Functional and structural connectivity substrates of cognitive performance in relapsing remitting multiple sclerosis...

Area of Science:

• Neuroscience
• Medical Imaging
• Cognitive Science

Background:

• Multiple Sclerosis (MS) is a leading cause of chronic CNS inflammation and neurodegeneration, often resulting in cognitive impairment.
• Conventional MRI metrics have limitations in sensitively tracking MS pathophysiology and its link to clinical disability.
• Understanding the relationship between brain network alterations and cognitive deficits in MS is crucial for effective management.

Purpose of the Study:

• To investigate structural and functional brain connectomes associated with neuropsychological (NP) performance in relapsing-remitting MS (RRMS) patients using graph theory.
• To compare brain network characteristics and their correlation with cognitive function between RRMS patients and healthy controls (HC).
• To elucidate the specific roles of structural and functional connectivity in cognitive performance within the MS population.

Main Methods:

• Employed a graph theoretical approach to analyze structural and resting-state functional connectomes.
• Administered a comprehensive NP test battery assessing attention, processing speed, learning, memory, and executive function.
• Compared brain network metrics (graph strength, nodal strength) and their relationship with cognitive scores between RRMS patients (n=33) and matched HC (n=29).

Main Results:

• Structural network alterations, specifically decreased graph strength, were significantly associated with poorer performance in spatial learning/memory and processing speed (SDMT).
• Nodal strength was reduced in all subnetworks in MS patients compared to HC, while functional connectivity showed no group differences at the nodal level.
• Poorer cognitive performance in MS patients correlated with increased functional connectivity but decreased structural connectivity, particularly within the default mode network.

Conclusions:

• Cognitive deficits in even mildly disabled RRMS patients are associated with a loss of structural brain connectivity.
• Increased functional connectivity may represent compensatory or maladaptive mechanisms in response to underlying structural damage.
• These findings highlight the importance of assessing both structural and functional brain networks to understand cognitive impairment in MS.