This study group from Italy explored the contribution of local and distant mechanisms associated with optic radiation (OR) damage in MS. Using 102 MS patients and 11 controls, they derived diffusion tensor MRI probability maps of the OR. They assessed OR normal appearing white matter (NAWM) damage and topographical distribution of OR damage using quantitative and voxel-wise analyses, considering the influence of previous optic neuritis (ON+) and T2 OR lesions (T2 OR+).
The researchers found that OR NAWM diffusivity abnormalities were more severe in ON+ patients than in patients without previous optic neuritis (ON-) and T2 OR+ versus T2 OR- patients. They found that damage to the anterior portions of the ORs were more severe in ON+ than ON- patients. T2 OR+ patients experienced a more distributed pattern of DT MRI abnormalities along the ORs when compared to controls and T2 OR- patients. The DT MRI abnormalities along the ORs were characterised by increased mean diffusivity, axial diffusivity and radial diffusivity and decreased fractional anisotrophy, which suggests myelin damage and axonal loss. OR damage correlated with OR T2 lesion volume, visual dysfunction and optic nerve atrophy. Therefore, trans-synaptic degeneration secondary to optic nerve damage and Wallerian degeneration due to local T2 lesions contribute to OR damage in MS.
Authors: Rocca MA, Mesaros S, Preziosa P
Source: Mult Scler. 2013 Apr 9. [Epub ahead of print]
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