Massachusetts General Hospital

Author Of 1 Presentation

Imaging Poster Presentation

P0543 - Associations between Corpus Callosum Damage, Clinical Disability, and Surface-based Homologous Inter-hemispheric Connectivity in Multiple Sclerosis (ID 1052)

Speakers
Presentation Number
P0543
Presentation Topic
Imaging

Abstract

Background

Axon damage in the corpus callosum (CC) correlates with disability in multiple sclerosis (MS). Surface-based Homotopic Inter-hemispheric Connectivity (sHIC) is a reliable and novel technique that estimates resting state functional connectivity in inter-hemispheric homologous cortical areas. Previously, we demonstrated a correlation between CC atrophy and decreased sHIC.

Objectives

To investigate homologous connectivity in MS and its relationship with clinical disability and CC axonal integrity.

Methods

Multi-shell diffusion and resting state MRI data were collected from 36 MS and 42 healthy control (HC) subjects on an ultra-high gradient CONNECTOM 3T scanner. The CC was segmented into five sections and the cortex was parcellated using the Desikan-Killiany atlas. Probablistic tractography was used to determine structural connectivity between CC segments and the cortex. Axon density, axon diameter, and restricted volume fraction were estimated for each CC segment using the Axcaliber method. sHIC was determined using a surface-based atlas approach to estimate homologous regions. Neurological disability was measured for the MS group using the Expanded Disability Status Scale (EDSS).

Results

A vertex-wise group analysis showed that homologous connectivity was decreased in temporal, parietal, and somatomotor areas in the MS group compared to the HC group (p < 0.001). EDSS scores correlated most strongly with sHIC in the precentral, postcentral, superior temporal, and pericalcarine gyri (r = -0.40, -0.36, -0.34, -0.54; p < 0.05). EDSS scores correlated with the mean sHIC from cortical regions connected to the central CC, posterior CC, and whole CC (r = -0.34, -0.36, -0.34; p < 0.05). In the posterior CC, restricted volume fraction correlated with sHIC in the inferior temporal (r = 0.36, p = 0.03) and superior parietal (r = 0.41, p = 0.01) gyri, and axon density correlated with sHIC in the superior parietal gyrus (r = 0.35, p = 0.04). A vertex-wise general linear model found significant clusters of correlations (p < 0.01) between restricted volume fraction and sHIC in the superior/inferior parietal, superior temporal, and precentral gyri.

Conclusions

Homologous connectivity is reduced in MS. Higher EDSS scores were significantly related to decreased homologous connectivity, notably in the somatomotor area. A structure-function relationship is observed between CC axonal damage, decreased homologous connectivity, and disability in MS.

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