis is Clinically Clear

Proceed directly to treatment without additional testing, as meralgia paresthetica is primarily a clinical diagnosis. 1, 2

When Diagnosis is Uncertain

Use the following diagnostic modalities in order of preference:

1. Diagnostic Nerve Block (First-line confirmatory test)

• Perform LFCN block with local anesthetic at the inguinal ligament level 1
• Positive response (temporary symptom relief) confirms the diagnosis 1
• This serves both diagnostic and therapeutic purposes 1

2. Ultrasound Imaging (Preferred imaging modality)

• Visualize hypoechoic and swollen LFCN at the entrapment site 3
• Identify underlying structural causes of compression 3
• Provides immediate guidance for interventional procedures 3

3. Electrodiagnostic Studies (Use selectively)

• Nerve conduction studies and electromyography can confirm diagnosis but are not routinely recommended in daily clinical practice 3
• Reserve for atypical presentations or when other neuropathies need exclusion 2

4. MRI (For specific indications only)

• Order when pelvic or retroperitoneal tumors are suspected 3
• Use to exclude other structural pathology when clinical picture is atypical 2

Differential Diagnosis Considerations

Rule out these conditions that can mimic meralgia paresthetica:

• Lumbar radiculopathy: Would present with motor weakness and reflex changes 1
• Femoral neuropathy: Would include motor deficits in quadriceps 1
• Pelvic/retroperitoneal masses: Require imaging if suspected 3
• Hip joint pathology: Would have pain with hip range of motion 4

Common Diagnostic Pitfalls

• Avoid over-reliance on electrodiagnostic studies: These are not necessary for typical presentations and electromyographers often prefer not to perform them routinely 3
• Don't miss iatrogenic causes: 78% of surgical cases in one series had hip prostheses as the underlying cause 4
• Recognize bilateral presentations: While less common, bilateral meralgia paresthetica can occur and should not exclude the diagnosis 5