eMedicine Specialties > Physical Medicine and Rehabilitation > Lower Limb Musculoskeletal Conditions

Meralgia Paresthetica

Author: Christopher Luzzio, MD, Clinical Assistant Professor, Department of Neurology, University of Wisconsin at Madison
Contributor Information and Disclosures

Updated: Mar 18, 2009

Introduction

Background

Meralgia paresthetica (MP) is pain or an irritating sensation felt over the anterior or anterolateral aspect of the thigh due to injury, compression, or disease of the lateral femoral cutaneous nerve (LFCN). (See image below and Image 1.) Early investigators of MP include Bernhardt, who first described the condition in 1878; Hagar, who attributed the pain to compression of the LFCN; and Roth, who coined the term meralgia paresthetica (thigh pain).

Pathophysiology

The lateral femoral cutaneous nerve (LFCN) is formed by the fusion of the posterior branches of the second and third lumbar nerves. This purely sensory nerve traverses the retroperitoneum around the lateral circumference of the ileum to the inguinal ligament (IL). Just medial to the anterosuperior iliac spine (ASIS), the LFCN passes underneath the IL and enters the anterior thigh beneath its fascia (see Image 1). Ordinarily, a few centimeters distal to the IL, the LFCN divides into anterior and posterior branches. Tributaries of these branches perforate thigh fascia and receive sensory information from portions of the associated dermatomes L2-L3. Typically, this area encompasses the anterior lateral thigh from just below the hip to above the knee. Variations in the anatomy of the LFCN, such as splitting by the inguinal ligament, are hypothesized to predispose it to neuropathic processes.^1,2

Nerve entrapment can occur at 3 potential sites, including (1) beside the spinal column, (2) within the abdominal cavity as the nerve courses along the pelvis, and (3) as the nerve exits the pelvis. The last site is the most common; there, nerve entrapment may involve the sartorius muscle, or it may be caused by simple compression superficially near the iliac crest and ASIS by tight clothing or trauma.

The angulation of the LFCN across the iliac crest results in varying compressive forces with postural repositioning. One opinion is that fibrous bands within the fascia subject the LFCN to deleterious tensile forces. The relatively superficial trajectory of the LFCN as it enters the thigh compartment makes it extremely prone to injury due to compression against underlying bone.

The LFCN is subject to systemic processes that can detrimentally affect any peripheral nerve. Diabetes mellitus, for example, can result in diffuse or focal neuropathies, especially in nerves, such as the LFCN, that are subject to excessive compressive forces.

Movement of the hip changes angulation and tension of the nerve, which can affect symptoms. For example, hip extension may increase angulation and tension on the LFCN, and flexion can decrease these forces.

A Brazilian study involving 14 patients with meralgia paresthetica (MP) and 14 control subjects found evidence that not only are the large myelinated nerve fibers of the LFCN affected in MP, but the small fibers may be as well, with the small fibers suffering a partial loss of function and causing painful symptoms.³ The investigators suggested that this is particularly true in individuals who have had MP for a longer period of time.

Frequency

United States

Considered uncommon but not rare, meralgia paresthetica (MP) is probably underrecognized. Notably, 3 cases are reported per 10,000 general clinic patients. Also, it occurs in an estimated 7-35% of patients referred for leg discomfort. Up to 20% of patients with MP have bilateral symptoms.

Mortality/Morbidity

Isolated meralgia paresthetica (MP) secondary to compression or injury of the nerve unrelated to major trauma or to systemic or malignant processes is not associated with mortality or significant morbidity.

Sex

Meralgia paresthetica is more common in males than in females.

Age

Meralgia paresthetica is observed in all age groups, but the condition most commonly occurs in middle-aged adults.

Clinical

History

A patient whose meralgia paresthetica (MP) is idiopathic or is caused by mechanical injury near the IL may describe paresthesias or dysesthesias within the cutaneous distribution of the lateral femoral cutaneous nerve (LFCN).

• Paresthesias are abnormal sensation perceptions, such as tingling, numbness, burning, itching, cold, and warmth, that are not triggered by obvious cutaneous physical stimulation.
• Dysesthesias are distorted perceptions of ordinary tactile or painful stimuli (eg, burning, tingling, itchiness).²
• Changes in posture or prolonged sitting or standing may cause a fluctuation of symptoms. The discomfort may resolve spontaneously and reappear.
• The appearance of MP symptoms may accompany other factors, such as a motor vehicle accident, pregnancy, surgery, weight loss, and weakness. The examiner should inquire about these associations, because LFCN pathology has several etiologies, some of which are benign and others of which require urgent investigation.

Physical

Isolated lesions of the lateral femoral cutaneous nerve (LFCN) result only in abnormalities on sensory examination. Reduced perception of pinprick or dysesthesias within the receptive fields of the LFCN is typical. Often, the clinician can plot the cutaneous boundaries of the LFCN with an ink marker on the thigh of a person with meralgia paresthetica (MP). A careful neurologic examination is necessary so that it is not assumed that the patient has a benign form of MP. Hip extension may elicit symptoms, while flexion may relieve them.

• If the neurologic examination reveals abnormalities in reflexes, power, gait, or sensation outside the boundaries of the LFCN, then processes concurrently affecting other nerves are considered. For example, reduced patellar reflex, weak leg extension, and symptoms of MP indicate possible pathology within the lumbar plexus, such as a space-occupying lesion. This condition is a plexopathy, not MP.
• Application of pressure over the LFCN at the IL may elicit tenderness or exacerbate the symptoms of MP. This Tinel sign supports localization of the pathologic process to that region.

Causes

Several processes can affect the lateral femoral cutaneous nerve (LFCN) detrimentally along its course, causing sensory dysfunction perceived within its cutaneous distribution.⁴ The processes cited below cause classical meralgia paresthetica (MP; lesion of the LFCN at IL) and pathologies that produce symptoms of MP due to lesions at various points along the LFCN. In many of these diagnoses, additional neurologic symptoms, signs, and examination findings may be present that would indicate LFCN pathology along with other nerve injuries (eg, lumbar or lumbosacral plexopathy, multiple level radiculopathy).

• Trauma
  • Acute compression of the LFCN at the IL from seatbelt forces in rapid deceleration during motor vehicle accidents
  • Pelvic fracture
• Iatrogenic - LFCN injury has been reported in the following surgical procedures:
  • Iliac crest bone grafting
  • Pelvic osteotomy
  • Shelf operations for acetabular insufficiency
  • Inguinal lymph node dissection
  • Appendectomy
  • Total abdominal hysterectomy
• Retroperitoneal subacute mechanical - The following processes may cause a plexopathy:
  • Tumor invasion
  • Hemorrhage
  • Abscess
• Obstetric/gynecologic
  • Endometriosis - MP pain recurs and abates with menses.
  • Fetal compression during the second and third trimesters
• Subacute and chronic mechanical compression or stretching at the IL - The following situations can cause classical MP:
  • Tight-fitting garments⁵
  • Braces, trusses
  • Carpenter's belts
  • Belts for flag carriers
  • Obesity
• Other mechanical causes, including the following:
  • Reservoir for intrathecal medications placed in the right lower abdominal quadrant (personal account)
  • Ascites
  • L2, L3 root compressions
  • In multiple radiculopathies (pathology at the nerve root), muscle groups, including lumbar paraspinal muscles supplied by the L2 or L3 nerve roots, are weak or show denervation changes on electromyogram (EMG) needle examination.
• Metabolically and immunologically related causes, including the following:
  • Diabetes
  • Plexitis
• Infectious conditions - Those associated with MP include herpes zoster.
• Idiopathic causes

• Search for CME/CE on This Topic »

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• Nerve Entrapment Syndromes (Neurosurgery)