Genitofemoral neuralgia is a painful condition that classically affects individuals who have undergone lower abdominal surgeries such as herniorrhaphy. The painful symptoms associated with genitofemoral neuralgia manifest along the distribution of the nerve. Overlaps of the cutaneous distribution of the GFN and other inguinal nerves, particularly the ilioinguinal nerve, make an accurate diagnosis difficult to achieve. It is essential for physicians to be able to identify differential diagnoses, to implement an effective pain management plan. Selective nerve blocks aid in the diagnosis and serve a therapeutic role. If selective nerve blocks are successful, nerve ablation techniques like can provide long-term pain relief.
Genitofemoral neuralgia was first described in 1942 by Magee, who coined the term genitofemoral “causalgia.” The majority of patients described by Magee presented with pain along the distribution of the GFN after undergoing appendicular surgery. Injury to the genitofemoral nerve is almost always secondary to direct trauma. Direct trauma is almost always the result of surgery. Complications following inguinal herniorrhaphy and laparoscopic varicocelectomy are cited relatively frequently and can stem from inflammation, neuroma formation, deafferentation, or entrapment. Entrapment neuropathy can occur from impingement from staples or tacks which are used to affix the prosthetic mesh, the mesh itself, direct injury, or myofascial scarring.
Additionally, it is not uncommon for genitofemoral neuralgia to be induced during the performance of a lumbar sympathetic block. Lumbar sympathetic blocks, which are traditionally performed by injecting a needle from a posterior position toward the anterolateral aspect of the vertebral body, may allow for the injected solution to leak back along the needle shaft and spread toward the genitofemoral nerve, acting as a noxious irritant on the nerve.
Other factors, such as an abscess or mass dwelling within or near the psoas major muscle, complications secondary to appendectomy, inguinal lymph node dissection, orchiectomy, total abdominal hysterectomy, abdominoplasty, iliac crest bone graft, femoral catheter placement, cesarean section, thermal damage following radiofrequency ablation of renal cell carcinoma, direct injury from an inguinal herniated mass and complications from leprosy have also been noted.
Aside from iatrogenic causes, review of the literature has revealed some instances of idiopathic genitofemoral neuropathy. O’Brien (1979) reported a patient with what appeared to be idiopathic genitofemoral neuralgia. Occupational history of the patient revealed they modeled extremely tight jeans. Bicycle riding has also been reported as another possible association with spontaneous genitofemoral neuralgia.
By far, the highest incidences of genitofemoral neuralgia are reported with laparoscopic and open herniorrhaphy procedures, including whether mesh or tension-free repairs are done. There are multiple mechanisms for the pathogenesis of genitofemoral neuralgia post-herniorrhaphy. Nerve entrapments within scar tissue or fibrous adhesions are likely to cause the onset of nociceptive pain and paresthesias along the distribution of the GFN. Accidental ligation of the nerve may also lead to neuropathic neuralgia. The cremasteric artery is purposely ligated during herniorrhaphy, and the genital branch of the GFN’s proximity to this artery leaves it susceptible to ligation as well. Neuromas may also develop as a result of the ligation of the genital branch, thus causing the symptoms of genitofemoral neuralgia. Indirect nerve irritation may develop in the presence of an inflammatory process such a granulomatous formation compressing the nerve and causing nociceptive pain. In addition, meshomas and mesh-related neuritis may occur from direct contact with the GFN and its branches, thus the surgeon must use caution in placement and fixation of meshes.
Genitofemoral neuralgia is defined as chronic pain distributed along the cutaneous region in the groin and inner thigh innervated by the genitofemoral nerve. The symptoms of this neuropathy include paresthesias, burning pain, and hypoalgesia in the groin region and spreading from the lower abdomen to the medial aspect of the thigh. It may present with scrotal pain in male, while females experience symptoms radiating to the labia majora and mons pubis. The pain and paresthesias are exacerbated by walking and hip extension. Symptoms can be so severe that patients assume a bent over position when standing up in attempt to ameliorate their discomfort. In some patients, assuming a recumbent position and flexing the hip is noted to relieve pain.
Obtaining an accurate diagnosis of genitofemoral neuralgia is difficult, due to the fact that it presents in a very similar way to other inguinal neuralgias. There is significant sensory overlap between the ilioinguinal and GFNs, so it is important to consider ilioinguinal neuralgia as a differential diagnosis to effectively manage this neuropathy. If clinicians misdiagnose genitofemoral neuralgia as ilioinguinal neuropathy, there is a risk of mistreatment and unnecessary surgical exploration of the inguinal region. Another obstacle to swift diagnosis and treatment of genitofemoral neuralgia is that temporary pain and paresthesia immediately following herniorrhaphy is common. A period of time might be necessary in order for physicians to distinguish transient postoperative pain with a chronic situation that implies severe nerve damage or entrapment.
The use of selective nerve blocks as a diagnostic technique is widely supported in the literature. If administration of an ilioinguinal nerve block causes relief of the patient’s painful symptoms, a diagnosis of ilioinguinal neuralgia can be established and the proper management implemented. However, if such a nerve block does not provide relief, a block of the L1 and L2 nerve plexus may identify the GFN as the cause of chronic pain. While this method significantly helps in determining which nerve is the root cause of pain, it is not effective in all patients.
Conservative medical and non-invasive management should always be tried first. This includes non-pharmacological treatments like TENS and acupuncture and anti neuropathic medications like Amitriptyline, Gabapentin, and Pregabalin. Topical treatment with lidocaine plasters or Capsaicin cream can be helpful in some patients.
Ultrasound-guided nerve block injections have also proven valuable in the management of genitofemoral neuralgia. The use of ultrasound guidance aids the clinician in making a more precise injection, so it shows itself to be safe and most efficacious in the treatment of neuropathic pain. However, it should also be noted that nerve blocks do not present a permanent solution to chronic neuropathic pain, thus the repetition of treatment may be required.
The use of ultrasound-guided ablative techniques has also shown utility when pharmacological treatments are unable to treat continued chronic pain. One particular ablative therapy is pulsed radiofrequency (PRF) ablation. PRF ablation has been shown to provide long-term pain relief by causing neurolysis with minimal to no risk of neuroma formation.
Similar to RF ablation, cryoablation involves the lysis of a nerve’s myelin sheath and axon with preservation of the epineurium and perineurium to facilitate nerve regeneration. Proponents of cryoanalgesic ablation suggest distinct advantages of this procedure over GFN neurectomy. These include higher rates of complete analgesia, and, due to the superficial anterior approach of cryoanalgesia there is less likelihood of compromising the hernia repair itself (F. Cryoablation is also reported to provide immediate pain relief along the distribution of the nerve, while other procedures may show a delay in onset of analgesic effects. Using cryoablation to treat neuropathic pain is safe, with minimal risk of neuroma formation. In addition, this procedure under ultrasound guidance shows increased nerve block efficacy with minimal radiation exposure as compared with CT or fluoroscopy-guided techniques. Treating genitofemoral neuralgia with cryoablation under ultrasound guidance seems to be a promising method to relieve the debilitating symptoms associated with this neuropathy.