Meralgia Paresthetica 

Updated: Jul 31, 2018
Author: Elizabeth A Sekul, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE 

Overview

Background

A painful mononeuropathy of the lateral femoral cutaneous nerve (LFCN), meralgia paresthetica is commonly due to focal entrapment of this nerve as it passes through the inguinal ligament. Rarely, it has other etiologies such as direct trauma, stretch injury, or ischemia. It typically occurs in isolation. The clinical history and examination is usually sufficient for making the diagnosis. However, the diagnosis can be confirmed by nerve conduction studies. Treatment is usually supportive. The LFCN is responsible for the sensation of the anterolateral thigh. It is a purely sensory nerve and has no motor component.[1]

Pathophysiology

Reviewing the anatomy of the LFCN is essential for understanding the mechanism of its injury (see the images below). The LFCN originates directly from the lumbar plexus and has root innervation from L2-3. The nerve runs through the pelvis along the lateral border of the psoas muscle to the lateral part of the inguinal ligament. Here, it passes to the thigh through a tunnel formed by the lateral attachment of the inguinal ligament and the anterior superior iliac spine. The crossover into the thigh is the most common site of entrapment. The crossover typically occurs 1 cm medial to the anterior superior iliac spine; however, regional variations are common.[2]

Anatomy of the lateral femoral cutaneous nerve. Anatomy of the lateral femoral cutaneous nerve.
Sensory distribution of the lateral femoral cutane Sensory distribution of the lateral femoral cutaneous nerve.

Epidemiology

Frequency

United States

In the general population, an incidence of 4.3 per 10,000 person years has been reported.

In people with diabetes mellitus, an incidence of 247 per 100,000 patient years has been reported.[3]

Race

No racial predilection is known.

Sex

No gender proclivity is known.

Age

Lateral femoral cutaneous neuropathies are most common during middle age. However, they have been reported in all age groups.

 

Presentation

History

See the list below:

  • When the LFCN is entrapped, paresthesias and numbness of the upper lateral thigh area are the presenting symptoms. The paresthesias may be quite painful.

  • Symptoms are typically unilateral. However, they may be bilateral in up to 20% of cases.

  • Walking or standing may aggravate the symptoms; sitting tends to relieve them.

Physical

See the list below:

  • Examination reveals numbness of the anterolateral thigh in all or part of the area involved with the paresthesias.

  • Occasionally, patients are hyperesthetic in this area.

  • Tapping over the upper and lateral aspects of the inguinal ligament or extending the thigh posteriorly, which stretches the nerve, may reproduce or worsen the paresthesias.

  • Deep palpation just below the anterior superior iliac spine (pelvic compression testing) reproduces the symptoms. A study in 45 patients found that the pelvic compression test had a sensitivity of 95% and a specificity of 93.3% for meralgia paresthetica.[4]

  • Motor strength in the involved leg should be normal.

Causes

See the list below:

  • Pregnancy, tight clothing, and obesity predispose to compression of the nerve at the inguinal ligament.[5, 6, 7, 3] Tool belts worn by carpenters, duty belts worn by policemen, and body armor worn by soldiers may compress the LFCN.[8]

  • Lying in the fetal position for prolonged periods also has been implicated, as has prone positioning after lumbar spinal surgery.[9]

  • Meralgia paresthetica is more common in diabetics than in the general population.[3]

  • Although rare, impingement of the LFCN by masses (eg, neoplasms, contained iliopsoas hemorrhages) in the retroperitoneal space before it reaches the inguinal ligament can cause the same symptoms.

 

DDx

Differential Diagnoses

 

Workup

Other Tests

See the list below:

  • The clinical syndrome is well defined, and further evaluation by electrodiagnostic studies may be unnecessary.

  • Evaluation with nerve conduction studies and needle examination electromyography (EMG) is warranted if no risk factors are identified, if a mass lesion in the retroperitoneal space is suspected, or if back pain also is present.

  • LFCN conduction studies can be technically difficult. When obtained, compare with the asymptomatic side.

  • The EMG should be normal in LFCN lesions, but the test is helpful in ruling out upper lumbar radiculopathy.

 

Treatment

Medical Care

Removing the cause of compression is the best therapy.

  • In some patients, this entails weight loss and wearing loose clothing.[3]

  • Most patients with meralgia paresthetica will have mild symptoms that respond to conservative management.[10]

  • When the pain is severe, a focal nerve block can be done at the inguinal ligament with a combination of lidocaine and corticosteroids. This should temporarily relieve the symptoms for several days to weeks. Ultrasound guidance for the blockade may be beneficial in patients with regional anatomical variations.[11, 12, 13, 14]

  • Neurogenic pain medications such as carbamazepine or gabapentin typically are not as helpful but may be beneficial in rare patients. If medication of this type is required, then surgical decompression should be considered.

Surgical Care

In rare and particularly painful cases that are unresponsive to nerve block, surgical decompression may be warranted. There is no definitive evidence to differentiate outcome comparing neurolysis versus neurectomy.[15]

 

Follow-up

Prognosis

The paresthesias typically resolve slowly over time, but the numbness in the distribution of the LFCN may persist.

 

Questions & Answers