Meralgia paresthetica

Meralgia paresthetica is a neuropathic condition caused by compression of the lateral femoral cutaneous nerve. It results in tingling, numbness, and burning pain on the outer thigh. Early recognition is important to prevent chronic discomfort and functional limitation.

Anatomy and Pathophysiology

Lateral Femoral Cutaneous Nerve (LFCN)

The lateral femoral cutaneous nerve is a purely sensory nerve originating from the lumbar plexus, typically from the L2 and L3 nerve roots. It travels along the lateral border of the psoas major, crosses the iliacus muscle, and passes under or through the inguinal ligament near the anterior superior iliac spine. The nerve provides sensory innervation to the anterolateral aspect of the thigh. Anatomical variations in its course are common and can predispose it to entrapment.

Mechanism of Nerve Compression

Meralgia paresthetica arises from entrapment or compression of the lateral femoral cutaneous nerve along its course, particularly as it passes under the inguinal ligament. Compression leads to ischemia and altered nerve conduction, producing sensory symptoms. Factors such as increased intra-abdominal pressure, obesity, tight clothing, or prolonged standing can exacerbate nerve compression. Chronic entrapment may result in demyelination or axonal injury, affecting the quality and duration of symptoms.

Etiology and Risk Factors

Meralgia paresthetica can result from a variety of mechanical, metabolic, and systemic factors that increase pressure on the lateral femoral cutaneous nerve. Understanding these causes helps guide prevention and management strategies.

• External Compression: Tight belts, corsets, or clothing that compress the inguinal region.
• Obesity and Weight Gain: Increased abdominal girth can elevate pressure on the nerve under the inguinal ligament.
• Pregnancy: Hormonal changes and increased intra-abdominal pressure can lead to transient nerve compression.
• Trauma and Surgical Complications: Direct injury to the nerve during hip or pelvic surgery, fractures, or accidents.
• Metabolic and Systemic Conditions: Diabetes mellitus, hypothyroidism, and other systemic conditions can predispose to nerve dysfunction.

Clinical Presentation

The hallmark features of meralgia paresthetica involve sensory disturbances along the lateral thigh. Symptoms can vary in intensity and may affect daily activities.

• Symptoms: Tingling, burning, numbness, and occasional sharp pain on the outer thigh.
• Distribution: Sensory changes are limited to the area innervated by the lateral femoral cutaneous nerve, sparing the groin and medial thigh.
• Aggravating Factors: Prolonged standing, walking, or sitting with crossed legs.
• Relieving Factors: Removing tight clothing, lying down, or changing posture.
• Impact on Daily Life: Discomfort may interfere with walking, exercise, or sitting for extended periods.

Diagnostic Evaluation

Clinical Examination

Diagnosis of meralgia paresthetica is primarily clinical, based on history and physical examination. Key components include:

• Inspection and Palpation: Assess for tenderness near the anterior superior iliac spine and along the course of the nerve.
• Sensory Testing: Evaluate light touch, pinprick, and temperature sensation over the anterolateral thigh.
• Provocative Maneuvers: Maneuvers such as hip extension or prolonged standing may reproduce symptoms.

Imaging Studies

Imaging is used to rule out alternative causes of thigh pain and to evaluate the nerve in complex cases:

• Ultrasound: Visualizes the lateral femoral cutaneous nerve and detects entrapment or compression.
• MRI and CT: Useful for identifying masses, hernias, or pelvic lesions compressing the nerve.

Electrodiagnostic Tests

Electrodiagnostic studies can support the diagnosis when clinical findings are inconclusive:

• Nerve Conduction Studies: Assess conduction velocity and detect slowing or block along the lateral femoral cutaneous nerve.
• Electromyography (EMG): Helps rule out lumbar radiculopathy or other peripheral neuropathies affecting the thigh.

Differential Diagnosis

Several conditions can mimic meralgia paresthetica and should be considered:

• Lumbar Radiculopathy (L2-L3): May present with similar thigh pain but often includes back pain and motor deficits.
• Hip Joint Disorders: Osteoarthritis or labral tears can cause lateral thigh discomfort.
• Peripheral Neuropathies: Diabetic or metabolic neuropathies may produce sensory changes in the lower extremities.
• Other Causes: Soft tissue tumors, hematomas, or hernias near the inguinal region may compress the nerve.

Management and Treatment

Conservative Management

Initial treatment of meralgia paresthetica is typically non-surgical and aims to relieve nerve compression and reduce symptoms.

• Activity Modification: Avoid prolonged standing, walking, or sitting with crossed legs. Remove tight clothing or belts that compress the inguinal region.
• Weight Reduction: Weight loss in overweight patients can reduce pressure on the lateral femoral cutaneous nerve.
• Physical Therapy: Stretching and strengthening exercises targeting the hip flexors and pelvic muscles can relieve nerve entrapment.
• Pharmacologic Therapy: Nonsteroidal anti-inflammatory drugs (NSAIDs) or medications for neuropathic pain, such as gabapentin or pregabalin, may be prescribed.

Interventional Therapies

When conservative measures fail, interventional approaches can provide symptom relief.

• Nerve Blocks: Local anesthetic injections around the lateral femoral cutaneous nerve can provide temporary relief and confirm diagnosis.
• Botulinum Toxin Injection: May reduce pain by decreasing local muscle spasm and nerve irritation in selected cases.

Surgical Management

Surgery is reserved for persistent or severe cases not responding to conservative or interventional therapies.

• Indications: Chronic pain, functional impairment, or confirmed nerve entrapment unresponsive to other treatments.
• Procedures: Nerve decompression or neurectomy of the lateral femoral cutaneous nerve.
• Outcomes: Surgery generally provides relief, but there is a risk of numbness or residual neuropathic pain in the thigh.

Prognosis and Complications

Meralgia paresthetica generally has a favorable prognosis, especially with early recognition and appropriate management.

• Natural Course: Symptoms may resolve spontaneously in mild cases or with lifestyle modifications.
• Factors Affecting Recovery: Duration of compression, severity of nerve injury, obesity, and adherence to treatment strategies.
• Potential Complications: Chronic neuropathic pain, persistent numbness, and, rarely, surgical complications such as infection or incomplete symptom relief.

Prevention

Preventive strategies focus on minimizing factors that contribute to compression of the lateral femoral cutaneous nerve.

• Ergonomic Measures: Avoid prolonged standing, sitting with crossed legs, or repetitive hip flexion that may compress the nerve.
• Lifestyle Modifications: Maintain a healthy weight to reduce pressure in the inguinal region.
• Clothing Choices: Avoid tight belts, corsets, or garments that constrict the waist or hips.
• Posture and Activity Awareness: Incorporate regular stretching and movement to prevent nerve entrapment during daily activities.

References

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