Surgery for Meralgia Paresthetica Workup

Updated: Jul 08, 2019
  • Author: Ira Kornbluth, MD, MA, FAAPMR; Chief Editor: William L Jaffe, MD  more...
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Workup

Laboratory Studies

Laboratory evaluation for diabetes and thyroid disorders may be warranted in some cases. Although meralgia paresthetica is not an obscure condition, the diagnosis may be elusive because it is based largely on clinical grounds.

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Imaging Studies

Imaging studies generally are not of any specific benefit in diagnosing meralgia paresthetica, except in excluding differential diagnoses. If a mass lesion or fracture is suspected as the cause of this entity, appropriate imaging may be warranted.

A study by Suh et al found ultrasonography (US) to be useful as a supplemental diagnostic tool for meralgia paresthetica that could provide information about the morphology and course of the lateral femoral cutaneous nerve (LFCN). [18]  A study by Hanna et al found preoperative US-guided wire localization to be useful for minimizing the time needed to find the LFCN, as well as for identifying anatomic abnormalities that might not be apparent otherwise. [19]

A small study by Chhabra et al found 3-Tesla magnetic resonance neurography to be reliable and accurate for the diagnostic evaluation of meralgia paresthetica. [20]

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Electrodiagnostic Evaluation

An electrodiagnostic evaluation, including electromyography (EMG) and nerve conduction studies, is often unnecessary but may be helpful as an adjunct to the history and physical examination in confirming the diagnosis of meralgia paresthetica and establishing a prognosis.

Nerve conduction tests can help determine the severity of the nerve injury by comparing the result with standard values and with the contralateral side. The smaller the amplitude relative to the contralateral side, the greater the nerve dysfunction. Frequently, recording needles are required for sensory testing to ensure adequate responses. If very low amplitudes are obtained, an average of responses may be used.

Comparing nerve conduction study findings on the affected side with those from the contralateral side provides some indication of the nature and severity of the nerve injury. Studies may be confounded by the fact that many patients have bilateral involvement. The LFCN can be stimulated as it exits the pelvis, with potentials recorded distally, or it can be stimulated distally, with recordings made proximally. US-guided nerve conduction study of the LFCN has been described. [21]

Needle EMG testing may be performed to evaluate for other pathologic conditions, such as radiculopathy or other peripheral neuropathies. In meralgia paresthetica, needle EMG findings should be normal.

Somatosensory evoked potentials (SSEPs) have been found to be less accurate than nerve conduction studies.

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Histologic Findings

In a study of 39 consecutive patients with persistent symptoms of meralgia paresthetica, de Ruiter et al attempted to quantify histopathologic changes inside the LFCN and to determine the extent to which these changes were present after primary (n = 29) vs secondary neurectomy (n = 10). [22]  Intraneural changes studied included (1) thickening of perineurium, (2) deposition of mucoid, and (3) percentage of collagen. Analysis was performed proximal to, at, and distal to the previous site of compression. Possible correlations with symptom duration and patient body mass index (BMI) were considered.

Intraneural changes were found consistently in all 39 cases, with no significant difference between primary and secondary neurectomy groups. [22] The occurrence of intraneural changes was weakly correlated with the duration of symptoms, but the association was not statistically significant. These findings suggested that the intraneural changes noted in persistent meralgia paresthetica may be largely irreversible.

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