The influence of visual pathway integrity on primary and higher order visual dysfunction in synucleinopathies

Abstract

Purpose : To identify visual pathway neuroimaging variables (OCT and brain MRI) associated to primary and higher order visual dysfunction in idiopathic Parkinson’s disease (iPD), Lewy Body Dementia (LBD) and E46K-SNCA mutation carriers (E46K-SNCA).

Methods : Cross-sectional study of n=63 patients with synucleinopathies (n=50 iPD, n=8 LBD and n=5 E46K-SNCA) and n=22 age/sex comparable healthy controls (HC). Measures: 1) Retinal OCT (Spectralis): 3 mm ring bilateral average thickness of macula and its layers; 2) Brain MRI (3 Tesla): regional brain thickness and Voxel Based Morphometry (Freesurfer/FSL), visual and frontal cortex spectroscopy (NAA levels) (Tarquin), optic radiations DTI indexes (FA) (FSL) and internal and external connectivity of medial visual component (MVC) in rs-fMRI; 3) Higher order visual function (HOVF) tests with composites for attention, processing speed, construction and memory; 4) Primary visual function (PVF): binocular best-corrected high and low contrast visual acuity (HCVA and LCVA), Pelli-Robson contrast sensitivity (CS) and color vision (Lanthony D-15 Color Test); 5) PD clinical features (UPDRS, disease duration). Statistical analysis: Student's T-test differences between groups, Pearson correlations and linear regressions (SPSS v. 21).

Results : Compared to HC, patients with synucleinopathies had statistically significant (p〈0.05) poorer results in all PVF and HOVF tests/composites, atrophy of ganglion cell-inner plexiform layer complex (GCIPL), inner nuclear layer (INL), lower NAA levels in visual (not in frontal) cortex, regional bilateral atrophy of inferior, middle and superior temporal, fusiform, lingual and middle occipital gyri and left calcarine gyrus. In patients, and not in HC, higher atrophy of inner retina (GCIPL and INL), calcarine cortex, fusiform and lingual gyri and lower rs-fMRI connectivity of MVC with precuneus were significantly associated to poorer performance in HCVA, LCVA and CS, while atrophy of IPL and INL and middle temporal gyrus, and lower rs-fMRI connectivity of MVC with cuneus were significantly associated with poorer performance in HOVF composites.

Conclusions : Primary and higher order visual abnormalities in synucleinopathies are specifically associated to the damage of the retina and visual regions of the brain, supporting the use of visual pathway analysis as a potential biomarker for neurodegeneration in synucleinopathies.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.