Genitofemoral Block

Origin

The genitofemoral nerve is mainly a sensory nerve, and it is formed from the first and second lumbar nerves (Figure 1) in the substance of the psoas major muscle. The nerve emerges on the ventral surface of the muscle along its medial border at the level of the third and fourth lumbar vertebra. The nerve descends on the surface of the psoas major muscle behind the ureter, and divides into the genital and femoral branches at a variable distance above the inguinal ligament. The genital branch enters the inguinal canal through the deep inguinal ring and passes through the inguinal canal (man) or round ligament of the uterus (woman). The femoral branch accompanies the external iliac artery and below the inguinal ligament remains enveloped by the femoral vascular sheath lateral to the femoral artery.

Legend: Pubic Tubercle Inguinal Ligament Anterior Superior Iliac Spine Obturator Nerve Accessory Obturator Nerve Superior Ramus of the Pubic Bone Genitofemoral Nerve Femoral Nerve Sciatic Nerve

Innervation

The genital branch of the genitofemoral nerve supplies motor fibers to the cremasteric muscle and sensory fibers to the skin over the scrotum in men and to the mons pubis and labia majora in women. The femoral branch innervates the skin over the femoral triangle.

Anatomical facts of clinical importance

The genitofemoral nerve may be affected by an abscess within the psoas major muscle, or by a pelvic mass. The femoral branch may be damaged by injuries to the groin. The genital branch on the other hand can be affected during inguinal hernia repair. Both branches can be affected by postoperative scaring on the anterior aspect of the psoas muscle.

• In conjunction with ilioinguinal and iliohypogastric nerve blocks for inguinal herniorrhaphy, orchiopexy or hydrocelectomy.
• In addition to femoral nerve block for long saphenous vein stripping [3].
• In diagnosis of genitofemoral neuralgia.

The block of the peripheral branches of the genitofemoral nerve is performed with the patient in supine position. The main anatomical landmarks are identified: the pubic tubercle, inguinal ligament, inguinal crease and femoral artery.

The femoral branch of the genitofemoral nerve is blocked by inserting the 25G/5-cm needle at the lateral border of the femoral artery at the inguinal crease. A fanlike infiltration of the subcutaneous tissue is made in a medial, caudal and cephalad direction with 10-15 ml of local anesthetic solution.

The genital branch of the genitofemoral nerve is blocked by infiltration of 10 ml of local anesthetic just lateral to the pubic tubercle, below the inguinal ligament.

A transpsoas technique

Recently a transpsoas technique to block genitofemoral nerve was described [6]. With the patient in prone position a 15-cm 21-gauge spinal needle is introduced paravertebraly, approximately 5 cm from the midline at the level of the L3-4 interspace. The needle is advanced toward the transverse processes of either L3 or L4. After noting the depth of the processes, the needle is redirected to pass between the tranverse processes in perpendicular fashion. The loss of resistance is used to identify, first psoas muscle compartment, and after further advan-cement, the space located anteriorly to the psoas major muscle. At this point, 2-3mL of local anesthetic is injected to block the genitofemoral nerve.

TIPS:

• The block of the superficial branches of the genitofemoral nerve is essentially an infiltration technique.
• Higher volume of local anesthetic (10 ml or more) is needed for consistent results.

The genitofemoral and obturator nerves are most commonly blocked by the lumbar plexus blocks, paravertebral blocks and epidural or spinal blocks. In many clinical applications, it is advantageous to achieve selective blocks of these nerves, rather then the blocks of entire lumbar plexus. In outpatient population, it is advantageous to use specific nerve blocks and limit anesthesia to the surgical field in order to avoid delayed recovery [3,7] and/or hemodynamic effects frequently associated with spinal or epidural anesthesia.

Isolated genitofemoral nerve blocks are extremely helpful in making accurate diagnosis and predicting prognosis in various pain disorders, such as in genitofemoral neuralgia (causalgia) [8].

During endoscopic prostate and bladder procedures, because of the proximity of the obturator nerve to the bladder wall and urethra, the nerve is frequently directly stimulated by the electro-surgical unit during. This results in a mass contraction of the adductor muscles and may result in serious complications, such as bladder wall perforation, bleeding, incomplete resection, and/or dissemination of the tumor [9, 10]. While muscle relaxants can be used to correct this problem, presently most operations are performed under neuraxial anesthesia. However, blocking the obturator nerve block distal to the level of stimulation completely abolishes these violent muscle contractions.

The obturator nerve block may be successfully used in diagnosing the causes of pain in the hip region. In patients with cerebral palsy, the abnormal muscle spasm of the adductors may be associated with dislocation or subluxation of the hip [11]. This can also further aggravate reflex spasms, with deterioration in the ability to walk. Block of the obturator nerve relieves both the spasm of the adductors and the hip pain. After the diagnosis is made, a series of phenol injections can be then used to maintain a satisfactory pain relief [11].

1. Sunderland S: Obturator nerve, in Sunderland S, (ed): Nerves and Nerve Injuries. Edinburgh: E.& S. Livingstone Ltd., 1968:1096-109.
2. Katz J, Renck H: Genitofemoral nerve, in Katz J, Renck H, (ed): Handbook of Thoraco-abdominal Nerve Blocks.Orlando: Grune & Stratton, INC, 1987:44.
3. Vloka JD, Hadzic A, Mulcare R, Lesser JB, Kitain E, Thys DM: Femoral nerve block versus spinal anesthesia for outpatients undergoing long saphenous vein stripping surgery. Anesth Analg 84:749-52, 1997.
4. Carron H, Korbon GA, Rowlingson JC: Abdominal Blocks, in Korbon GA, Rowlingson JC, (ed): Regional Anesthesia. Techniques and Clinical Applications. Orlando: Grune & Stratton, Inc., 1984:82-95.
5. Broadman L: Ilioinguinal, Iliohypogastric, and Genitofemoral Nerves, in Gay SG, (ed): Regional Anesthesia. An Atlas of Anatomy and Techniques.St. Louis: Mosby, 1996:247-54.
6. Hartrick CT: Genitofemoral nerve block: A transpsoas technique. Reg Anesth 19(6):432-3, 1994.
7. Vloka JD, Hadzic A, Mulcare R, Lesser JB, Koorn R, Thys DM: Combined blocks of the sciatic nerve at the popliteal fossa and posterior cutaneous nerve of the thigh for short saphenous vein stripping in outpatients: An alternative to spinal anesthesia. J Clin Anesth 9:618-22, 1997.
8. Laha RK, Rao S, Pidgeon CN, Dujovny M: Genitofemoral neuralgia. Surg Neurol 8:280, 1977.
9. Atanassoff PG, Weiss BM, Brull SJ: Lidocaine plasma levels following two techniques of obturator nerve block. J Clin Mon 8:535-9, 1996.
10. Augspurger R, Donohue RE: Prevention of obturator nerve stimulation during transurethral surgery. J. Urol. 123:170-1, 1980.
11. Trainer N, Bowser BL, Dahm L: Obturator nerve block for painful hip in adult cerebral palsy.