Continuing Education Activity

Ilioinguinal neuralgia is a frequent cause of pain in the lower abdomen and the upper thigh and is commonly caused by entrapment or injury of the nerve after lower abdominal surgeries. The ilioinguinal nerve is responsible for motor innervation of the transverse abdominis and internal oblique muscles. It provides sensory innervation to a region of the upper anteromedial thigh. In males, it also supplies sensory innervation to the anterior surface of the scrotum and root of the penis and in females, supplies sensory innervation to the labia majora and mons pubis. Male or female patients with ilioinguinal neuralgia may complain of pain, paresthesia and abnormal sensation in the area supplied by the nerve. This activity explains when ilioinguinal neuralgia should be considered on differential diagnosis and reviews the proper evaluation and management of this condition. This activity stresses the role of the interprofessional team in caring for patients with this condition.

Objectives:

• Explain when ilioinguinal neuralgia should be included on differential diagnosis.
• Describe the evaluation of ilioinguinal neuralgia.
• Summarize the management options for ilioinguinal neuralgia.
• Review some interprofessional team strategies for improving care coordination and communication to advance the management of ilioinguinal neuralgia and improve outcomes.

Introduction

Ilioinguinal neuralgia is a frequent cause of pain in the lower abdomen and the upper thigh. The ilioinguinal nerve is a mixed nerve originating from the anterior rami of T12 and L1 nerve roots. It emerges near the lateral border of the psoas major muscle and goes inferior through the anterior abdominal wall, being sub-peritoneal and anterior to the quadratus lumborum muscle until it reaches the iliac crest. Then the ilioinguinal nerve goes through the transverse abdominis and the internal oblique muscles. It becomes superficial by passing through the superficial inguinal ring anterior to the spermatic cord. It gives motor innervation to the transverse abdominis and the internal oblique muscles. Also, it carries sensory information from the anterior surface of the scrotum and root of the penis in males or labia majora and mons pubis in females, and a small area of the upper anteromedial thigh. Because of its long course, entrapment or injury of the nerve after lower abdomen surgeries is common. Male or female patients can complain of pain, paresthesia, and abnormal sensation in the area supplied by the nerve.

Diagnosis of ilioinguinal neuralgia requires a careful history, physical examination, electrophysiologic studies, and ultrasound examination. Treatment of the ilioinguinal neuralgia includes conservative measures as oral analgesics, anticonvulsants, rehabilitation as electro-analgesic currents, and myofascial release. If conservative measures do not control symptoms, ultrasound-guided block, hydro-dissection, or radio-frequency ablation of the nerve can provide satisfactory symptomatic relief. Resistant cases may require neurectomy.[1][2][3]

Etiology

A) Traumatic:

1. Iatrogenic (during surgery)[2][4][5]:

• Inguinal hernia repair
• Traumatic trochar from laparoscopic surgery
• Appendectomy and hysterectomy
• Abdominoplasty
• Orchiectomy

2. Accidental[6]:

• Blunt abdominal trauma
• Femoral catheterization
• Lower external oblique aponeurosis disruption (hockey players) 

3. Stretch trauma:

• Pregnancy

B) Idiopathic - nerve entrapment at:

• The paravertebral area
• Iliac crest
• Rectus border muscle
• Inguinal region

These nerve entrapments often result from abnormalities in the musculoaponeurotic connective tissue (tight fascial planes).[7] 

Epidemiology

Ilioinguinal neuralgia is a common cause of chronic lower abdominal and anterior pelvic pain. The ilioinguinal neuralgia is not uncommon following the surgical repair of an inguinal hernia, and it is rarely because of stretch or entrapment neuropathy.[8]

Pathophysiology

A) In cases of nerve trauma, partial or complete transection can occur; in the cases of a total transection of the nerve, Wallerian degeneration may follow. 

B) In cases of nerve entrapment:

• At the site of the entrapment, there is compression and flattening of the nerve.
• Proximal to the site of the entrapment, there is swelling of the nerve.

The net result is progressive ischemia of the nerve, potentially leading to the following[9]:

• Pain
• Loss of function
• Impaired sensory input
• Hair loss and trophic changes in the anterior surface of the scrotum and root of the penis in males or labia majora and mons pubis in females
• A small area of the upper anteromedial thigh and weakness of the muscles supplied by the ilioinguinal nerve

History and Physical

Entrapment neuropathies are common disorders which lead to significant disability. Correct diagnosis is essential for proper management. History taking and physical examination are a cornerstone in the diagnosis of the ilioinguinal neuralgia. Patients of ilioinguinal neuralgia complain of pain (mostly postsurgical) in the lateral aspect of the iliac fossa, lower abdomen, and upper thigh, as well as abnormal sensation in the cutaneous distribution of the nerve (hyperesthesia or hypoesthesia). The pain is often burning in nature, continuous, and may radiate to the scrotal or inguinal region.

On examination, there is tenderness on palpation 1 inch medial and inferior to the anterior superior iliac spine and impaired sensation along the sensory distribution of the nerve. Complete neurologic examination is mandatory to exclude genitofemoral neuralgia, lumbosacral radiculopathy, and plexopathy.[10]

Evaluation

1. Ultrasound examination: Tracing the nerve starting from the psoas major border is difficult because of the small size of the nerve and the depth of the nerve, especially in obese patients. It is easy to trace the nerve at the iliac crest down to the superficial inguinal ring and see the cause of the entrapment (for example, the scar of surgery). An ultrasound-guided block can confirm a diagnosis of the ilioinguinal neuralgia.[11]

2. Electrophysiologic studies: The benefit of the electrophysiologic examination for the diagnosis of the ilioinguinal nerve injury is questionable. Electrophysiologic studies are more directed to exclude lumbar radiculopathy and plexopathy.[3]

3. Magnetic resonance imaging: performed on the lumbosacral spine to exclude lumbar radiculopathies.

4. A common method of confirming the diagnosis is by infiltrating the area with a local anesthetic and determining if the patient has relief from pain.

Treatment / Management

There are multiple strategies to treat chronic groin pain.[12][13] The pain of neuropraxia is typically temporary and disappears with time. Sometimes, the chronic groin pain persists and interferes with the activities of daily living.[5]

A) Conservative treatment[14][15]:

Lifestyle modification:

• Walking, stooping, or hyperextension of the hip joint exacerbates chronic groin pain - the recumbent position and flexion of the hip joint and thigh relieves pain.

Painkillers:

• Includes non-steroidal anti-inflammatory drugs (NSAIDs), opioids, antiepileptics, and antidepressants

Rehabilitation:

• Transcutaneous electric nerve stimulation, myofascial release, and acupuncture can control symptoms of the ilioinguinal neuralgia.

B) Ultrasound-guided nerve block[14]:

Aim:  interruption of the neuronal transmission leading to temporary pain relief.

Substances injected:  local anesthetics (with or without steroids) or neurolytic agents.

Principal: injection of these chemicals prevent neuronal transmission through ilioinguinal nerve fibers either by blocking membrane ion channels or by denaturation of axon proteins.

Technique: 

1. Patient position: supine
2. Use a linear probe with a frequency ranging from 5 to 10 MHz
3. Place the probe transversely and start scanning from the anterior superior iliac spine.

The nerve lies between transversus abdominis and internal oblique muscles lateral to the inferior epigastric artery and the iliohypogastric nerve. Operators introduce a needle from lateral to medial using an in-plane approach to place the injectate accurately around the nerve.

C) Surgical treatment[15][5]:

Indications: Persistent, intractable pain after the failure of conservative measures.

Principal: Neurectomy involves identifying and dissecting the nerve proximal to the area of trauma, or if possible, the entire length of the nerve.

The approach can be open or laparoscopic.

Differential Diagnosis

Differential diagnosis includes:

• Lumbar radiculopathy
• Lumbar plexopathy
• Genitofemoral  neuralgia
• Ilio-hypogastric neuralgia
• Inguinal hernia
• Hydrocele
• Varicocele.

A thorough history, physical examination, electrophysiologic studies, ultrasound examination, magnetic resonance imaging, and individual nerve block can help differentiate the exact cause of the lower abdomen and groin pain.[16]

Prognosis

Chronicity of the pain after injury or entrapment of the ilioinguinal nerve is not uncommon. But, the majority of patients respond well to nerve block or surgical neurectomy. However, some patients may continue to have burning pain for months or years. This pain is often unaffected by the usual analgesics; patients may require management by a pain specialist in such cases.

Complications

1. Complications of the non-steroidal anti-inflammatory drugs[17][18][19]:

• Gastritis
• Peptic ulcer
• Nephropathy
• Hepatotoxicity
• Hypertension
• Bleeding/thrombosis

2. Complications of the central painkillers as gabapentin[20]:

• Ataxia
• Dizziness
• Fatigue
• Somnolence
• Fever
• Nystagmus
• Peripheral edema

 3. Complications of the nerve block[21][22][23][24]:

• Peripheral nerve injury or vascular injury.
• Transient femoral anesthesia 
• Bowel perforations
• Pelvic hematomas

Ultrasound guidance lowers the incidence of the above-mentioned complications.

• Ilioinguinal blocks require a small volume of injection; the possibility of local anesthetic toxicity is less frequent.

 4. Complications of the neurectomy[5]:

• Infection
• Hematoma
• Seroma
• Testicular edema
• Tingling

Deterrence and Patient Education

• Reduction of body weight
• Avoid positions and activities that precipitate pain

Enhancing Healthcare Team Outcomes

Prevention of the ilioinguinal neuralgia is possible; surgeons should work to avoid injury of the nerves near the field of the surgery and use meshes that don't induce fibrotic reactions. The diagnosis and treatment of ilioinguinal neuralgia need an interprofessional approach. Collaboration between physiatrists, neurologists, pain physicians, and surgeons should direct a proper approach to therapy to improve prognosis. Nurses and therapists should teach patients a healthy lifestyle to minimize pain and improve the activities of daily living. The pain can be severe, and it is best to involve the pain specialist and the pharmacist early. The pharmacist should educate the patient on pain medications and their adverse effects. The pain specialist may have to try a variety of medical and non-medical measures to obtain pain relief. While some patients do obtain pain relief, a significant number of patients will have chronic pain that can affect the quality of life. Because the pain may lead to depression and anxiety, a mental health nurse should counsel the patient.