Background and indication: The genitofemoral nerve is a mixed nerve formed from the roots of L1 and L2. During its course, the nerve divides into femoral and genital branches. The genital branch supplies sensory innervation to the pubic mons and the scrotum or labia majora. The femoral branch supplies the skin inferior to the medial aspect of the inguinal ligament. Combination of the genitofemoral nerve block with the ilioinguinal-iliohypogastric nerve blocks during inguinal herniorrhaphy has been described. This addition may be advantageous by means of blocking nociception during periods of sac traction. It may also be used independently for surgical incisions of the scrotal skin. Another application of the genitofemoral nerve block is genitofemoral nerve entrapment neuralgias occurring as a consequence of inguinal surgery.

Anatomy: The genitofemoral nerve receives contributions from the L1 and L2 ventral rami. At the level of the third and fourth lumbar vertebrae, the genitofemoral nerve passes through the psoas muscle and continues extraperitoneally, on the ventral surface of the muscle, deep to the psoas fascia. The nerve typically divides into femoral and genital branches at a location lateral to the common and external iliac arteries, although the point of division is variable. After this split, the genital branch passes along the psoas major and through the internal inguinal ring of the transversalis fascia. In males, it descends posterior to the spermatic cord to innervate the cremaster muscle and part of the scrotal skin. In females, the genital branch travels with the round ligament to supply sensory innervation to the pubic mons and labia majora. The relationship of the genital branch to the spermatic cord is extremely variable with the nerve running outside, inside, ventral, or dorsal to the spermatic cord. The nerve may also incorporate with the cremaster muscle. Alternatively, the femoral branch of the genitofemoral nerve courses superficially outside the inguinal canal, piercing the fascia lata to terminate in the skin overlying the anterior superior thigh and groin.

Patient position: Supine.

Probe: A broadband high-frequency linear array transducer.