Chronic meralgia paresthetica and neurectomy

Abstract

Objective: To understand the pathologic and clinical correlates of patients with chronic meralgia paresthetica (MP) undergoing lateral femoral cutaneous nerve (LFCN) neurectomy.Methods: A retrospective cohort approach was utilized to identify 7 patients undergoing LFCN neurectomy for intractable pain. Control autopsied LFCN was obtained. Clinical, radiologic, and electrophysiologic features were reviewed.Results: In identified cases, preoperative symptoms included severe lateral thigh pain and numbness. The duration of symptoms prior to surgery ranged from 2 to 15 years. Body mass index (BMI) varied from 20 kg/m 2 to 44.8 kg/m 2 (normal-morbidly obese), with 6 out of 7 patients being obese. No patients were diabetic. Focal nerve indentation at the inguinal ligament was seen intraoperatively and on gross pathology in 4 of 7 cases. Multifocal fiber loss, selective loss of large myelinated fibers, thinly myelinated profiles, regenerating nerve clusters, perineurial thickening, and subperineurial edema were seen. None of these features were observed in control nerve. Morphometric analysis confirmed loss of large myelinated fibers with small and intermediate size fiber predominance. Five patients had varying degrees of intraneural and epineurial inflammation. Six of 7 reported improved pain after neurectomy, sometimes dramatic. Meralgia paresthetica (MP) has been found to be relatively common, with an incidence of 32.6-43 per 100,000 patient-years.1,2 The incidence is greatest in older persons (55-64 years) with elevated body mass index (BMI), which supports the theory that mechanical compression plays a role.1 However, a strong association between diabetes and MP was also found, which was not explained by the increase in BMI alone, suggesting that diabetes may be an independent risk factor for MP. Specifically considered in the lateral femoral cutaneous nerve (LFCN), pathologic mechanisms of MP are (1) compression at the inguinal ligament from obesity; (2) injury susceptibility related to elevated blood sugars; or (3) an inflammatory or autoimmune mechanism as occurs in diabetic and nondiabetic lumbosacral plexitis, which commonly affects the femoral nerve.

Low back pain due to superior cluneal nerve entrapment: A clinicopathologic study

“…At human nerve compression sites, a thickened perineurium, subperineurial edema, Renaut bodies, nerve enlargement due to an increase in endoneurial connective tissue, marked decrease in large fibers, and an increase in thin myelinated fibers have been reported . Our pathologic findings were very similar to those made at peripheral nerve compression sites.…”

Anatomical considerations on transposition of the lateral femoral cutaneous nerve

“…Important thereby to realize is that the lateral femoral nerve is a pure sensory nerve (contrary to most other entrapped nerves) and that, although neurectomy causes numbness of the anterolateral part of the thigh, we have found that most patients are not bothered by this numbness (de Ruiter et al, 2012). In addition, histopathologic analysis of resected nerve segments in patients with persistent symptoms of meralgia paresthetica has shown that several intraneural changes have occurred (Berini et al, 2014), which might explain why neurolysis sometimes fails to relieve symptoms.…”

Skin biopsy in assessing meralgia paresthetica

“…Imaging studies, including ultrasound and magnetic resonance neurography (MRN), may be useful, but further confirmatory studies are needed, plus MRN is not widely available. Although LFCN pathology in chronic meralgia paresthetica has been reported to show selective loss of large myelinated fibers, a functional study has suggested small‐fiber involvement . Similar to NCS, skin biopsy can differentiate sensory neuropathy from radiculopathy, as IENFD can be affected in sensory neuropathy but should not be affected by preganglionic root lesions.…”