Genitofemoral nerve

At a glance

English

Genitofemoral nerve

Latin (TA2)

Nervus genitofemoralis

System

Nerve

Region

Lower limb

Side

Paired, left and right

About the genitofemoral nerve

The genitofemoral nerve arises from the ventral rami of L1 and L2, which unite within the substance of psoas major. Unlike the other branches of the lumbar plexus, which leave the borders of the muscle, it pierces psoas and appears on its anterior surface, then runs down over the front of the muscle under the peritoneum, behind the ureter. It should not be confused with the femoral nerve, a separate and much larger plexus branch.

Somewhere on psoas, usually about halfway down, the nerve splits into its genital and femoral branches. The split is variable: in a sizeable minority of people it happens higher, before the nerve reaches the front of the muscle or while it is still inside the belly of psoas, so that muscle fibres separate the two branches as they emerge.

The genital branch crosses the external iliac artery, enters the deep inguinal ring and follows the inguinal canal. It supplies the cremaster muscle and a small area of skin in the front of the groin. The femoral branch, also called the lumboinguinal nerve, runs lateral to the external iliac artery, passes under the inguinal ligament inside the lateral part of the femoral sheath and pierces the sheath or the cribriform fascia over the saphenous opening. It supplies skin over the upper femoral triangle on the front of the thigh.

Between them the two branches carry the cremasteric reflex: sensation from the skin of the upper inner thigh enters partly through the femoral branch, and the cremaster contraction is driven through the genital branch. The reflex therefore tests the L1 and L2 segments. The nerve can be damaged on the back abdominal wall during retroperitoneal or laparoscopic surgery and by a psoas abscess or appendicitis lying against it; in the groin its branches are at risk during hernia repair. Injury gives burning pain or numbness in the groin and upper front of the thigh, overlapping the territories of the ilioinguinal and iliohypogastric nerves.

Course and supply

Arises from

Ventral rami of L1 and L2, uniting within psoas major; emerges through the anterior surface of the muscle.

Ends in

Divides on psoas into a genital branch, which runs through the inguinal canal, and a femoral branch, which passes under the inguinal ligament to the thigh skin.

Supplies

Motor to the cremaster through the genital branch; sensory to a small area of groin skin and to the skin over the upper femoral triangle.