Meralgia Paresthetica – Diagnosis and Treatment of Symptoms in the Outer Thigh Near the Hip (Topic: Meralgia Paresthetica)

Meralgia paresthetica is a condition caused by nerve compression involving the lateral cutaneous nerve of the thigh. This nerve supplies sensation to the skin on the front and outer side of the thigh, extending down to approximately the knee.

This region experiences sharp, electric-like shooting pains, which are accompanied by numbness in half of all cases. The knee and lower leg are not affected by meralgia paresthetica. The pain is triggered by an extended hip joint, meaning it occurs primarily while standing. It subsides when the hip joint is bent forcefully.

The nerve affected by meralgia paresthetica is, at most, as thick as a pencil lead. It runs along the floor of the pelvis forward toward the inguinal ligament region. Between the layers of the inguinal ligament, it bends downward toward the skin on the front of the thigh.

The nerve affected by meralgia paresthetica is shown here in red © SciePro | AdobeStock

This bend is the problem: it occurs when the hip joint is extended; when the hip joint is flexed, the bend is eliminated.

Depending on the nerve’s position, the rough edges of the individual tendinous layers of the inguinal ligament can pinch the nerve across its course.

The symptoms of meralgia paresthetica are rare, but the condition was first described by Sigmund Freud, who suffered from it himself. The pain can be extremely intense and mimic a herniated disc with sciatic pain.

The nerve consists exclusively of sensory fibers that

• sensation of touch,
• pain sensation, and
• temperature sensation

to the spinal cord and brain. However, it does not contain motor fibers that control muscles. Therefore, there is never any loss of strength in the leg.

Instead, in meralgia paresthetica, the patient only experiences impairment of these three sensory qualities.

There is virtually no diagnostic imaging test that can confirm involvement of the nerve. It is too small to be visualized on magnetic resonance imaging (MRI).

Nerve conduction velocity measurements performed by a neurologist can facilitate the diagnosis of meralgia paresthetica. The physician compares the conduction velocity between the right and left thighs.

When comparing sensation on the front and outer sides of the thighs,

• abnormal sensations,
• tingling sensations, or
• numbness

be reported.

The best way to confirm meralgia paresthetica is through the following very simple test: The patient should first observe which leg positions or movements easily trigger the pain.

During the examination, the doctor injects an anesthetic directly at the site where the nerve runs, along the inner edge of the anterior superior iliac spine. The doctor then instructs the patient to perform precisely these triggering maneuvers while walking outside.

The patient observes whether the pain occurs during the approximately 2-hour duration of the anesthetic’s effect. If not, this proves that the small nerve is indeed affected by meralgia paresthetica.

Meralgia paresthetica causes pain in the thigh © SENTELLO | AdobeStock

There is no medication available to treat meralgia paresthetica. While repeated corticosteroid injections can be administered at the same site as the test injection described above, the chances of improvement for this pain syndrome are very limited.

Pain management with morphine-like medications is definitely not a long-term solution for treating meralgia paresthetica. Conventional pain relievers (anti-inflammatory drugs) may provide temporary relief at best, but they do not resolve the underlying problem.

Therefore, surgery is necessary to relieve the patient’s symptoms.

However, if a persistent burning pain has already developed in the area on the front and outer side of the thigh, it is too late for meralgia paresthetica surgery. In this case, touching the skin causes additional pain (“neuropathic pain”).

Due to the constant stimulation of the central nervous system (spinal cord) originating from the nerve, changes have already occurred that no longer respond to surgery.

Older Approach to Meralgia Paresthetica Surgery

In the past, meralgia paresthetica surgery involved severing the nerve. On the one hand, this causes the nerve’s innervation area to become numb. On the other hand, the resulting nerve stump can become highly sensitive. After a nerve transection, there is a sharp increase in activity in the nerve cell located near the spinal cord, which enables the nerve cell’s process to regrow peripherally into its former distribution area.

However, after a nerve is severed, the several thousand nerve fibers do not know where to grow back to. As a result, a tangled mass of randomly growing nerve fibers (neuroma) forms at the nerve end.

This cluster of sensory nerve endings is highly sensitive to tissue pressure and can trigger new pain. The brain projects this pain into the nerve’s former distribution area.

For this reason, the nerve should not be severed during surgery for meralgia paresthetica.

Current Approach to Meralgia Paresthetica Surgery

The current goal of meralgia paresthetica surgery is to surgically relieve the compression of the nerve. To do this, the surgeon cuts the portions of the inguinal ligament directly on the inner side of the anterior tip of the iliac crest so that the small nerve is no longer pinched by movements and positioning of the hip joint.

This is achieved through a relatively small incision made directly over the tip of the iliac crest. However, in cases where the abdominal wall contains a significant amount of fatty tissue, it may be necessary to considerably enlarge the incision in order to access the structures of the inguinal ligament and the anterior tendon plate covering the thigh.

Whether laparoscopic surgery can also be applied here and prove effective remains to be seen.

After surgery, wound exudate from inside the pelvic floor may spread under the skin through the small opening created during the procedure. Therefore, a suction drain should remain in the surgical area for up to 3 days. This allows the wound to begin the normal healing process, and healing is not impeded by the accumulation of wound fluid.

Although meralgia paresthetica surgery is theoretically possible on an outpatient basis, it is highly inadvisable due to the need to monitor the wound.

No follow-up treatment is required after meralgia paresthetica surgery. At most, it may be necessary to rest the surgical area.

There are no significant risks associated with meralgia paresthetica surgery.

One potential complication of the decompression procedure is the risk that, in cases of abnormal nerve course, injury or transection may still occur. The result would be complete numbness in the nerve’s distribution area. As described, a neuroma forms at the newly created nerve end. However, such a neuroma causes persistent pain in only 10% of cases. Under certain circumstances, severing the nerve may therefore eliminate the pain after all. 

To prevent wound complications at this site, which is frequently subjected to stress in daily life, prolonged suction drainage is recommended. This should ideally also include inpatient follow-up care.

There are no reliable statistical data on the potential course of meralgia paresthetica without surgery. Consequently, information on the success rate of surgery is also lacking.

However, it is estimated that surgery for meralgia paresthetica leads to a cure in 70 to 80% of cases.

The condition and the procedure are so rare that surgeons can only offer personal opinions regarding success rates.

The problem is that there is no reliable preoperative diagnostic testing available.

Meralgia paresthetica is an exceptionally bothersome and debilitating condition. The diagnosis is made through a test injection and, only secondarily, through diagnostic imaging.

The primary treatment is surgery for meralgia paresthetica, which is a minor and often truly effective procedure. Since the surgical site is constantly subjected to stress during all movements, careful wound monitoring is required; therefore, outpatient treatment carries greater risks of complications than inpatient care.

What is meralgia paresthetica?

Meralgia paresthetica is a condition in which a sensory nerve in the hip region becomes pinched. This causes burning pain, paresthesia, or numbness on the outer thigh.

Which nerve is affected?

The affected nerve is the lateral cutaneous nerve of the thigh (NCFL). It runs beneath the inguinal ligament and provides sensory innervation to the skin of the thigh.

What are the typical causes?

Common causes include tight clothing, obesity, diabetes mellitus, prolonged standing, or an anatomical constriction in the area of the anterior superior iliac spine. Pregnancy or prolonged sitting may also play a role.

How is meralgia paresthetica diagnosed?

The diagnosis is usually made clinically based on the typical symptoms and their location. Ultrasound, MRI, or measurement of sensory nerve conduction velocity may also be used to rule out other causes.

How is meralgia paresthetica treated?

Treatment is usually conservative and includes weight loss, avoiding tight clothing, physical therapy, and pain management. If symptoms persist despite conservative therapy, surgical intervention such as a neurectomy may be considered.