ilioinguinal

The ilioinguinal nerve is a sensory and motor branch of the lumbar plexus, arising mainly from the first lumbar spinal nerve (L1) with occasional contribution from the T12 nerve. It travels from the lumbar region into the abdominal wall and groin, transmitting both somatic motor and sensory fibers. Its primary clinical relevance lies in its cutaneous distribution and its course through the inguinal region.

After arising from the lumbar plexus, the ilioinguinal nerve emerges near the lateral border of the psoas major and descends across the iliac crest. It lies between the internal oblique and transversus abdominis muscles and enters the inguinal canal. In males it accompanies the spermatic cord through the canal; in females it accompanies the round ligament. The nerve typically emerges at the superficial inguinal ring, where it provides cutaneous innervation.

Sensory distribution includes the skin of the upper medial thigh, the root of the penis and the anterior scrotum in males, and the mons pubis and labia majora in females. Some fibers may extend to adjacent groin and proximal thigh regions. Motorly, the ilioinguinal nerve supplies small muscular branches to the internal oblique and transversus abdominis muscles, contributing to abdominal wall function rather than a primary motor role.

Clinical significance centers on nerve injury or entrapment during inguinal hernia repair or abdominal surgery, which can cause numbness or neuropathic pain in its sensory territory. Ilioinguinal nerve block or regional anesthesia may be used for groin procedures.