Physical Medicine and Rehabilitation for Meralgia Paresthetica Workup
- Author: Christopher Luzzio, MD; Chief Editor: Consuelo T Lorenzo, MD more...
Indicated laboratory and radiologic studies for lateral femoral cutaneous nerve (LFCN) pathology depend on the suspected etiology and clinical impression. Meralgia paresthetica (MP) caused by obvious benign compressive forces requires no further investigation; however, the following scenarios might necessitate more testing:
Magnetic resonance imaging (MRI) to investigate the lumbar plexus
Serum tests for diabetes
Radiography for possible pelvic fracture or cancer
Computed tomography (CT) scanning for retroperitoneal hemorrhage in patients who have undergone anticoagulation therapy
A study by Suh et al indicated that ultrasonography can aid in the diagnosis of MP by determining the cross-sectional area of the LFCN. The investigators suggested that, based on the values derived from the patients in the study with unilateral MP (n=23), as well as from the controls (n=12), the cross-sectional area’s optimal cutoff value for a diagnosis of MP was 5 mm2.
Electromyography is very helpful for ruling out radiculopathy, plexopathy, generalized polyneuropathy, or other neuropathic causes for the symptoms. Nerve conduction studies and somatosensory evoked potentials of LFCN have shown abnormalities in patients with MP, but these tests are unreliable and are not necessary for the diagnosis.
Caution: Discomfort over the anterolateral thigh may not be representative of LFCN injury. Referred pain can be caused by neoplastic invasion of nearby femoral or pelvic bone. In the author's experience, the pain associated with a neoplasm or bone fracture is deep, boring, and severe. MP discomfort is superficial, with fluctuating dysesthesias, paresthesias, and cutaneous hypersensitivity; it is neuropathic in quality and usually is not disabling.
See the list below:
For classical meralgia paresthetica (MP), conservative therapy may be initiated without the necessity for invasive procedures. The diagnosis (ie, an MP secondary to trauma, irritation, or compression of the lateral femoral cutaneous nerve [LFCN] near the IL) can be verified by injecting a small quantity of lidocaine at the point of their intersection or at the point of tenderness. The discomfort should resolve transiently.
Diagnosis of LFCN often is verified by nerve conduction studies. The LFCN is stimulated antidromically 1-2 cm medial to the ASIS above the IL; the response is recorded 12-20 cm distally over the lateral thigh. Excessively thick soft tissue makes surface stimulation technically difficult or inadequate; the examiner may choose needle stimulation instead. Right and left LFCNs are compared. Study findings are considered abnormal if there are significant side-to-side differences; there may be no response or a 50% drop in amplitude compared with the contralateral nerve. If there is no recordable response on the asymptomatic side, the results obtained when testing the symptomatic thigh are not interpretable. Asymptomatic individuals have widely variable LFCN action potentials in conduction studies.
Carai A, Fenu G, Sechi E, et al. Anatomical variability of the lateral femoral cutaneous nerve: findings from a surgical series. Clin Anat. 2009 Jan 27. 22(3):365-370. [Medline].
Otoshi K, Itoh Y, Tsujino A, et al. Case report: meralgia paresthetica in a baseball pitcher. Clin Orthop Relat Res. 2008 Sep. 466(9):2268-70. [Medline].
Moritz T, Prosch H, Berzaczy D, et al. Common anatomical variation in patients with idiopathic meralgia paresthetica: a high resolution ultrasound case-control study. Pain Physician. 2013 May-Jun. 16(3):E287-93. [Medline].
Schestatsky P, Llado-Carbo E, Casanova-Molla J, et al. Small fibre function in patients with meralgia paresthetica. Pain. 2008 Oct 15. 139(2):342-8. [Medline].
Knight RQ, Schwaegler P, Hanscom D, et al. Direct lateral lumbar interbody fusion for degenerative conditions: early complication profile. J Spinal Disord Tech. 2009 Feb. 22(1):34-7. [Medline].
Moucharafieh R, Wehbe J, Maalouf G. Meralgia paresthetica: a result of tight new trendy low cut trousers ('taille basse'). Int J Surg. 2008 Apr. 6(2):164-8. [Medline].
Suh DH, Kim DH, Park JW, et al. Sonographic and electrophysiologic findings in patients with meralgia paresthetica. Clin Neurophysiol. 2013 Jul. 124(7):1460-4. [Medline].
Alberti O, Wickboldt J, Becker R. Suprainguinal retroperitoneal approach for the successful surgical treatment of meralgia paresthetica. J Neurosurg. 2008 Oct 31. [Medline].
van Eerten PV, Polder TW, Broere CA. Operative treatment of meralgia paresthetica: transection versus neurolysis. Neurosurgery. 1995 Jul. 37(1):63-5. [Medline].
Emamhadi M. Surgery for Meralgia Paresthetica: neurolysis versus nerve resection. Turk Neurosurg. 2012. 22(6):758-62. [Medline].
de Ruiter GC, Wurzer JA, Kloet A. Decision making in the surgical treatment of meralgia paresthetica: neurolysis versus neurectomy. Acta Neurochir (Wien). 2012 Oct. 154(10):1765-72. [Medline].
Tagliafico A, Serafini G, Lacelli F, Perrone N, Valsania V, Martinoli C. Ultrasound-guided treatment of meralgia paresthetica (lateral femoral cutaneous neuropathy): technical description and results of treatment in 20 consecutive patients. J Ultrasound Med. 2011 Oct. 30(10):1341-6. [Medline].
Fowler IM, Tucker AA, Mendez RJ. Treatment of meralgia paresthetica with ultrasound-guided pulsed radiofrequency ablation of the lateral femoral cutaneous nerve. Pain Pract. 2012 Jun. 12(5):394-8. [Medline].
Liveson JA, Ma DM. Lumbar plexus. Laboratory Reference for Clinical Neurophysiology. New York, NY: Oxford University Press; 1998. 165-8.
Massey EW. Sensory mononeuropathies. Semin Neurol. 1998. 18(2):177-83. [Medline].
Nahabedian MY, Dellon AL. Meralgia paresthetica: etiology, diagnosis, and outcome of surgical decompression. Ann Plast Surg. 1995 Dec. 35(6):590-4. [Medline].
Streiffer RH. Meralgia paresthetica. Am Fam Physician. 1986 Mar. 33(3):141-4. [Medline].
Travell JG, Simons DG. Tensor fasciae latae muscle and sartorius muscle. Myofascial Pain and Dysfunction: The Trigger Point Manual for the Lower Extremities. Baltimore, Md: Williams & Wilkins; 1999. vol 2: 230-2.