A noninvasive method of neurography in meralgia paraesthetica

Abstract

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.

Utility of ultrasound‐guided surface electrode placement in lateral femoral cutaneous nerve conduction studies

“…To our knowledge, previous studies have not specifically evaluated the reliability of an LFCN nerve conduction technique in obese patients. Studies to date have either not reported the BMI of study subjects or have included very few obese patients, despite the fact that meralgia paresthetica often presents in the setting of obesity 1–5, 7, 8, 15, 18, 19…”

“…Attempts to establish a reliable technique for accurate sensory nerve conduction study (NCS) of the LFCN have been limited by poor reproducibility, high interside variability, and/or absent responses, particularly in obese subjects 2–8. Anatomic studies have shown significant variability in the proximal location of the LFCN at the level of the inguinal ligament and ASIS, as well as the distal location, where the nerve penetrates the fascia 7, 9, 10.…”

Variability in conduction of the lateral femoral cutaneous nerve

“…The nerve often is found more medial to the spine or exits the pelvis over the iliac crest 11. About 10 cm inferior to the inguinal ligament the nerve usually pierces the fascia and branches into a large anterior branch and a somewhat smaller posterior branch 2, 19. The exact point at which the nerve becomes superficial in the thigh is variable 20…”

Les syndromes canalaires des régions glutéales et de la face latérale de la hanche

“…Cependant, le nerf peut être comprimé sur tout son trajet qu'il convient d'explorer par l'imagerie si le test anesthésique est négatif. L'étude électrophysiologique n'est pas aisée car il est difficile de stimuler le nerf en amont de la zone de compression [54][55][56], mais cet examen est rarement nécessaire au diagnostic. Seule une perte axonale par rapport au côté opposé permet d'affirmer la lésion du nerf qui se situe presque toujours au niveau de l'épine iliaque antérosupé-rieure [56].…”