Genitofemoral Nerve Block


Indications and Clinical Considerations

Genitofemoral neuralgia is one of the most common causes of lower abdominal and pelvic pain encountered in clinical practice. It may be caused by compression of or damage to the genitofemoral nerve anywhere along its path. The most common causes of genitofemoral neuralgia involve injury to the nerve induced by trauma, including direct blunt trauma to the nerve, as well as damage during inguinal herniorrhaphy and pelvic surgery. Rarely, genitofemoral neuralgia will occur spontaneously.

Genitofemoral neuralgia manifests as paresthesias, burning pain, and, occasionally, numbness over the lower abdomen that radiates into the inner thigh in both men and women and into the labia majora in women and the bottom of the scrotum and cremasteric muscles in men. The pain does not radiate below the knee. The pain of genitofemoral neuralgia is made worse by extension of the lumbar spine, which puts traction on the nerve. Patients with genitofemoral neuralgia will often assume a bent-forward novice skier’s position.

Physical findings include sensory deficit in the inner thigh, base of the scrotum, or labia majora in the distribution of the genitofemoral nerve. Weakness of the anterior abdominal wall musculature may occasionally be present. A Tinel sign may be elicited by tapping over the genitofemoral nerve at the point where it passes beneath the inguinal ligament. As mentioned previously, the patient may assume a bent-forward novice skier’s position.

Clinically Relevant Anatomy

The genitofemoral nerve arises from fibers of the L1 and L2 nerve roots. It passes through the substance of the psoas muscle, where it divides into a genital branch and a femoral branch ( Fig. 142.1 ). The femoral branch passes beneath the inguinal ligament along with the femoral artery and provides sensory innervation to a small area of skin on the inside of the thigh ( Fig. 142.2 ). The genital branch passes through the inguinal canal to provide innervation to the round ligament of the uterus and labia majora in women. In men, the genital branch of the genitofemoral nerve passes with the spermatic cord to innervate the cremasteric muscles and provide sensory innervation to the bottom of the scrotum.

FIG. 142.1, Main trunk of the genitofemoral nerve (GFN) coursing over the psoas muscle elevated by the tip of the clamp.

FIG. 142.2, The femoral branch passes beneath the inguinal ligament along with the femoral artery and provides sensory innervation to a small area of skin on the inside of the thigh. n., Nerve.

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