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The pathology of multiple sclerosis involves the gray and white matter regions of the brain and spinal cord often
characterized by various combinations of demyelination, inflammatory infiltration, axonal degeneration, and later gliosis
in chronic lesions. While acute and chronic white matter lesions are well characterized and easily identified, evidence
indicates that the CNS of MS patients may be globally altered, with subtle abnormalities found in grossly normal
appearing white matter (NAWM) with histochemical stains and magnetic resonance imaging only indicating a general
alteration in tissue composition at best. Thus, the prototypical acute inflammatory lesion may merely represent the most
obvious manifestation of a chronic widespread involvement of the CNS, which is difficult to examine reliably. The
current study deals with the microstructure and biochemistry of demyelination, remyelination and axonal loss in various
regions in post-mortem human MS brain, especially NAWM areas around more typical acute and chronic lesions. The
myelin sheath, neuroglia and perivascular spaces were investigated through changes in the intrinsic molecular vibrational
signatures of lipid biochemistry using a novel, label-free Coherent anti-Stokes Raman Scattering (CARS) microscope.
The biochemistry of myelin lipids can be probed by detecting subtle changes to phospholipids and the intra-molecular
disorder of their fatty acid acyl chains, various oxidation products and general protein contributions. NAWM regions
surrounding pathological MS lesions were shown to reveal abnormalities despite morphological classifications indicating
otherwise. CARS data were correlated with immunohistochemical stains and lipophilic dyes. Spectral data were
analyzed using a unique non-linear algorithm, which allows quantification and classification through gated parameters
and displayed through bivariate histograms. Our CARS microscopy system provides high-resolution, detailed
morphological and unique biochemical information regarding CNS pathology in human MS examples and may be
applicable to a broad range of other white matter centric neurological disorders.
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