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Neurology > Electromyography and Nerve Conduction Studies
Meralgia Paresthetica
Article Last Updated: Mar 27, 2007
AUTHOR AND EDITOR INFORMATION
Section 1 of 9  
Author: Elizabeth A Sekul, MD, Department of Neurology, Associate Professor, Medical College of Georgia
Elizabeth A Sekul is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Child Neurology Society
Editors: Aashit K Shah, MD, Associate Professor of Neurology, Wayne State University; Program Director, Clinical Neurophysiology Fellowship, Department of Neurology, Detroit Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Neil A Busis, MD, Chief, Division of Neurology, Department of Medicine, University of Pittsburgh Medical Center - Shadyside, Clinical Associate Professor, Department of Neurology, University of Pittsburgh School of Medicine; Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Author and Editor Disclosure
Synonyms and related keywords:
lateral femoral cutaneous mononeuropathy, entrapment of lateral femoral cutaneous nerve, paresthesias of upper lateral thigh area, numbness of upper lateral thigh area, meralgia paresthetica, obesity, contained iliopsoas hemorrhages, neoplasms in the retroperitoneal space, pregnancy, tight clothing
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.
Pathophysiology
Reviewing the anatomy of the LFCN is essential for understanding the mechanism of its injury. 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. This is the most common site of entrapment.
Frequency
United States
The exact frequency of meralgia paresthetica is unknown, but the condition is not rare.
Race
No racial predilection is known.
Sex
No gender proclivity is known.
Age
Lateral femoral cutaneous neuropathies have been reported in all age groups.
History
- 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.
- Walking or standing may aggravate the symptoms; sitting tends to relieve them.
Physical
- 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.
- Motor strength in the involved leg should be normal.
Causes
- Pregnancy, tight clothing, and obesity predispose to compression of the nerve at the inguinal ligament.
- Lying in the fetal position for prolonged periods also has been implicated.
- Meralgia paresthetica is more common in diabetics than in the general population.
- 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.
Femoral Mononeuropathy
Other Problems to be Considered
Lumbosacral disk syndromes
Other Tests
- 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.
Medical Care
Removing the cause of compression is the best therapy.
- In some patients, this entails weight loss and wearing loose clothing.
- Most patients with meralgia paresthetica will have mild symptoms that respond to conservative management.
- 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.
- 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.
Prognosis
- The paresthesias typically resolve slowly over time, but the numbness in the distribution of the LFCN may persist.
| Media file 1:
Anatomy of the lateral femoral cutaneous nerve. |
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| Media file 2:
Sensory distribution of the lateral femoral cutaneous nerve. |
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Meralgia Paresthetica excerpt Article Last Updated: Mar 27, 2007
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