Trans-synaptic degeneration along the visual pathway

Abstract

Aim: This cross-sectional study aimed to investigate anterograde and retrograde trans-synaptic degeneration along the visual pathway in patients with optic neuropathies characterised by retinal ganglion cell (RGC) loss. Method: In glaucoma, a relationship between RGC loss and changes in the optic radiation and primary visual cortex were investigated via diffusion tensor imaging (DTI) and MRI cortical thickness analysis respectively. In multiple sclerosis related optic neuritis (MS-ON), optical coherence tomography segmentation was used to examine retrograde changes in the retina following RGC loss. Results: In the MS-ON group, thickening of the retinal inner nuclear layer correlated with RGC loss severity. Retinal microcysts represented the extreme end of this correlation. In the glaucoma group, there were significant abnormalities in the optic radiation DTI parameters. However, there was no decrease in cortical thickness compared to controls, nor a difference in thickness between the regions of V1 connected to the affected and spared areas of the retina. Conclusions: There is a relationship between RGC loss and changes across the visual pathway. Anterior retinal changes may only represent structural damage, but changes in the optic radiation may reflect anterograde spread of damage. The magnitude of these neurodegenerative changes may decline across more synaptic connections.