Introduction

Based on the embryological branching of the spinal nerve, the primaxial muscle innervates the back and proximal body wall muscles. The superficial extramural branch supplies the abaxial muscles within the body wall, and the deep intramural branch innervates the abaxial muscles located outside the body wall. The ventral rami of the spinal nerve form the plexus, but the dorsal rami maintain the segmental pattern (1).

The lumbar plexus is present within the substance of the psoas major muscle. The second to fourth lumbar ventral rami are divided into anterior and posterior divisions. The genitofemoral nerve is formed by the union of the caudal branch of the first lumbar ventral ramus with the anterior division of the second lumbar ventral ramus. Branches from the posterior divisions of the second and third lumbar rami unite to form the lateral femoral cutaneous nerve (lateral cutaneous nerve of the thigh) (2, 3).

The genitofemoral nerve is included in the border nerves that innervate the skin that borders the thigh and abdomen. In border pain syndrome, pain radiates along its course and distribution (4-6). Compression or entrapment of the lateral femoral cutaneous nerve may cause a neurological condition called meralgia paraesthetica, which results in a burning sensation or numbness on the lateral side of the thigh (7).

Most lumbar plexus anatomical variations are well documented (2, 3, 8, 9). The objective of this study is to determine whether the level of origin, branching pattern, and exit of the lateral femoral cutaneous and genitofemoral nerves differ from those of other studies that have been published. Determine whether these nerves are absent or if any accessory nerves are present, as well as the intraabdominal course and relations of the branches of the genitofemoral nerve, which have not been described in any literature.

Materials and Methods

A total of twenty-four lateral femoral cutaneous, and genitofemoral nerves of the lumbar plexus were dissected, six of which were male and six of which were female. The level of origin, branching, and exits in relation to the psoas major muscle were carefully examined. Also determined the unique origin, intraabdominal course, relations, and branches of the genital and femoral branches. All these observations were recorded through photography. In this study, sexual dimorphism was not taken into consideration due to the small sample size. The percentage of normal and variations in origin, exits, and branching of both nerves were calculated and presented in Tables 1 and 2.

This study was conducted in the Anatomy Department of King Khalid University, Abha, Saudi Arabia, and approved by the Research Ethics Committee (ECM #2023-3325) of King Khalid University.

Results

Genitofemoral nerve

In 16 cases (66.67%), we found the genitofemoral nerve originates as a single trunk from L2 with a normal branching pattern. It divides above or near the inguinal ligament into genital and femoral branches (Figs. 1 and 5). All these nerves exit and descend along the medial border of the psoas major muscle, reaching the anterior surface of the psoas major muscle.

The other 4 cases (16.67%) of the genitofemoral nerve originate as a single trunk from L3 and show variations in branching. These exit at the medial border of the psoas major. Then it descends along the anterior surface of it and divides into genital and femoral branches at the level of L5 (Fig. 2). This genital branch is divided into two branches, enters the inguinal canal, and finally reaches the medial side of the thigh and adjacent parts of the inguinal and genital regions. The femoral branch descends deep into the inguinal ligament and finally reaches the lateral wall of the femoral sheath.

In 4 cases (16.67%), there was a separate origin for the genital and femoral branches. Among the four cases, in 2 cases (8.33%), the genital branch originated from the upper part of the medial margin of L1 and has four branches (Fig. 3). But in the other 2 cases (8.33%), the genital branch originated from L2, and it has three branches (Fig. 4). In 4 cases (16.67%), all branches descend along the medial border of the psoas muscle and superficially cross the external iliac artery. Then its lateral branches descend superficially to the external iliac artery, and its medial branches descend along the medial side of the external iliac artery (Figs.3 and 4). Finally, its lateral branches reach the anterior and lateral walls of the femoral sheath, but its medial branches reach the medial wall of the femoral sheath, the medial side of the thigh, and adjacent parts of the inguinal and genital areas (Figs.3 and 4).

The femoral branch begins as two twigs from L3 in 4 cases (16.67%) of separate origin, and these two twigs unite to form a single femoral branch (Figs.3 and 4). It descends along the lateral border of the psoas major and minor muscles and lies on the anterior surfaces of the psoas major muscle. In 2 cases (8.33%), the femoral branch is located between the two lateral femoral cutaneous nerves. It then crosses the accessory lateral femoral cutaneous nerve, passes deep into the inguinal ligament, and finally reaches the lateral wall of the femoral sheath (Fig. 3).

Lateral femoral cutaneous nerve

Of the 24 cases, 18 cases (75%) had single lateral femoral cutaneous nerves with the absence of branches (Figs. 1, 2 and 4). Out of the 18 cases of a single lateral femoral cutaneous nerve, the nerve originates from L3 in 16 cases (66.67%). But in the other 2 cases (8.33%), it originates from L2. In all 24 cases, it exits from the lateral border of the psoas major muscle.

In 4 cases (16.67%), in the intraabdominal course, the nerve divides into anterior (medial) and posterior (lateral) branches and originates from L3. Its anterior (medial) branch passes behind the femoral branch of the genitofemoral nerve and descends along the lateral wall of the femoral sheath. But its posterior (lateral) branch enters the transverse abdominis muscle near the anterior superior iliac spine (Fig. 5).

In 2 cases (8.33%), accessory nerves were found. The lateral femoral cutaneous and accessory nerves were separately originated from the upper and lower parts of the L2 (Fig. 3.). The femoral branch of the genitofemoral nerve descends anterior to the accessory lateral femoral cutaneous nerve. Both lateral femoral cutaneous nerves reach the anterior superior iliac spine (Fig. 3).

Fig 1: Representative images show that the genitofemoral nerve (GF) is divided into genital (GFG) and femoral (GFF) branches at the normal level. Lateral femoral cutaneous nerve (LFCN) with the absence of branches. PM: Psoas major muscle; PMI: Psoas minor muscle; QL: Quadratus lumborum muscle.

Fig 2: Representative images show that the genitofemoral nerve (GF) is divided into genital (GFG) and femoral (GFF) branches at L5 level. 1 and 2: branches of the genital branch of the genitofemoral nerve. Lateral femoral cutaneous nerve (LFCN) with the absence of branches. PM: Psoas major muscle; QL: Quadratus lumborum muscle.

Fig 3: Representative images show the separate origins of the genital (GFG) and femoral (GFF) branches of the genitofemoral nerve (GF). 1, 2, 3, and 4: branches of the genital branch of the genitofemoral nerve. a and b: Femoral branch of the genitofemoral nerve (GFF) originates as twigs. LFCN: Lateral femoral cutaneous nerve; ALFCN: Accessory lateral femoral cutaneous nerve; PM: Psoas major muscle; EIA: External iliac artery.

Fig 4: Representative images show the separate origins of the genital (GFG) and femoral (GFF) branches of the genitofemoral nerve (GF). 1, 2 and 3: branches of the genital branch of the genitofemoral nerve. a and b: Femoral branch of the genitofemoral nerve (GFF) originates as twigs. LFCN: Lateral femoral cutaneous nerve; PM: Psoas major muscle; EIA: External iliac artery.

Fig 5: Representative images show that the genitofemoral nerve (GF) is divided into genital (GFG) and femoral (GFF) branches at the normal level. 1 and 2: branches of the lateral femoral cutaneous nerve (LFCN). PM: Psoas major muscle; PMI: Psoas minor muscle.

Discussion:

Genitofemoral nerve

In embryological classification, the L2 spinal nerve gives rise to extramural femoral and intramural genital branches (1).

The genitofemoral nerve originates from the L1 and L2 ventral rami. Single trunk of nerve origin from L1, L2, or L3 (3, 10, 11). In the present study, 20 cases (83.33%) had the single trunk of the genitofemoral nerve. 16 cases (66.67%) and 4 cases (16.67%) of the 20 cases came from L2 and L3, respectively. The single trunk of the genitofemoral nerve was observed in 80% of the reported study (3). Its origin was found to be L2 in 4% and 99.25% of the studies (12, 3) and L3 in 0.75% of the study (3).

The femoral branch is composed of L1 fibres, but L2 fibres pass through the genital branch (13). The two separate branches observed in 20% of cases originate from L1 and L2, or L1, L2, and L3 (3). In our study, 4 cases (16.67%) observed the separate origin of genital and femoral branches. In all these cases, femoral branches originate from L3 as two twigs; later, these twigs join to form a single femoral branch. In 2 cases (8.33%), the genital branch originates from L1, and in the other 2 cases (8.33%) from L2.

The terminal divisions of the genitofemoral nerve occur at various levels (10, 11, 14), and 47.1% of variations in branching were reported (15). In 4 cases (16.67%) of the present study, branching occurs at the level of L5 on the anterior surface of the psoas major muscle. The branching occurs within the substance of the psoas major muscles (26.5%), on the upper part of its anterior surface (20.6%), and before its exit (8.3%) (3, 16).

The single trunk and genital branches of separate origin emerged from the medial border, and the femoral branch of separate origin emerged from the lateral border of the psoas major muscle. In this study, we did not notice any single trunk or branches of separate origin piercing the psoas major muscle.

The genital branch crosses superficially to the lower part of the external iliac artery above the origin of the inferior epigastric artery (3, 17-20). The same findings were observed in the single trunk genitofemoral nerve's usual branching pattern. But in cases of separate origin, there are three or four genital branches, and all these superficially cross the external iliac artery. Its lateral branches descend superficially to the external iliac artery, while its medial branches descend along the medial side of the external iliac artery. Finally, its lateral branches reach the anterior and lateral walls of the femoral sheath, while its medial branches reach the medial wall of the femoral sheath, the medial side of the thigh, and adjacent parts of the inguinal and genital areas. This type of branching pattern of the genital branch and its relation to the external iliac artery have not been seen in any reported data.

In the single trunk origin of the genitofemoral nerve, the current study found the same things as previously published studies (3, 21): the femoral branch descends lateral to the external iliac artery before crossing the deep circumflex iliac artery. In the present study, the femoral branch is located between the two lateral femoral cutaneous nerves in two cases of separate origin. It descends anterior to the accessory lateral femoral cutaneous nerve and then reaches the medial side of it. In all cases of separate origin, the femoral branch crosses the deep circumflex iliac artery before reaching the lateral side of the external iliac artery. After that, it passes deep into the inguinal ligament and then reaches the lateral wall of the femoral sheath.

Lateral femoral cutaneous nerve

Embryologically the lateral femoral cutaneous nerve is the extramural branch of L1 and L2 (1). In 2 cases (8.33%) of the present study, the single lateral femoral cutaneous nerve (LFCN) with the absence of branches originated from L2, while other authors (7, 16, 22.) reported 1.7%, 4%, and 6%, respectively. In a single nerve case, 16 cases (66.67%) with the absence of branches and 4 cases (16.67%) with branches originated from L3; the percentages of occurrence were reported in other studies (7, 16, 22) of 2.9%, 6%, and 10%, respectively.

Usually, the femoral segment of the lateral femoral cutaneous nerve divides into anterior and posterior branches. Several authors reported (15, 23-25) that this nerve bifurcated into branches in its intraabdominal segment in 2.9%, 3.5%, 23%, and 27.6% of cases, respectively. In the current study, it was early divided into anterior and posterior branches in 4 cases (16.67%). Its anterior branch passes behind the femoral branch of the genitofemoral nerve and descends along the lateral wall of the femoral sheath. Near the anterior superior iliac spine, its posterior branch enters the transverse abdominis muscle.

Accessory nerves were reported in 2.5%, 4%, and 30% of cases (26-28). But in the current study, its presence was found in 2 cases (8.33%). The lateral femoral cutaneous nerve originates from upper part of the L2 while accessory lateral cutaneous nerve from the lower part of the L2. The femoral branch of the genitofemoral nerve descends anterior to the accessory lateral femoral cutaneous nerve. Finally, both lateral femoral cutaneous nerves to reach near the anterior superior iliac spine.

Conclusion

This present study found a unique intraabdominal course and branching pattern in the genital branch of the genitofemoral and accessory lateral femoral cutaneous nerves. Such knowledge of the variations in the intraabdominal segments of the genitofemoral and lateral femoral cutaneous nerves is helpful for peripheral nerve blocks, lower abdominal wall surgical procedures, and the proper clinical diagnosis of referred pain in cases of pelvic inflammatory disease and psoas abscess.

Acknowledgements: All kinds of support availed from the Department of Anatomy, College of Medicine, King Khalid University, Abha, Saudi Arabia are gratefully acknowledged.

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