University of British Columbia
Physics and Astromony

Author Of 1 Presentation

Imaging Late Breaking Abstracts

LB1271 - MRI insights into myelin damage in Susac Syndrome (ID 2169)

Abstract

Background

Susac’s Syndrome (SuS) is a rare autoimmune endotheliopathy of the brain, retina and cochlea that mimics multiple sclerosis (MS). Lesions presumed to be microinfarcts classically involve the corpus callosum (CC). While one brain biopsy reported demyelination, and MRI studies have shown reduced fractional anisotropy in the CC, the specific processes underlying SuS pathology are not yet clear. Myelin water imaging (MWI) and diffusion basis spectrum imaging (DBSI) can provide information about microstructural changes occurring in SuS. MWI provides a quantitative measurement of myelin, termed the myelin water fraction (MWF). DBSI yields various physiologically relevant metrics characterized by water diffusion: the apparent diffusion coefficient (ADC) which relates to overall tissue damage; fractional anisotropy (FA), which decreases with white matter (WM) damage; and radial diffusivity (RD) which increases with myelin loss.

Objectives

Determine in vivo WM microstructural changes in Susac Syndrome compared to MS and healthy controls (HC) using MWI and DBSI.

Methods

Participants included 7 SuS patients following the proposed European Susac Consortium diagnostic criteria (mean age 43.3y (30-78y), 6F), 10 MS patients (mean age 43.2y (26-70y), 9F) and 10 HC (MWI: 44y (27-64y), 9F, DBSI: 35.9y (22-47y), 5F). 3T MRI included MWI (48-echo 3D GRASE sequence), DBSI (9 b-values, 0-1500 s/mm2, 99 directions) and a 3DT1 for anatomical reference. The CC and global WM (non-lesional tissue) were segmented and registered using FSL and the JHU atlas. One-way ANOVA with Tukey correction compared CC and global WM between groups.

Results

CC: SuS MWF (0.09±0.01) was lower than MS (0.11±0.02, p=0.03) and trending lower than HC (0.11±0.02, p=0.07). SuS ADC (0.84 ± 0.08 x 10-3μm2/ms) was higher than MS (0.73±0.04 x 10-3μm2/ms, p<0.001) and controls (0.71±0.04 x 10-3μm2/ms, p<0.001). SuS FA (0.82±0.02) was lower than HC (0.86±0.02, p= 0.02). SuS RD was higher (0.27±0.03 x 10-3μm2/ms) than HC (0.21±0.01 x 10-3μm2/ms, p=0.004) and trending higher than MS (0.23±0.05 x 10-3μm2/ms, p=0.05).

Global WM: ADC and RD findings in the Global WM were similar to CC, i.e. ADC and RD were significantly higher in SuS compared to MS and HC (all p<=0.03). However, MWF and FA was insignificantly different between the groups.

Conclusions

We report the first use of MWI in SuS. Both CC and the global WM showed non-lesional myelin damage, which was more severe than MS.

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