Ultrasound-Guided Diagnosis and Injection of the Lateral Femoral Cutaneous Nerve with an Anatomical Variation

Abstract

Meralgia paresthetica (MP) is an entrapment neuropathy of the lateral femoral cutaneous nerve (LFCN). There are many variations in the course of the LFCN. A 55-year-old woman presented with pain and tingling sensations on the anterolateral aspect of her left thigh. Physical examination revealed hypoesthesia of the proximal anterolateral thigh on the left side. During the electrodiagnostic study, sensory nerve action potential of the LFCN could not be obtained on both sides. Through those clinical and electrophysiological findings, we prediagnosed the case as MP and planned to perform diagnostic nerve block. For the injection to perform, ultrasonography was used. During the ultrasonographic evaluation, the left LFCN was visualized lateral to the anterior superior iliac spine (ASIS). Then ultrasound-guided nerve block with 2 cc lidocaine 2% for diagnostic purpose was performed in this region. Immediately after the injection, the patient's complaints relieved completely, and hence the patient was diagnosed as having MP with an LFCN anatomical variation. Two months later her complaints persisted, and ultrasound-guided LFCN injection with 2 mL of lidocaine 2% + 1 cc of betametazone was performed. One month after the second injection, her complaints were relieved markedly and she resumed her daily activities. In conclusion, the course of the LFCN is quite variable. We present a relatively rare anatomical variation of the LFCN, crossing lateral to the ASIS, diagnosed with ultrasonography. Ultrasonography can be performed to visualize the LFCN, especially a nerve with an anatomical variation.