Localized Hypertrophic Mononeuropathy Involving the Tibial Nerve

Abstract

Localized hypertrophic neuropathy (LHN) is a disorder of unknown cause that presents with progressive, predominantly motor weakness in the distribution of a single nerve, with the histological appearance of the "onion bulb" formation. Because of its rarity, the condition is often ignored in the differential diagnosis of mononeuropathy. We report a case of LHN involving the posterior tibial nerve and review the literature.

Localized hypertrophic neuropathy: Magnetic resonance imaging findings and long-term follow-up

“…All of these patients were clinically stable during follow-up, except for 2 who had partial improvement. 7,13 Our experience is similar, demonstrating stabilization for 10 months (patient 1) and 2 1/2 years (patient 2) after resection and sural nerve grafting, and showing partial improvement in a proximal muscle 6 months after neurolysis (patient 4).…”

“…In addition, it is unclear as to whether their patient had the same condition, since their lesion was EMA negative and S100 positive, in contrast to most other cases of LHN. Iyer et al 7 did not find diagnostic abnormalities on MRI, but provided no details of the specific imaging sequences used. In our patients, the primary findings of LHN on MRI were enlargement of the affected nerve or plexus, increased signal on the T2-weighted images, and enhancement with gadolinium contrast material.…”

“…Treatments included resection with sural nerve grafting, 3,8,13 resection with end-to-end anastomosis, 11,15 neurolysis, 7,13 and no treatment (biopsy only). 3,11 The length of follow-up was specified in only some of these patients and ranged from 1 to 48 months.…”

“…The lamellae of the onion bulbs stain for epithelial membrane antigen (EMA), while the centers stain for S100 protein. 1,3,8,13,16,17 Magnetic resonance imaging (MRI) findings have been presented briefly in only a few patients with LHN,7,14,17,18 and descriptions of long-term follow-up are also rare. 3,7,11,13,15 We report 4 patients with LHN.…”

Hypertrophic mononeuropathy

“…In addition to perineurioma there are a number of other onion bulb-shaped neuropathies, some of which are mononeuropathies. 6 Differences in architectural arrangement and degree of cellularity between the perineurial and Schwannian forms of localized hypertrophic mononeuropathy suggest important fundamental differences in the pathogenesis of various forms of onion-bulb mononeuropathies. 2 Pathogenesis of LHN.…”