Multibranch anastomotic variant of the Lateral Femoral Cutaneous Nerve: possible implications in neurosurgical practice

Abstract

Dear Editor, The anatomy and topography of the lateral femoral cutaneous (LFCN) and genitofemoral (GFN) nerves is known to have some variability [6]. Their formation and distribution may complicate the outcome of several surgical procedures, such as extraperitoneal approaches to the anterior and lateral lumbar spine [1, 2], rendering these nerves more vulnerable to iatrogenic injury. During a routine dissection of a formalin-fixed, 78-yearold male cadaver, a variant left LFCN was encountered. In the pelvis, the LFCN originated from the L2/L3 roots and emerged typically from the lateral border of the psoas major (PM) muscle. The nerve gave off a lateral accessory LFCN and a medial accessory anterior femoral cutaneous nerve branch, at 5.6 cm and 7.2 cm from the lateral border of the PM muscle, respectively. The GFN, after penetrating the PM muscle, branched off at 3.4 cm prior to the inguinal ligament (IL), providing a lateral nerve that anastomosed with the two LFCN branches below the IL level (Fig. 1a). The three nerve branches passed separately behind the IL and anastomosed 1.1 cm below the IL level, creating a multibranch octopus-like formation that eventually gave off six terminal nerve branches providing sensory supply to the anterolateral thigh (Fig. 1b). Both GFN and LFCN constitute branches of the lumbar plexus [6]. In GFN neuropathy, the symptomatology includes sensory loss and paresthesia over the GFN distribution area. In our case, the GFN anastomosed with the LFCN below the IL level; thus GFN neuralgia may present with sensory abnormalities such as numbness in the anterolateral and lateral thigh. LFCN injury leads to “meralgia paresthetica”, a disorder presenting with paresthesia and numbness over the LFCN supplied area [4]. The IL constitutes a potential entrapment site; in our case, three nerve branches passed behind the IL, jeopardizing nerve traction and neuropathy, leading to increased risk of producing such symptoms. Surgical treatment of “meralgia paresthetica” mainly includes nerve decompression or neurolysis and transposition of the trapped nerve branch [5]. Neurectomy can be also done in cases where other surgical treatments have failed [3]. The presence of multiple nerve branches passing behind the IL may provoke recurrence of symptoms if the surgeon does not identify the responsible nerve branch, although this multinerval supply may be useful in preserving sensation in the affected area after resection of the injured branch. Both LFCN and GFN can be injured during a lateral retroperitoneal approach to the lumbar spine [1, 2]. It is also challenging to recognize possible variants in surgery. Due to the fact that their activity is difficult if not impossible to be monitored reliably with neurophysiology intraoperatively, this type of injury usually remains unnoticed during surgery, with patients complaining for thigh numbness postoperatively [2]. Fortunately, the symptoms tend to resolve within weeks. G. K. Paraskevas :K. Natsis :M. Tzika Department of Anatomy, Faculty of Medicine, Aristotle University, Thessaloniki, Greece