R. Graham Vanderlinden and Rajiv Midha

Case Presentation

There is no “typical” case history, though the following illustrates some of the difficulties experienced by both patient and physician in dealing with this entity. A 31-year-old woman developed intermittent right lower quadrant pain following a miscarriage. Three years later, a right inguinal hernia was repaired and the symptoms subsided. The hernia recurred 5 months later following childbirth. The hernia was repaired again a year later, and at the same time the ilioinguinal nerve was explored and scar tissue removed. Her pain was not relieved but progressed in severity and radiated to the anteromedial thigh and sometimes to the posterior superior iliac spine. There was constant discomfort but, at times, the pain was sharp and she graded it as 8 out of 10 on the visual analog scale. The severe pain was precipitated by coitus, and she was unable to lie supine without flexing her hips. Assessment by three gynecologists, two laparoscopic examinations, abdominal ultrasound, barium enema, and colonoscopy showed no abnormalities. Five years after the second hernia surgery the patient presented to us with ongoing severe pain. Several medications had failed to provide significant benefit.

The cutaneous branches of the lumbar plexus give rise to the iliohypogastric, ilioinguinal, and genitofemoral nerves, the lateral femoral cutaneous nerve of the thigh, and the obturator nerves.

The iliohypogastric is a motor and sensory nerve arising from the T11, T12, and L1 nerve roots. It emerges from behind the lateral edge of the psoas muscle and pierces the transversus abdominis muscle above the iliac crest. Its anterior branch runs forward between the internal oblique muscle and the external oblique aponeurosis, which it penetrates to supply the skin above the pubis. Its posterior branch supplies an area of the buttock just posterior to the iliac crest.

The ilioinguinal nerve is also a mixed nerve arising primarily from L1 but also receiving branches from T12 that emerge behind the psoas muscle below the iliohypogastric nerve. It passes obliquely across the quadratus lumborum and iliac muscles and perforates the transverse abdominal and internal oblique muscles medial to the anterior superior iliac crest. It runs along the inguinal canal and emerges through the external ring. It provides sensation to the upper medial aspect of the thigh and the base of the scrotum and labia. In several hundred cases studied by Moossman, a “normal” course of the ilioinguinal nerve was seen in only 60%, with the remainder having the ilioinguinal nerve as a branch of the iliohypogastric or genitofemoral nerves.

The genitofemoral nerve arises from L1 and L2 and consists mainly of sensory fibers with a motor branch to the cremasteric muscle (efferent component of the cremasteric reflex). It travels obliquely through and over the psoas muscle, emerging in the retroperitoneal space opposite the L4 vertebral body. It divides into the genital (external spermatic) and femoral (lumboinguinal) branches, which travel separately behind the ureter and across the base of the broad ligament. The genital branch crosses the lower end of the external iliac artery and enters the inguinal canal through the internal ring. It follows the spermatic cord or round ligament and supplies sensation to the scrotum or labia and medial upper thigh. The femoral branches descend lateral to the external iliac artery behind the inguinal ligament; passing through the fascia lata, they enter the femoral sheath where they lie lateral to the femoral artery. These branches supply sensation to the upper anterior thigh.

Characteristic Clinical Presentation

Diagnostic Tests

Unfortunately, electrical and imaging tests are not useful in elucidating the diagnosis of iliohypogastric and ilioinguinal neuropathy. If suspected on clinical grounds, local blocks of the ilioinguinal–iliohypogastric nerves with bupivacaine (or another local anesthetic with an intermediate duration of action) at the trigger point medial to the anterior superior iliac spine help confirm the diagnosis. A similar block of the genitofemoral nerve at the external ring may help to differentiate between these two neuralgias. The addition of steroids does not produce prolongation of pain relief. Differential paravertebral blocks of the T11, T12, L1, and L2 nerve roots are also useful in some patients to substantiate the neuropathic nature of the pain.

Management Options

The initial approach may be conservative, using one or a combination of physical modalities, psychotherapy, and pharmacotherapy. Many of these patients have already visited a pain clinic and been treated with various medications. If not, a course of tricyclic agents is worthwhile, such as amitriptyline or nortriptyline. Other medications that may be beneficial include anticonvulsant agents such as carbamazepine (Tegretol, Novartis Pharmaceuticals Corp., East Hanover, NJ) and gabapentin (Neurontin, Pfizer, Inc., New York, NY).

For those patients with an obviously painful or entrapped ilioinguinal or iliohypogastric nerve, especially where a nerve block has been successful in ameliorating pain, a peripheral nerve surgical procedure is warranted. Intraoperative management is dictated by the findings at surgery, with the two main options being neurolysis or neurectomy.

Surgical Treatment

Decompression or Neurolysis

The inguinal area was explored by means of an incision beginning superior and medial to the anterior superior iliac spine, extending parallel to the inguinal ligament, and ending at the pubic tubercle. The external oblique aponeurosis was opened parallel to its fibers down to the external inguinal ring. The ilioinguinal and iliohypogastric nerves were identified and dissected along their courses from the internal oblique to the external ring and rectus sheath, respectively. There was considerable anatomical variability in the course of these nerves. If the nerve was obviously entrapped by tendinous bands at the point of exit from the internal oblique muscle a decompression or neurolysis was done.

Successful pain relief was achieved in 34% of patients, whereas 50% of cases were failures and 16% were lost to follow-up. Three of these patients required repair of an unsuspected direct hernia at the time of surgery.

Neurectomy

Neurectomy was done in patients who had failed decompression or where previous surgery had invested the nerve in extensive scarring.

Successful pain relief was obtained in 60% of patients, failures were observed in 38%, and one patient was lost to follow-up.

Dorsal Root Ganglionectomy

This procedure was offered to the remaining patients who failed the foregoing procedures (˜20% of initial total), and demonstrated good relief of pain from paravertebral blocks. The microsurgical resection of the sensory components of T11, T12, and L1 nerve roots was done through a paraspinal muscle-splitting incision ˜1 cm lateral to the lateral portion of the intervertebral foramina. Permanent anesthesia in the groin area was produced, but in four patients it was subsequently necessary to extend the ganglionectomies up to T9 and T10 or down to L2. The success rate was 50%, whereas failure to produce pain relief was observed in 30%. Twenty percent of patients were lost to follow-up.

Discussion