University of Padova

Author Of 1 Presentation

Imaging Poster Presentation

P0625 - Quantitative Susceptibility Mapping in the cortical ribbon of MS patients and its dependence on cortical thinning. (ID 1142)

Speakers
Presentation Number
P0625
Presentation Topic
Imaging

Abstract

Background

Neuropathological examinations of multiple sclerosis (MS) brains indicate sub-pial cortical grey matter (GM) demyelination and damage occurring according to a “surface-in” gradient related to elevated levels of inflammation compartmentalized in sub-arachnoid spaces and meninges. Quantitative susceptibility mapping (QSM) is an MRI technique sensitive to changes in iron or myelin.

Objectives

To test the ability of QSM to detect and localize alterations in cortical iron/myelin content in MS and to investigate possible QSM alterations possibly caused by cortical thinning.

Methods

A group of 105 RR-MS patients (40.7±10.2 y mean±std; m:f 13:92; EDSS median 2 (0 - 6)) and 21 matched healthy controls (HC; 39.5±10.5 y; m:f 8:13) were examined by using 3T MRI 3D-EPI (0.5x0.5x0.5mm), 3D T1w (1x1x1mm) and a 3D FLAIR sequence (1x1x1mm). QSM was computed using a total generalized variation algorithm. T1 lesion filled images were analyzed with Freesurfer to reconstruct WM/GM and pial surfaces. QSM was sampled across the entire cortex with steps of 25% of cortical volume (0%: WM/GM, 100%: pial surface) and projected to the 32k vertices Conte-69 template. Group-wise QSM differences were performed by a permutation-based ANOVA test employing threshold-free cluster enhancement to correct for multiple comparisons (p<0.05 FWE corrected). A vertex-wise cortical thickness (CTh) regressor was used to investigate the impact of cortical thinning on QSM alterations.

Results

Significant differences in QSM showing higher susceptibility in RR-MS than HC were present in majority in cerebral sulci (21, 55 and 55% at 25, 50 and 75%) compared to gyri (9, 37, 38% at 25, 50 and 75%) and in the outer portion of the cortex compared to the inner cortex. The percentage of vertices significantly altered was higher in the outer layer (75%) respect to the inner ones (25%) in several regions, including portions of temporal and parietal lobes, precuneus and para- and post-central sulcus. The use of the CTh regressor, showed significant alterations in the same regions, and revealed further alterations of the cingulate cortex.

Conclusions

Surface analysis of QSM exhibits the presence of increase susceptibility in the cortex of MS patients compared to HC: the alterations are more extended in the outer layers of the cortical ribbon than the inner ones, supporting the hypothesis of a “surface-in” gradient of iron/myelin alterations in the cortex of MS patients. Moreover, these differences were not entirely explained by the presence of cortical thinning.

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