Morphological MRI phenotypes of multiple sclerosis differ in resting-state brain function

Area of Science:

• Neuroimaging
• Neurology
• Functional Connectivity

Background:

• Multiple sclerosis (MS) is characterized by diverse pathological changes, including white matter lesions and grey matter damage.
• Distinct MRI-defined phenotypes in MS may exhibit differential impacts on brain function and connectivity.

Purpose of the Study:

• To investigate resting-state functional connectivity (FC) differences in the sensorimotor network (SMN) across distinct multiple sclerosis (MS) MRI-phenotypes.
• To compare FC between MS groups with predominant white matter damage (WMD) and grey matter damage (GMD), and healthy controls (HC).

Main Methods:

• Utilized resting-state functional MRI (fMRI) and independent component analysis (ICA) to analyze FC in the SMN.
• Categorized 180 MS patients into WMD (high T2-lesion load, high normalized brain volume) and GMD (low T2-lesion load, low normalized brain volume) groups.
• Compared FC patterns between WMD, GMD, and 37 age-matched HC.

Main Results:

• WMD patients exhibited increased FC across all SMN sub-units compared to GMD patients.
• WMD patients showed increased FC in the central SMN (leg area) compared to both GMD patients and HC.
• In the WMD group, higher Expanded Disability Status Scale (EDSS) scores and T2-lesion load correlated with reduced SMN connectivity.

Conclusions:

• Distinct morphological MRI-phenotypes in MS are associated with significant differences in brain functional connectivity.
• Focal white matter pathology, rather than global brain atrophy, appears to be a key determinant of altered connectivity in the central SMN.
• Findings support the concept of a disconnection syndrome in MS, where white matter integrity influences network function.