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L. Mnatsakanyan, F.N. Ross–Cisneros, V. Carelli, A.A. Sadun; Degeneration of Peripheral Nerves in Leber's Hereditary Optic Neuropathy (LHON) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):661.
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Purpose:LHON is a pathological disorder characterized by profound bilateral loss of central vision due to a point mutation in the mtDNA. Nerves of the brachial plexus in LHON have not been characterized histologically. This study was designed to investigate possible qualitative and quantitative changes in a peripheral nerve of a patient with LHON as compared to normal controls. Methods: We obtained at necropsy, a specimen of brachial plexus from a patient with a history of blindness from LHON carrying the 3460 mutation without known clinical features of peripheral neuropathy. Control tissue was also obtained from age – matched cadavers. The tissue was fixed by immersion in a buffered aldehyde solution, then processed for embedding into plastic blocks. For histological examination semi thin cross– sections were obtained, stained with p–phenylenediamine(PPD) for myelin. The nerves were evaluated by a Zeiss Standard light microscope coupled to a Spot digital camera that allowed for capturing the images and manually counting the fibers per area. Results:Extensive axonal degeneration of the large heavily myelinated fibers was found in all fascicles during examination. The magnitude of axonal degeneration was calculated as a ratio of normal axons per degenerated profile. One degenerated profile consists of elements from many degenerated axons. We observed range axons: degenerated profile from between 2:1 to 5:1. There were focal areas within the LHON fascicles demonstrating high densities of axonal degeneration. The frequency of degeneration in control nerves was 10:1, which is consistent with reports in the literature. Conclusions:This study shows histopathological evidence of sub–clinical involvement of peripheral nerve in the brachial plexus in a patient with LHON. Axonal turnover in peripheral nerves appeared to be at a rate about 3 times higher in patients with LHON as a result of the mtDNA mutation as compared to normal aging in age–matched controls.
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