Nerve injury can occur from multiple pathologic states. Symptoms of neuropathy can be caused by compression, stretching, contusion, crushing, partial or complete transection, electrical damage, neuroma formation, entrapment, or other trauma to the nerve in question [6, 9]. The location of the GFN makes it especially vulnerable to compression, trauma from surgical instruments, and inadvertent transection during surgery. Understanding its anatomy makes it easy to understand why the most common etiology for genitofemoral neuralgia is iatrogenic following abdominal/pelvic surgery [9].

In general, there is a 2 % incidence of nerve injury after pelvic surgery [16]. A review of the literature identifies reports of GFN injury following cesarean deliveries, abdominal lymph node biopsies, hernia repair surgeries, open herniorrhaphy, appendectomies, varicocele excision, trocar insertion in laparoscopies, and other surgeries in the inguinal region [1, 9]. The nerve can be injured by compression from retractors, entrapment, stretching, or even transection during dissection or movement of structures in the area [1, 16]. With newer operative approaches, the incidence of genitofemoral neuralgia has decreased. For example, fibrous tissue from open appendectomy scars was known to cause neuralgia of the femoral branch of the GFN via entrapment and compression. Incidence has decreased with the laparoscopic approach.

Other etiologies for injury to the GFN are trauma and idiopathic genitofemoral neuralgia. Pregnancy, retroperitoneal trauma, and trauma to the inguinal ligament are all instances of intrapelvic trauma that can give rise to genitofemoral neuralgia. Fortunately, the incidence of trauma to the GFN is rare; however, when it does occur, it can result in debilitating chronic pain. A case report from 1979 proposed tight-fitting jeans to be the etiology of genitofemoral neuralgia in one patient, and in 2001, a case report proposed bicycle riding as a potential cause of idiopathic genitofemoral neuralgia [9].

The first step in diagnosis begins with a thorough history and physical exam, as well as good knowledge of the innervation and anatomy of the groin region. The history should include age, gender, medical comorbidities, social history, recent surgical history, and type and approach of surgery (open vs. laparoscopic), history of chronic pain syndromes, history of preoperative pain, and any postoperative complications. A complete pain assessment is also a critical part of the history. A focused physical exam is necessary to confirm or rule out other potential etiologies of pain. On exam, it is important to check sensory dermatomes, motor function, reflexes, and gait. Lumbar spine range of motion should be assessed with flexion, extension, and lateral rotation of the spine. To rule out any lumbar spine disease, physical maneuvers can be very useful. For example, facet disease can be assessed by having the patient remain in a seated position while they twist their torso, and then extend the spine, putting a load on the facet joints. Pain with this maneuver may indicate facet disease. A positive straight leg raise (patient in supine position and examiner passively raising the patient’s leg without bending the knee) can indicate neural compression originating at the spine. A positive Patrick’s test (also known as FABER for flexion, abduction, and external rotation of the hip) may indicate hip joint pain. Sacroiliac (SI) joint disease can be tested using the Gaenslen test, which is done in the supine position, with one hip completely flexed (knee brought to the chest) and the other hip extended (leg allowed to fall over the side of the table). Both SI joints are flexed with this maneuver and pain can indicate SI joint disease, hip pathology, and L4 nerve root lesion or even stress on the femoral nerve. If other possible causes of pain are ruled out, neuropathic pain can be considered. Pain on palpation over the inguinal region or pubic tubercle can add some confirmation to the diagnosis of genitofemoral neuralgia, and tapping over an area of local tenderness (Tinel’s sign) can reproduce neuropathic pain symptoms [6, 17].

Initial investigation into chronic groin pain should always try to identify and rule out non-neuropathic causes, such as a recurrent hernia or mesh infection. Using the history, physical, a clinical evaluation, and imaging studies such as ultrasound or magnetic resonance imaging (MRI), any potential non-neuropathic pain etiologies should be eliminated. Such causes need to be explored immediately because proper treatment is often required urgently to prevent further complications such as an increased risk of chronic pain development [6].

Pain from genitofemoral neuralgia often presents as groin pain below the inguinal ligament, radiating to the genital area and superior medial and anterior thigh. Pain in the inguinal region after a hernia repair that is most concentrated in the testicular region (orchialgia) is indicative of neuralgia of the genital branch of the GFN. Orchialgia can be idiopathic or non-idiopathic (infection, tumors, varicocele, spermatocele, or complication of surgery such as vasectomy or inguinal hernia repair). One case study from 2014 described a case of idiopathic chronic orchialgia that was confirmed by local nerve block to be attributed to the genital branch of the GFN [34]. Due to anatomic variability, it becomes difficult to pinpoint the source of the pain by symptoms alone and further diagnostic studies are often necessary.

Accurate diagnosis of genitofemoral neuralgia is difficult because of overlapping and varying areas of innervation of different nerves in the inguinal region [1]. The differential diagnosis for any chronic groin pain following a surgery in the abdominal or pelvic region should include genitofemoral neuralgia along with ilioinguinal neuralgia. One study on human cadavers found four different branching patterns of the genitofemoral and ilioinguinal nerves leading to four different patterns of cutaneous innervation. The cadavers were only 40.6 % of the time symmetric bilaterally; a patient can have different cutaneous innervation patterns on different sides of their groin [29]. Distinguishing among the different neuralgias can be done by different selective diagnostic blocks to determine the true etiology of the pain. Accurate diagnosis is necessary to prevent incorrect treatment (and potentially unnecessary surgical exploration) since different pelvic neuropathies have different treatment modalities [1, 9]. (See Fig. 2.2).

A diagnostic selective nerve block technique was identified in 2006 in an attempt to eliminate incorrect diagnoses when ilioinguinal and genitofemoral neuralgias were both being considered [9]. The ilioinguinal nerve block is a technically simpler procedure and therefore it is done first to rule out ilioinguinal neuropathy (approximately 2–3 cm inferior and medial to the anterior superior iliac spine (ASIS)) [28]. If the nerve block does not relieve the patient’s symptoms, ilioinguinal neuralgia can be ruled out. The next diagnostic tool should be a paravertebral L1/L2 nerve plexus block to determine whether the GFN is the culprit [9, 19]. This approach has been well documented; however, it may not always be successful. Other approaches (e.g., anteriorly at the level of the inguinal ligament, or superior lateral to the pubic tubercle) to diagnostically or therapeutically block the GFN have proved difficult since the GFN is retroperitoneal and not without risk. With a blind technique, structures such as the spermatic cord, vas deferens, testicular artery, and the peritoneum can be harmed [28]. In 2010, a computerized tomography (CT)-guided trans-psoas approach was described by Parris et al. The basis of the technique was to target a location of the nerve proximal to the injury, so impulses were blocked en route distally from the injured site, traveling proximally to the central nervous system. Their technique proved to be an effective option in a diagnostic evaluation of the GFN, and a potentially therapeutic option (via radiofrequency and phenol ablation, although long-term relief was not achieved) [9, 27]. An ultrasound-guided approach to block the genital branch of the GFN was described by Peng et al. in 2008, by identifying the spermatic cord on ultrasound one finger breadth lateral to the pubic tubercle, and injecting local anesthetic (without epinephrine to avoid the possibility of vasoconstriction of the testicular artery) both inside and outside of the spermatic cord [28]. In 2014, Terkawi et al. described identifying the spermatic cord on ultrasound by identifying the inferior epigastric vessels under the rectus sheath and moving caudally to localize where the inferior epigastric artery joins the external iliac artery. The spermatic cord can be found medial to their intersection point. Another approach described was to locate the femoral artery, follow it superiorly until it joins with the external iliac artery and at that level, medially shift to find the spermatic cord. In the case study, the diagnostic block proved confirmatory as the patient reported pain relief lasting 6 weeks [34] (see Fig. 2.3).

Many algorithms have been suggested for the treatment of chronic groin pain, although none have been proven with randomized trials. There is currently no consensus for any one specific algorithm or even criteria for nonpharmacologic, pharmacologic, or surgical treatment. In general, the management for genitofemoral neuralgia, such as all chronic pain syndromes, starts with noninvasive methods. Avoiding exacerbating factors is a key factor in management; however, maintaining a sedentary lifestyle if even walking causes pain is no longer recommended. Physical and psychological therapies include massage, physiotherapy, myofascial release, and acupuncture. Acupuncture is one of the oldest methods of achieving analgesia, dating back over 3000 years and originating in China. According to the World Health Organization, the use of acupuncture in postoperative pain has been confirmed in controlled studies and is well recognized. The effect of acupuncture to relieve acute postoperative pain after inguinal surgery has been studied and shown to be effective [33]. Early research demonstrates a place for acupuncture in chronic pain treatment as well, for example, to treat chronic low back pain, knee osteoarthritis, and prostatitis/chronic pelvic pain. One study focused on investigating at brain regions via neuroimaging that were known to have dysregulation in chronic pain. The study indicated that repeat acupuncture might work by restoring balance in important brain regions associated with chronic pain, specifically the periaqueductal gray, medial frontal cortex, and bilateral hippocampus. Balancing the connectivity in the important brain regions via acupuncture can potentially alter pain-related memory and attention [13]. Although massage therapy has not been specifically studied with regard to genitofemoral neuralgia, there have been studies evaluating the effectiveness of massage therapy on neuropathy-related pain such as pain from carpal tunnel syndrome and fibromyalgia. Preliminary-positive support for the treatment includes findings such as decreased pain as well as decreased depression and anxiety in the experimental group patients, including studies on chronic pain syndromes [35]. Other therapies such as myofascial release, heat, physical therapy, and topical analgesics have been attempted for chronic pain, with short-term varying success rates, and limited long-term pain relief [6].

Pharmacological treatment involves multiple medication options, which are recommended in a stepwise approach. Topical anesthetics such as lidocaine patches can be tried initially. Next in line for medical management includes tricyclic antidepressants (TCAs), which have been proven to be effective in treating neuropathic pain. If there is no improvement of symptoms, medications such as gabapentin (inhibiting glutamate release in the spinal cord dorsal horn) and pregabalin can be used, followed by opioids [1, 19]. Adjunctive medications such as non-steroidal anti-inflammatory drugs (NSAIDs), other anti-epileptics, selective serotonin reuptake inhibitors (SSRIs), selective serotonin/norepinephrine reuptake inhibitors (SNRIs), tramadol, and capsaicin cream can also be used as supplementation [1]. In many studies, NSAIDs were used as the first-line pharmacological therapy and gabapentin or oral steroids as second line [19]. However, the efficacy of any certain regimen has not been proven, and although recommendations have been made there is no solid consensus [17]. Capsaicin cream is a natural chemical derived from a plant that prevents substance P (chemo-mediator that helps transmission of pain to the central nervous system from the periphery) from re-accumulating in the peripheral sensory nerves, providing analgesia [16]. Nerve blocks are used initially for diagnosis, and may also be used for treatment; however, repetition is often necessary since nerve blocks only provide temporary relief. Nerve blocks can be done using blind techniques, ultrasound guidance, and CT guidance. Imaging aids in targeting the correct region and therefore increasing the accuracy and effectiveness of the block.

The next step in the treatment of genitofemoral neuralgia should pharmacologic therapy fail to manage the symptoms is an ablative technique. If that should also fail, then surgery (neurectomy) is considered. Although there is no clear consensus on a recommended surgical time, a period of 6 months to 1 year of conservative management is suggested prior to proceeding with surgery. The definition of chronic pain consists of persistent symptoms for more than 3–6 months after the injury; therefore, at least 6 months is recommended. The logic for the recommended time frame is to allow for enough time for the major inflammatory process to decrease so that a neuropathic pain syndrome can be identified separate from inflammation post injury (or post trauma/post surgery), as well as attempted medical management [6, 17]. The ablative techniques are available at this time including radiofrequency ablation and cryoablation, and both are done with imaging, usually CT, fluoroscopy, or ultrasound guidance.

Radiofrequency ablation utilizes high temperatures targeted at a small area immediately in the vicinity of the target nerve to cause neurolysis and diminish the pain. It has been shown to provide long-term pain relief, without damaging the perineurium or epineurium, and therefore minimizing the risk of neuroma formation. The effect is not always long term, however, and repetition may be necessary [9]. Radiofrequency ablation has been utilized in the management of chronic pain since 1974 when continuous radiofrequency (CRF) ablation was used. Pulsed radiofrequency (PRF) was first used with clinical results in 1998 and was developed in an effort to minimize tissue damage that was a known complication with CRF. Other known complications of CRF included neuritis-like reactions, deafferentation pain, and possibly even motor deficits. CRF works by creating coagulation necrosis of the target tissue by a probe which heats to between 60 and 80 °C, causing tissue destruction [7]. Coagulative necrosis is a type of necrosis characterized by the maintenance of tissue architecture [31]. At temperatures of 60 °C and greater, coagulation necrosis occurs instantaneously, At 50–52 °C, necrosis occurs in approximately 4–6 min [15], and at 45 °C, in about 20–30 min [31]. CRF utilizes a high-frequency alternating current (between 200 and 1200 Hz) and creates well-circumscribed lesions. The degree of tissue destruction is dependent on the duration of radiofrequency, the size of the electrode tip, the temperature of the tissue, and also the distance of the tissue from the electrode tip. CRF differs from PRF in that PRF uses short high-voltage bursts of radiofrequency current, approximately 20 ms per burst, with a silent phase in between bursts to allow for heat to be decreased. The tissue temperature remains less than 42 °C. Theoretically, as well as based on a few histopathologic studies looking at dorsal root ganglia in rats, PRF causes only temporary endoneurial edema, and in general causes less tissue destruction than CRF while still allowing for pain relief. Due to the lower temperatures utilized by PRF, the mechanism of action involves a temperature-independent mechanism consisting of a rapidly changing electrical field, which alters the transmission of pain signals via a specific pathway [7]. Evidence to support such a theory is unfortunately inconclusive, so the mechanism of efficacy of PRF still remains unclear. It is known that PRF current reversibly disrupts transmission of the pain impulse of C fibers (small unmyelinated pain fibers) selectively with larger pain fibers being preserved in their myelin sheaths [18]. The efficacy of PRF in treating chronic pain has been described in multiple different pain syndromes including inguinal pain and orchialgia. In one study, three patients with groin pain or orchialgia underwent PRF after diagnostic nerve blocks. Each patient had PRF to either the genitofemoral or the ilioinguinal nerve for 120 s at 42 °C, and had total resolution of symptoms at the 6-month follow-up [10]. In another study, one patient with chronic orchialgia attributed to the genital branch of the GFN underwent ultrasound-guided PRF ablation of the genital branch and was symptom-free during activity and at rest at the 7-month follow-up [34]. CT-guided radiofrequency and phenol ablation were demonstrated by Parris et al. in 2010 (with only short-term relief in pain).