Description

Meralgia paraesthetica comes from the Greek words meros (thigh) and algos (pain).¹ Meralgia paraesthetica is usually an entrapment syndrome of the lateral femoral nerve. It may be iatrogenic after medical or surgical procedures, or result from a neuroma. The segmental origin is L2/L3 and it is a purely sensory nerve with no motor fibres.²

Epidemiology²

An incidence has been estimated at 4.3 per 10,000 person years. The condition is thought to be much rarer in children.³ A study of 20 cases in children and adolescents found that half the patients had bilateral lesions.⁴

Risk factors^2,5

No gender proclivity is known. It may be bilateral. It can occur in pregnancy, obesity, and if there is tense ascites.⁶ It may be a result of trauma, previous surgery or, in some cases, may arise from abduction splints used to treat Perthes' disease, also called Calvé-Legg-Perthes disease. Lying for long periods of time in the fetal position and lying prone after lumbar spine surgery have also been identified as possible causes. Risk factors can arise in the most unlikely scenarios. Recently, a spate of meralgia was found to be due to the body armour worn by American soliders in Iraq.⁷ It occurs more commonly in diabetics than in the general population. Most cases are idiopathic.

History

Entrapment causes burning or numbness down the upper lateral aspect of the thigh. In children and adolescents the presentation is severe pain causing marked restriction of activities.⁴

Examination^2,8

The pain can be reproduced by deep palpation just below the anterior superior iliac spine (pelvic compression) and also by extension of the hip.⁹ There is altered sensation over the anterolateral aspect of the thigh. There is no motor weakness.

Differential diagnosis

Very often the diagnosis is slow to be made. Pain in the lateral thigh can arise from the back, hip or knee.¹⁰ It is important to consider the possibility of the diagnosis and to try deep palpation medial to the anterior superior iliac spine and extension of the hip. Injection with local anaesthetic appears to be a good test.

Other conditions that may need to be ruled out include:⁸

• Diabetic lumbosacral plexopathy.
• Lumbar degenerative disc disease.
• Lumbar facet arthropathy.
• Lumbar spondylolysis and spondylolisthesis.
• Mononeuritis multiplex.
• Neoplastic lumbosacral plexopathy.

Rarely, pressure on the lateral cutaneous femoral nerve can arise from a mass in the retroperitoneal space, e.g. tumours, iliopsoas haemorrhage.²

Investigations^2,8

• The pelvic compression test is highly sensitive, and the diagnosis can often be made with this test alone.⁹
• Injection of the nerve with local anaesthetic will abolish the pain. Find the spot where deep pressure reproduces the pain and infiltrate below there. The nerve is quite superficial.
• Nerve conduction studies may be used before operation.¹¹

Other tests to rule out differential diagnoses might include fasting blood glucose, MRI of the lumbar spine and radiographs for possible pelvic fracture or cancer.

Management^2,8

• In the case of obesity, loss of weight may cure the condition but is not guaranteed. It should resolve after pregnancy and tapping of ascites should help.
• Idiopathic meralgia paraesthetica usually improves with nonoperative modalities, such as removal of compressive agents, non-steroidal anti-inflammatory drugs, anticonvulsants or tricyclics and, if necessary, local corticosteroid injections.¹²
• One study has reported successful use of pulsed radiofrequency neuromodulation.¹³
• Other physical therapies found helpful include transcutaneous electrical nerve stimulation, interferential current and low-intensity phonophoresis.⁸
• One study has reported the use of Kinesio® tape (an elastic strapping used in physical therapies) applied to the area where symptoms were experienced.¹⁴
• If the pain is severe, operative decompression should be considered. A suprainguinal or infrainguinal approach may be used.¹⁵

Prognosis²

Paraesthesia tends to resolve over time but the numbness can persist.

Anatomy

The nerve originates from the L2/L3 segments and travels down, lateral to the psoas muscle. It crosses the iliacus muscle deep to the fascia and then passes through or under the lateral part of the inguinal ligament. It runs superficially and divides into anterior and posterior branches to innervate the lateral thigh. The course of the nerve can be a little variable but usually it can be found about 10-15 mm medial to the anterior superior iliac spine but can occasionally be up to 5 cm medial.¹⁶

Document references

1. Harney D, Patijn J; Meralgia paresthetica: diagnosis and management strategies. Pain Med. 2007 Nov-Dec;8(8):669-77. [abstract]
2. Sekul EA; Meralgia Paresthetica, eMedicine, Aug 2009
3. Fernandez-Mayoralas DM, Fernandez-Jaen A, Jareno NM, et al; Meralgia paresthetica in the pediatric population: a propos of 2 cases. J Child Neurol. 2010 Jan;25(1):110-3. Epub 2009 May 20. [abstract]
4. Edelson R, Stevens P; Meralgia paresthetica in children. J Bone Joint Surg Am. 1994 Jul;76(7):993-9. [abstract]
5. Wheeless C; Lateral Femoral Cutaneous Nerve Wheeless' Textbook of Orthopaedics, 2008
6. Mondelli M, Rossi S, Romano C; Body mass index in meralgia paresthetica: a case-control study. Acta Neurol Scand. 2007 Aug;116(2):118-23. [abstract]
7. Fargo MV, Konitzer LN; Meralgia paresthetica due to body armor wear in U.S. soldiers serving in Iraq: a case report and review of the literature. Mil Med. 2007 Jun;172(6):663-5. [abstract]
8. Luzzio C; Meralgia Paresthetica, eMedicine, Mar 2009
9. Nouraei SA, Anand B, Spink G, et al; A novel approach to the diagnosis and management of meralgia paresthetica. Neurosurgery. 2007 Apr;60(4):696-700; discussion 700. [abstract]
10. Erbay H; Meralgia paresthetica in differential diagnosis of low-back pain. Clin J Pain. 2002 Mar-Apr;18(2):132-5. [abstract]
11. Russo MJ, Firestone LB, Mandler RN, et al; Nerve conduction studies of the lateral femoral cutaneous nerve. Implications in the diagnosis of meralgia paresthetica. Am J Electroneurodiagnostic Technol. 2005 Sep;45(3):180-5. [abstract]
12. Grossman MG, Ducey SA, Nadler SS, et al; Meralgia paresthetica: diagnosis and treatment. J Am Acad Orthop Surg. 2001 Sep-Oct;9(5):336-44. [abstract]
13. Philip CN, Candido KD, Joseph NJ, et al; Successful treatment of meralgia paresthetica with pulsed radiofrequency of the Pain Physician. 2009 Sep-Oct;12(5):881-5. [abstract]
14. Kalichman L, Vered E, Volchek L; Relieving Symptoms of Meralgia Paresthetica Using Kinesio Taping: A Pilot Study. Arch Phys Med Rehabil. 2010 May 27. [abstract]
15. Alberti O, Wickboldt J, Becker R; Suprainguinal retroperitoneal approach for the successful surgical treatment of J Neurosurg. 2009 Apr;110(4):768-74. [abstract]
16. Hospodar PP, Ashman ES, Traub JA; Anatomic study of the lateral femoral cutaneous nerve with respect to the ilioinguinal surgical dissection. J Orthop Trauma. 1999 Jan;13(1):17-9. [abstract]

Acknowledgements