The lateral femoral cutaneous nerve canal

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OBJECTIVE

Meralgia paresthetica causes dysesthesias and burning in the anterolateral thigh. Surgical treatment includes nerve transection or decompression. Finding the nerve in surgery is very challenging. The author conducted a cadaveric study to better understand the variations in the anatomy of the lateral femoral cutaneous nerve (LFCN).

METHODS

Twenty embalmed cadavers were used for this study. The author studied the LFCN's relationship to different fascial planes, and the distance from the anterior superior iliac spine (ASIS).

RESULTS

A complete fascial canal was found to surround the nerve completely in all specimens. The canal starts at the inguinal ligament proximally and follows the nerve beyond its terminal branches. The nerve could be anywhere from 6.5 cm medial to the ASIS to 6 cm lateral to the ASIS. In the latter case, the nerve may lodge in a groove in the iliac crest. Other anatomical variations found were the LFCN arising from the femoral nerve, and a duplicated nerve. A thick nerve was found in 1 case in which it was riding over the ASIS.

CONCLUSIONS

The variability in the course of the LFCN can create difficulty in surgical exposure. The newly defined LFCN canal renders exposure even more challenging. This calls for high-resolution pre- or intraoperative imaging for better localization of the nerve.

ABBREVIATIONSASIS = anterior superior iliac spine; LFCN = lateral femoral cutaneous nerve.

Article Information

INCLUDE WHEN CITING Published online April 22, 2016; DOI: 10.3171/2016.1.JNS152262.

Correspondence Amgad Hanna, Department of Neurological Surgery, University of Wisconsin, 600 Highland Ave., Madison, WI 53792. email: ah2904@yahoo.com.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Specimen 17 left. A: Left LFCN riding over the iliac crest (white arrow) just lateral to the ASIS. B: Close-up view after medial retraction of the nerve. An instrument is pointing to a groove in the iliac crest (black arrow), the “supra-iliac groove.”

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    Specimen 14. A: Left anterior thigh dissection showing enlargement (arrowheads) of the LFCN (yellow loop). This nerve entered the thigh at the ASIS (arrow). B and C: Axial cut reveals thickened perineurium (arrows) and Renaut bodies (arrowheads). Trichrome stain, bar = 1 mm.

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    A and B: Specimen 19 left. A: The LFCN (arrowheads) was found 6.5 cm medial to the ASIS (arrow). B: Followed in the retroperitoneum, the nerve originated from the femoral nerve. C: In a fresh postmortem specimen, the left LFCN (1) was found originating with 2 components, one directly from the lumbar plexus, and the other from the femoral nerve (2). The ilioinguinal nerve (3) is seen proximal to the LFCN. A = femoral artery; F = femoral nerve.

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    Specimen 13. Left anterior thigh dissection revealing 2 LFCNs. One LFCN (black arrow) is 7 mm lateral to the ASIS (red pin), and the other (black arrowhead) is 5 cm medial to the ASIS. Note the femoral nerve (white arrow) medial to the LFCN.

  • View in gallery

    Left LFCN and its branches (red loops) after unroofing the LFCN canal. A: The nerve is lifted up to reveal the posterior wall of the LFCN canal (arrow). B: A Freer elevator is used to demonstrate the deep fascial layer separating the nerve from the muscle.

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    Oblique axial cut of the left thigh caudal to the ASIS, showing the LFCN in its individual canal. A: White arrow = LFCN in its own canal; single white arrowhead = femoral nerve; double arrowheads = sciatic nerve; black arrow = obturator nerve (posterior division); black arrowhead = obturator nerve (anterior division); AB = adductor brevis; AL = adductor longus; AM = adductor magnus; F = femur; G = gracilis; GM = gluteus maximus; HAM = hamstrings; IP = iliopsoas; P = pectineus; RF = rectus femoris; S = sartorius; TFL = tensor fasciae latae. B: Close-up view, with the white arrow pointing to the LFCN in its individual canal. C: Close-up view, with 2 forceps holding the anterior and posterior layers of the LFCN canal. D: Diagrammatic representation of the left LFCN canal in an axial cut. 1 = skin; 2 = subcutaneous tissue; 3 = fascia lata; 4 = tensor fasciae latae; 5 = femur; 6 = iliopsoas; 7 = adductor magnus; 8 = pectineus; 9 = femoral sheath; 10 = femoral canal; 11 = femoral vein; 12 = femoral artery; 13 = femoral branch of genitofemoral nerve; 14 = femoral nerve; 15 = rectus femoris; 16 = sartorius; 17 = LFCN canal; 18 = LFCN. Copyright Amgad Hanna (Panel D). Published with permission.

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    A: Transverse ultrasound revealing the left LFCN (arrow) in its individual canal. B: Longitudinal ultrasound revealing the left LFCN (arrow) within the LFCN canal (arrowheads).

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    A: Diagrammatic representation of the LFCN canal in an oblique sagittal view at the level of the anterior inferior iliac spine. 1 = skin; 2 = subcutaneous tissue; 3 = external oblique muscle and aponeurosis; 4 = internal oblique; 5 = transversus abdominis; 6 = transversalis fascia; 7 = fascia iliaca superficial lamina; 8 = retroperitoneal fat; 9 = LFCN; 10 = fascia iliaca deep lamina; 11 = iliacus; 12 = iliac bone; 13 = femur; 14 = rectus femoris; 15 = sartorius; 16 = fascia lata; 17 = LFCN canal; 18 = inguinal ligament; 19 = iliopubic tract; 20 = thickening of the fascia deep to the LFCN (here by the tendinous origin of the sartorius; can also be a slip from the inguinal ligament, or periosteum if the nerve is riding over the ASIS or iliac crest). B: Axial section through the retroperitoneal segment of the LFCN. 1 = anterior lamina of fascia iliaca; 2 = LFCN; 3 = retroperitoneal fat; 4 = posterior lamina of fascia iliaca; 5 = iliacus muscle. C: Axial section through the floor of the LFCN canal (arrowheads), showing a thick layer separating the nerve from the muscle in the region of the inguinal ligament. Trichrome stain (B and C), no magnification (B). Copyright Amgad Hanna (Panel A). Published with permission.

  • View in gallery

    Axial section approximately 4 cm distal to the ASIS showing the LFCN (arrow) and its branches (arrowheads) within the LFCN canal. With van Gieson stain, elastic fibers are black and collagen is red; with trichrome stain, collagen is blue and nuclei are purple. 1 = fascia superficial to the LFCN; 2 = fascia deep to the LFCN; 3 = lymph node; 4 = vein; 5 = muscle. Note that the fascia superficial to the nerve is thicker than the one deep to it. The 2 fasciae get closer to each other and become thicker on either side of the nerve. The fat content of the LFCN canal is much less than in the retroperitoneal space (Fig. 8B), thus significantly limiting the nerve's mobility in the thigh. Elastic van Gieson (A and C) and trichrome (B and D), no magnification (A and B).

  • View in gallery

    A: Wrong concept illustrating a single layer of fascia superficial to the LFCN. Based on this, opening the fascia in any location will allow access to the nerve (green arrows). B: Correct concept illustrating the LFCN canal with its 2 components superficial and deep to the nerve. Based on this, opening the fascia on top of the nerve is the only way to find the nerve (green arrow). Opening on either side of the nerve canal (red arrows), not only will miss the nerve but also will make the search for the nerve extremely difficult because the second deeper layer is still intact and shields the nerve from the surgeon's eyes. Copyright Amgad Hanna. Published with permission.

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