Somatosensory evoked potentials for the electrodiagnosis of meralgia paresthetica

The aim of this study was to evaluate the diagnostic utility of somatosensory evoked potential (SSEP) studies of the lateral femoral cutaneous nerve (LFCN) in assessing patients with meralgia paresthetica. Twenty-one consecutive patients with unilateral meralgia paresthetica, as defined clinically (sensory impairment of lateral aspect of the thigh) and electrodiagnostically (abnormal sensory nerve conduction), and 21 control subjects were studied with two SSEP methods. SSEPs were elicited by stimulation of the LFCN below the anterior superior iliac spine (ASIS stimulation) and by cutaneous stimulation of the lateral aspect of the distal third of the thigh (thigh stimulation). Abnormalities were defined by the SSEP interside latency difference, interside amplitude ratio, or an absent response. The SSEP with ASIS stimulation had a sensitivity of 5% and a specificity of 95%, whereas with thigh stimulation it had a sensitivity of 52% and a specificity of 76%. Overall, SSEP after ASIS stimulation had no diagnostic value. Recording of the SSEP after thigh stimulation is recommended in obese patients only when sensory nerve conduction cannot be determined.