Distal lesion of the lateral femoral cutaneous nerve.

We report three patients with a typical clinical picture of unilateral meralgia paresthetica in whom routine nerve conduction studies were normal. However, cortical somatosensory evoked potentials were absent after lateral femoral cutaneous nerve (LFCN) stimulation on the affected side. After stimulation of the LFCN in the anterosuperior iliac spine (ASIS) region and recording the responses distal to conventional sites (20 cm from the ASIS), sensory nerve action potentials (SNAPs) were absent in the symptomatic leg, but present in the normal leg. We suggest that thigh paresthesias may be caused by a distal LFCN lesion. Eliciting this requires recording SNAPs distal to conventional sites.