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Genitofemoral Neuralgia
81 Genitofemoral Neuralgia ICD-10 CODE G57.90
THE CLINICAL SYNDROME 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 traumatic injury to the nerve, including direct blunt trauma and damage during inguinal herniorrhaphy and pelvic surgery. Rarely, genitofemoral neuralgia occurs spontaneously. The genitofemoral nerve arises from fibers of the L1 and L2 nerve roots and passes through the substance of the psoas muscle, where it divides into a genital and a femoral 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 inner 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 passes with the spermatic cord to innervate the cremasteric muscles and provide sensory innervation to the bottom of the scrotum.
SIGNS AND SYMPTOMS Genitofemoral neuralgia manifests as paresthesias, burning pain, and occasionally numbness over the lower abdomen that radiates to 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 (Fig. 81.1); the pain does not radiate below the knee. The pain of genitofemoral neuralgia
Inguinal lig. Genitofemoral n. Psoas major m.
FIG 81.1 The pain of genitofemoral neuralgia radiates into the inner thigh of men and women and into the labia majora in women and the inferior scrotum in men.
314
CHAPTER 81 Genitofemoral Neuralgia worsens with extension of the lumbar spine, which puts traction on the nerve. Therefore patients with genitofemoral neuralgia often assume a bent-forward, novice skier’s position (see Fig. 81.1). 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 be present. Tinel sign may be elicited by tapping over the genitofemoral nerve at the point where it passes beneath the inguinal ligament.
315
Genitofemoral n.
Inguinal lig.
TESTING Electromyography (EMG) 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 disease. 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 (MRI) of the lumbar plexus is indicated if tumor or hematoma is suspected. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.
DIFFERENTIAL DIAGNOSIS
Femoral branch of genitofemoral n.
Genital branch of genitofemoral n.
Pubic tubercle
FIG 81.2 Correct needle placement for genitofemoral nerve block. (From Waldman SD. Atlas of interventional pain management. Philadelphia: Saunders; 1998:374.)
Lesions of the lumbar plexus caused by trauma, hematoma, tumor, diabetic neuropathy, or inflammation can mimic the pain, numbness, and weakness of genitofemoral neuralgia and must be excluded. Further, significant variability exists in the anatomy of the genitofemoral nerve, which can result in significant variation in the clinical presentation.
TREATMENT Initial treatment of genitofemoral neuralgia consists of simple analgesics, nonsteroidal antiinflammatory drugs, or cyclooxygenase-2 inhibitors. Avoidance of repetitive activities thought to exacerbate the pain (e.g., squatting or sitting for prolonged periods) may also ameliorate the patient’s symptoms. Pharmacologic treatment is usually disappointing, however, in which case genitofemoral nerve block with local anesthetic and steroid is required. Genitofemoral nerve block is performed with the patient in the supine position; a pillow can be placed under the patient’s knees if lying with the legs extended increases the pain because of traction on the nerve. The genital branch of the genitofemoral nerve is blocked as follows: The pubic tubercle is identified by palpation, and a point just lateral to it is identified and prepared with antiseptic solution. A 1 1 2-inch, 25-gauge needle is advanced at an oblique angle toward the pubic symphysis (Fig. 81.2). A total of 3 to 5 mL of 1% preservativefree lidocaine in solution with 80 mg methylprednisolone is injected in a fanlike manner as the needle pierces the inguinal ligament. Care must be taken not to insert the needle deeply
FIG 81.3 Relationship of the genitofemoral nerve to the femoral artery. Color Doppler image of the femoral artery as it begins to descend beneath the inguinal ligament into the abdominal cavity as it becomes the external iliac artery.
enough to enter the peritoneal cavity and perforate the abdominal viscera. Ultrasound needle guidance will help increase the accuracy of needle placement as well as decrease the incidence of needle-related complications (Fig. 81.3). The femoral branch of the genitofemoral nerve is blocked by identifying the middle third of the inguinal ligament. After preparation of the skin with antiseptic solution, 3 to 5 mL of 1% lidocaine is infiltrated subcutaneously just below the ligament (see Fig. 81.2). Care must be taken not to enter the femoral artery or vein or to block the femoral nerve
316
SECTION X Abdominal and Groin Pain Syndromes
inadvertently. The needle must be kept in a subcutaneous position to avoid entering the peritoneal cavity and perforating the abdominal viscera. If the patient has an inflammatory component to the pain, the local anesthetic is combined with 80 mg methylprednisolone and injected in incremental doses. Subsequent daily nerve blocks are carried out in a similar manner, by substituting 40 mg methylprednisolone for the initial 80-mg dose. Because of overlapping innervation of the ilioinguinal and iliohypogastric nerves, it is usually not necessary to block branches of each nerve during genitofemoral nerve block. After injection of the solution, pressure is applied to the injection site to decrease the incidence of ecchymosis and hematoma formation, which can be quite dramatic, especially in anticoagulated patients. Ultrasound needle guidance will help increase the accuracy of needle placement as well as decrease the incidence of needle-related complication when blocking the femoral branch of the genitofemoral nerve. For patients who do not rapidly respond to genitofemoral nerve block, consideration should be given to epidural steroid injection of the L1-L2 segments.
COMPLICATIONS AND PITFALLS Because of the anatomy of the genitofemoral nerve, damage to or entrapment of the nerve anywhere along its course can produce a similar clinical syndrome. Therefore a careful search for pathologic processes at the L1-L2 spinal segments and along the path of the nerve in the pelvis is mandatory in all patients who present with genitofemoral neuralgia without a history of inguinal surgery or trauma to the region. The major complications of genitofemoral nerve block are ecchymosis and hematoma formation. If the needle is too deep and enters the peritoneal cavity, perforation of the colon may result in the formation of an intraabdominal abscess and
fistula. Early detection of infection is crucial to avoid potentially life-threatening sequelae.
CLINICAL PEARLS Genitofemoral neuralgia is a common cause of lower abdominal and pelvic pain; genitofemoral nerve block is a simple technique that can produce dramatic pain relief. If a patient presents with pain suggestive of genitofemoral neuralgia and does not respond to genitofemoral nerve block, lesions more proximal in the lumbar plexus or an L1 radiculopathy should be considered. Such patients often respond to epidural steroid blocks. EMG and MRI of the lumbar plexus are indicated in this patient population to rule out other causes of genitofemoral pain, including malignant disease invading the lumbar plexus or epidural or vertebral metastatic disease at T12-L1.
SUGGESTED READINGS Ahmadian A, Abel N, Dakwar E. Injuries to the nerves of the abdominopelvic region. In: Tubbs RS, Rizk E, Shoja MM, et al, eds. Nerves and nerve injuries. San Diego: Academic Press; 2015:545–555. Belanger GV, VerLee GT. Diagnosis and surgical management of male pelvic, inguinal, and testicular pain. Surg Clin North Am. 2016;96(3):593–613. Kretschmer T, Heinen C. Iatrogenic injuries of the nerves. In: Tubbs RS, Rizk E, Shoja MM, et al, eds. Nerves and nerve injuries. San Diego: Academic Press; 2015:557–585. Nguyen DK, Amid PK, Chen DC. Groin pain after inguinal hernia repair. Adv Surg. 2016;50(1):203–220. Waldman SD. Genitofemoral nerve block. In: Atlas of interventional pain management. 4th ed. Philadelphia: Elsevier; 2017:470–473. Waldman SD. Genitofemoral neuralgia. In: Pain review. 2nd ed. Philadelphia: 2017:285–286.
THE CLINICAL SYNDROME 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 traumatic injury to the nerve, including direct blunt trauma and damage during inguinal herniorrhaphy and pelvic surgery. Rarely, genitofemoral neuralgia occurs spontaneously. The genitofemoral nerve arises from fibers of the L1 and L2 nerve roots and passes through the substance of the psoas muscle, where it divides into a genital and a femoral 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 inner 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 passes with the spermatic cord to innervate the cremasteric muscles and provide sensory innervation to the bottom of the scrotum.
SIGNS AND SYMPTOMS Genitofemoral neuralgia manifests as paresthesias, burning pain, and occasionally numbness over the lower abdomen that radiates to 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 (Fig. 81.1); the pain does not radiate below the knee. The pain of genitofemoral neuralgia
Inguinal lig. Genitofemoral n. Psoas major m.
FIG 81.1 The pain of genitofemoral neuralgia radiates into the inner thigh of men and women and into the labia majora in women and the inferior scrotum in men.
314
CHAPTER 81 Genitofemoral Neuralgia worsens with extension of the lumbar spine, which puts traction on the nerve. Therefore patients with genitofemoral neuralgia often assume a bent-forward, novice skier’s position (see Fig. 81.1). 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 be present. Tinel sign may be elicited by tapping over the genitofemoral nerve at the point where it passes beneath the inguinal ligament.
315
Genitofemoral n.
Inguinal lig.
TESTING Electromyography (EMG) 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 disease. 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 (MRI) of the lumbar plexus is indicated if tumor or hematoma is suspected. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.
DIFFERENTIAL DIAGNOSIS
Femoral branch of genitofemoral n.
Genital branch of genitofemoral n.
Pubic tubercle
FIG 81.2 Correct needle placement for genitofemoral nerve block. (From Waldman SD. Atlas of interventional pain management. Philadelphia: Saunders; 1998:374.)
Lesions of the lumbar plexus caused by trauma, hematoma, tumor, diabetic neuropathy, or inflammation can mimic the pain, numbness, and weakness of genitofemoral neuralgia and must be excluded. Further, significant variability exists in the anatomy of the genitofemoral nerve, which can result in significant variation in the clinical presentation.
TREATMENT Initial treatment of genitofemoral neuralgia consists of simple analgesics, nonsteroidal antiinflammatory drugs, or cyclooxygenase-2 inhibitors. Avoidance of repetitive activities thought to exacerbate the pain (e.g., squatting or sitting for prolonged periods) may also ameliorate the patient’s symptoms. Pharmacologic treatment is usually disappointing, however, in which case genitofemoral nerve block with local anesthetic and steroid is required. Genitofemoral nerve block is performed with the patient in the supine position; a pillow can be placed under the patient’s knees if lying with the legs extended increases the pain because of traction on the nerve. The genital branch of the genitofemoral nerve is blocked as follows: The pubic tubercle is identified by palpation, and a point just lateral to it is identified and prepared with antiseptic solution. A 1 1 2-inch, 25-gauge needle is advanced at an oblique angle toward the pubic symphysis (Fig. 81.2). A total of 3 to 5 mL of 1% preservativefree lidocaine in solution with 80 mg methylprednisolone is injected in a fanlike manner as the needle pierces the inguinal ligament. Care must be taken not to insert the needle deeply
FIG 81.3 Relationship of the genitofemoral nerve to the femoral artery. Color Doppler image of the femoral artery as it begins to descend beneath the inguinal ligament into the abdominal cavity as it becomes the external iliac artery.
enough to enter the peritoneal cavity and perforate the abdominal viscera. Ultrasound needle guidance will help increase the accuracy of needle placement as well as decrease the incidence of needle-related complications (Fig. 81.3). The femoral branch of the genitofemoral nerve is blocked by identifying the middle third of the inguinal ligament. After preparation of the skin with antiseptic solution, 3 to 5 mL of 1% lidocaine is infiltrated subcutaneously just below the ligament (see Fig. 81.2). Care must be taken not to enter the femoral artery or vein or to block the femoral nerve
316
SECTION X Abdominal and Groin Pain Syndromes
inadvertently. The needle must be kept in a subcutaneous position to avoid entering the peritoneal cavity and perforating the abdominal viscera. If the patient has an inflammatory component to the pain, the local anesthetic is combined with 80 mg methylprednisolone and injected in incremental doses. Subsequent daily nerve blocks are carried out in a similar manner, by substituting 40 mg methylprednisolone for the initial 80-mg dose. Because of overlapping innervation of the ilioinguinal and iliohypogastric nerves, it is usually not necessary to block branches of each nerve during genitofemoral nerve block. After injection of the solution, pressure is applied to the injection site to decrease the incidence of ecchymosis and hematoma formation, which can be quite dramatic, especially in anticoagulated patients. Ultrasound needle guidance will help increase the accuracy of needle placement as well as decrease the incidence of needle-related complication when blocking the femoral branch of the genitofemoral nerve. For patients who do not rapidly respond to genitofemoral nerve block, consideration should be given to epidural steroid injection of the L1-L2 segments.
COMPLICATIONS AND PITFALLS Because of the anatomy of the genitofemoral nerve, damage to or entrapment of the nerve anywhere along its course can produce a similar clinical syndrome. Therefore a careful search for pathologic processes at the L1-L2 spinal segments and along the path of the nerve in the pelvis is mandatory in all patients who present with genitofemoral neuralgia without a history of inguinal surgery or trauma to the region. The major complications of genitofemoral nerve block are ecchymosis and hematoma formation. If the needle is too deep and enters the peritoneal cavity, perforation of the colon may result in the formation of an intraabdominal abscess and
fistula. Early detection of infection is crucial to avoid potentially life-threatening sequelae.
CLINICAL PEARLS Genitofemoral neuralgia is a common cause of lower abdominal and pelvic pain; genitofemoral nerve block is a simple technique that can produce dramatic pain relief. If a patient presents with pain suggestive of genitofemoral neuralgia and does not respond to genitofemoral nerve block, lesions more proximal in the lumbar plexus or an L1 radiculopathy should be considered. Such patients often respond to epidural steroid blocks. EMG and MRI of the lumbar plexus are indicated in this patient population to rule out other causes of genitofemoral pain, including malignant disease invading the lumbar plexus or epidural or vertebral metastatic disease at T12-L1.
SUGGESTED READINGS Ahmadian A, Abel N, Dakwar E. Injuries to the nerves of the abdominopelvic region. In: Tubbs RS, Rizk E, Shoja MM, et al, eds. Nerves and nerve injuries. San Diego: Academic Press; 2015:545–555. Belanger GV, VerLee GT. Diagnosis and surgical management of male pelvic, inguinal, and testicular pain. Surg Clin North Am. 2016;96(3):593–613. Kretschmer T, Heinen C. Iatrogenic injuries of the nerves. In: Tubbs RS, Rizk E, Shoja MM, et al, eds. Nerves and nerve injuries. San Diego: Academic Press; 2015:557–585. Nguyen DK, Amid PK, Chen DC. Groin pain after inguinal hernia repair. Adv Surg. 2016;50(1):203–220. Waldman SD. Genitofemoral nerve block. In: Atlas of interventional pain management. 4th ed. Philadelphia: Elsevier; 2017:470–473. Waldman SD. Genitofemoral neuralgia. In: Pain review. 2nd ed. Philadelphia: 2017:285–286.