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Yuyi You, Chenyu Wang, Sidong Liu, Stuart L Graham, Alexander Klistorner; Anterograde microstructural changes along the visual pathways in optic neuritis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):615. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The human visual pathway is characterised by its retinotopic architecture and, therefore, represents a unique model to study transneuronal degeneration. The aim of this longitudinal cohort study is to investigate changes in the visual pathways secondary to optic neuritis (ON).
Pre- and post-gadolinium T1, T2 and diffusion MRI scans were performed in 79 consecutive relapsing-remitting multiple sclerosis (MS) patients. Patients were followed up for 3 years with MRI, Fourier-domain optical coherence tomography (OCT) scans and multi-focal visual evoked potential (VEP) recordings. 20 healthy subjects were also recruited as controls.
The optic radiations (OR) were generated using diffusion MRI and co-registered with T2 lesions. 30 patients who did not present OR T2 lesions during the follow-up were included in further analysis. 14 patients had a history of ON, while the other 16 patients did not have previous ON attacks. At baseline, a significant anisotropic increase of water diffusion was detected in the OR with perpendicular (radial) diffusivity (RD, measure of myelin integrity) alteration extending more posteriorly compared to parallel (axial) diffusivity (AD). An increase of AD in the anterior OR segments was only found in ON patients, but not in non-ON patients. In contrast to the AD changes, RD increase was seen along the entire length of OR in ON patients, but only observed in the anterior part of OR close to the lateral geniculate nucleus in non-ON patients. During the follow-up, a significant progressive RD increase was found in ON patients, mainly localised in the anterior OR segments. By contrast, no longitudinal RD changes were seen in non-ON patients. Base on the retinotopic projections of the visual pathways, we further analysed the correlation between the increase of RD in ON patients and corresponding ON-related retinal ganglion cell (RGC) loss in the retina by asymmetry analysis. We observed a significant association (p=0.03; r=-0.433) between relative RGC loss in the retina and RD increase in the OR.
This study suggests transneuronal changes along the visual pathways at the macroscale level, however the fact that myelin pathology precedes axonal loss in this process indicates the significant involvement of glial components and the co-called ‘transsynaptic’ degeneration might not be purely transsynaptic at the microscale level.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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