A noninvasive method of neurography in meralgia paraesthetica

The lateral femoral cutaneous nerve (LFCN) becomes superficial 10 cm distal to the anterior superior iliac spine, where it can be located and stimulated by superficial electrodes. This is not the case in the inguinal region. In the present study the LFCN compound nerve action potential (NAP) was recorded with a pair of 8-cm-long strip electrodes placed on the anterolateral aspect of the thigh 25 cm distal to the stimulating electrodes. Normative values were obtained in 58 healthy nerves. The conduction velocity (CV) was 62.3 +/- 5.5 m/s for NAP onset and 55.3 +/- 4.1 m/s for the negative NAP peak. The CV variability was comparable to that obtained with needle recordings despite a relatively low NAP amplitude (2.0 +/- 1.0 muV). This method provided definite neurophysiological evidence of the disorder in 12 of 13 patients with meralgia paraesthetica. According to our results, a slowing of CV is a more reliable sign of the condition than a decrease of NAP amplitude alone.