Ultrasound-guided genitofemoral nerve block is utilized as a diagnostic and therapeutic maneuver in the evaluation and treatment of groin and inner thigh pain thought to be mediated via the genitofemoral nerve. The most common pain syndrome mediated via the genitofemoral nerve is postoperative neuropathy secondary to surgical injuries to the genitofemoral nerve during cesarean sections, appendectomies, and inguinal hernia repairs. Less commonly, genitofemoral neuralgia can be seen in patients in their third trimester of pregnancy when a rapidly expanding abdomen causes a traction neuropathy of the nerve. The symptoms associated with ilioinguinal neuralgia depend on whether the main trunk of the nerve is damaged or if the injury is isolated to the femoral or genital branch of the nerve (Fig. 102.1). If the injury is isolated to the femoral branch of the genitofemoral nerve, the patient will complain of burning pain, paresthesias, and numbness in the skin over a small area of skin on the inside of the thigh. If the genital branch is damaged, the patient will complain of burning pain, paresthesias, and numbness in the skin overlying the labia majora in women and the bottom of the scrotum in men. The femoral branch of the genitofemoral nerve also innervates the round ligament in women and the cremasteric muscles in men.

Ultrasound-guided genitofemoral nerve block can also be utilized to provide surgical anesthesia for groin surgery, including inguinal herniorrhaphy when combined with ultrasound-guided ilioinguinal and iliohypogastric nerve block. Ultrasound-guided genitofemoral nerve block with local anesthetics can be employed as a diagnostic maneuver when performing differential neural blockade on an anatomic basis to determine if the patient’s groin pain and inner thigh pain are subserved by the genitofemoral nerve. If destruction of the genitofemoral nerve is being contemplated, ultrasound-guided genitofemoral nerve block with local anesthetic can provide prognostic information as to the extent of motor and sensory deficit the patient will experience following nerve destruction.

Ultrasound-guided genitofemoral nerve block with local anesthetic may also be used to provide postoperative pain relief following lower abdominal and groin surgeries and is useful in the treatment of persistent postoperative neuropathic pain following inguinal hernia surgery. Electromyography can distinguish genitofemoral nerve entrapment from lumbar plexopathy, lumbar radiculopathy, and diabetic polyneuropathy. Plain radiographs of the hip and pelvis are indicated in all patients who present with genitofemoral neuralgia to rule out occult bony pathology. Based on the patient’s clinical presentation, additional testing may be warranted, including a complete blood count, uric acid level, erythrocyte sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging of the lumbar plexus and retroperitoneum is indicated if tumor or hematoma is suspected. Ultrasound and computerized tomographic scanning is also indicated if pelvic mass or tumor or if abnormality of the testes or ovary is suspected (Fig. 102.2). The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

The genitofemoral nerve is derived from the L1 nerve root with a contribution from T12 in some patients (Fig. 102.3). The nerve exits the lateral border of the psoas muscle where it divides into a femoral and genital branch. 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. 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 (see Fig. 102.1).

Ultrasound-guided block of the genital branch of the genitofemoral nerve can be carried out by placing the patient in the supine position with the arms resting comfortably by the patient’s side (Fig. 102.4). A total of 8 mL of local anesthetic is drawn up in a 12-mL sterile syringe. If the painful condition
being treated is thought to have an inflammatory component, 40 to 80 mg of depot steroid is added to the local anesthetic. The femoral artery is then identified by palpation (Fig. 102.5). A linear high-frequency ultrasound transducer is placed in long axis over the previously identified femoral artery, and an ultrasound survey scan is obtained (Figs. 102.6 and 102.7). The ultrasound transducer is then slowly moved in a cephalad trajectory following the femoral artery until it begins to descend beneath the inguinal ligament into the abdominal cavity as it becomes the external iliac artery (Figs. 102.8 and 102.9). Color Doppler may be utilized to aid in the identification of this point of transition between the femoral and external iliac arteries (Fig. 102.10). When this point of transition is identified, the inguinal canal should be visible just above the external iliac artery, appearing as an ovoid structure containing tubular structures including the spermatic cord in males and the round ligament in women (Figs. 102.11 and 102.12). When the inguinal canal and its contents are identified on ultrasound imaging, the skin is prepped with anesthetic solution, and a 3½-inch, 22-gauge needle is advanced from the lateral border of the ultrasound transducer and advanced utilizing an outof-plane approach with the trajectory being adjusted under real-time ultrasound guidance until the needle tip is resting within the inguinal canal (Fig. 102.13). In women, after careful aspiration, the contents of the syringe are injected around the round ligament. In men, after careful aspiration, 4 mL of solution is injected within the spermatic cord while avoiding the testicular artery. Then after withdrawing the needle from the spermatic cord, after careful aspiration, 4 mL of solution is outside the spermatic cord, but within the inguinal canal. Color Doppler can aid in identification of the vessels within the spermatic cord (Fig. 102.14). The needle is then removed, and a sterile pressure dressing and ice pack are placed at the injection site.