Abstract
Meralgia paresthetica is caused by compression of the lateral femoral cutaneous nerve by the inguinal ligament. This entrapment neuropathy manifests as pain, numbness, and dysesthesias in the distribution of the lateral femoral cutaneous nerve. The symptoms often begin as a burning pain in the lateral thigh, with associated cutaneous sensitivity. Patients suffering from meralgia paresthetica note that sitting, squatting, or wearing low-cut trousers (taille basse) wide belts causes the symptoms to worsen. Although traumatic lesions to the lateral femoral cutaneous nerve have been implicated in meralgia paresthetica, in most patients, no obvious antecedent trauma can be identified. Physical findings include tenderness over the lateral femoral cutaneous nerve at the origin of the inguinal ligament at the anterior superior iliac spine. A positive Tinel sign over the lateral femoral cutaneous nerve as it passes beneath the inguinal ligament may be present. Patients may complain of burning dysesthesias in the nerve’s distribution. Careful sensory examination of the lateral thigh reveals a sensory deficit in the distribution of the lateral femoral cutaneous nerve; no motor deficit should be present. Sitting or the wearing of low-cut trousers (taille basse), tight waistbands, or wide belts can compress the nerve and exacerbate the symptoms of meralgia paresthetica.
Keywords
meralgia paresthetics, entrapment neuropathy, lateral femoral cutaneous nerve, taille basse, Tinel sign, inguinal ligament, thigh pain, thigh numbness, diagnostic sonography, ultrasound guided injection, lateral femoeral cutaneous neuralgia, electromyography
ICD-10 CODE G57.10
The Clinical Syndrome
Meralgia paresthetica is caused by compression of the lateral femoral cutaneous nerve by the inguinal ligament. This entrapment neuropathy manifests as pain, numbness, and dysesthesias in the distribution of the lateral femoral cutaneous nerve. The symptoms often begin as a burning pain in the lateral thigh, with associated cutaneous sensitivity. Patients suffering from meralgia paresthetica note that sitting, squatting, or wearing low-cut trousers (taille basse) and/or wide belts causes the symptoms to worsen ( Fig. 102.1 ). Although traumatic lesions to the lateral femoral cutaneous nerve have been implicated in meralgia paresthetica, in most patients, no obvious antecedent trauma can be identified.
Signs and Symptoms
Physical findings include tenderness over the lateral femoral cutaneous nerve at the origin of the inguinal ligament at the anterior superior iliac spine. A positive Tinel sign over the lateral femoral cutaneous nerve as it passes beneath the inguinal ligament may be present. Patients may complain of burning dysesthesias in the nerve’s distribution ( Fig. 102.2 ). Careful sensory examination of the lateral thigh reveals a sensory deficit in the distribution of the lateral femoral cutaneous nerve; no motor deficit should be present. Sitting or the wearing of low-cut trousers (taille basse), tight waistbands, or wide belts can compress the nerve and exacerbate the symptoms of meralgia paresthetica.
Testing
Electromyography (EMG) can distinguish lumbar radiculopathy and diabetic femoral neuropathy from meralgia paresthetica. Plain radiographs of the back, hip, and pelvis are indicated in all patients who present with meralgia paresthetica, to rule out occult bony disease. Based on the patient’s clinical presentation, additional testing may be warranted, including a complete blood count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging (MRI) and ultrasound imaging of the back are indicated if a herniated disk, spinal stenosis, or space-occupying lesion is suspected. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.
Differential Diagnosis
Meralgia paresthetica is often misdiagnosed as lumbar radiculopathy, trochanteric bursitis, or primary hip disease. Radiographs of the hip and EMG can distinguish meralgia paresthetica from radiculopathy or pain emanating from the hip. In addition, most patients suffering from lumbar radiculopathy have back pain associated with reflex, motor, and sensory changes, whereas patients with meralgia paresthetica have no back pain and no motor or reflex changes; the sensory changes of meralgia paresthetica are limited to the distribution of the lateral femoral cutaneous nerve and should not extend below the knee. Lumbar radiculopathy and lateral femoral cutaneous nerve entrapment may coexist as the double-crush syndrome. Occasionally, diabetic femoral neuropathy produces anterior thigh pain, which may confuse the diagnosis.
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