A window into the brain: multimodal MRI assessment of vascular cognitive impairment

Abstract

Vascular cognitive impairment (VCI) encompasses a diverse range of syndromes, including mild cognitive impairment and vascular dementia (VaD), primarily attributed to cerebrovascular lesions and vascular risk factors. Its prevalence ranks second only to Alzheimer's disease (AD) in neuro diseases. The advancement of medical imaging technology, particularly magnetic resonance imaging (MRI), has enabled the early detection of structural, functional, metabolic, and cerebral connectivity alterations in individuals with VCI. This paper examines the utility of multimodal MRI in evaluating structural changes in the cerebral cortex, integrity of white matter fiber tracts, alterations in the blood-brain barrier (BBB) and glymphatic system (GS) activity, alteration of neurovascular coupling function, assessment of brain connectivity, and assessment of metabolic changes in patients with VCI.

Keywords: diffusion tensor imaging; dynamic functional connectivity; glymphatic system; resting-state functional MRI; structure–function coupling; vascular cognitive impairment.

Figure 1

Pathophysiologic alterations and multimodal MRI assessment system for VCI: individuals diagnosed with VCI may exhibit pathophysiological alterations, including neuronal injury, myelin destruction, axonal loss, dysfunction of the neurovascular unit, oxidative stress-induced damage to neuronal cells, and activation of a neuroinflammatory cascade resulting in the formation of a pro-inflammatory microenvironment within the brain. These changes ultimately contribute to modifications in brain structure, function, metabolism, and connectivity. The advancement of MRI imaging technology has enabled the utilization of multimodal MRI and associated post-processing techniques to effectively delineate alterations in brain structure, function, metabolism, and connectivity. Images were produced using FigDraw software (www.figdraw.com) (DOI: PPARW86662).

Figure 2

Schematic representation of the blood–brain barrier (BBB) and perivascular space (PVS): when the BBB permeability increases and the PVS widens, the rate of passive transport of contrast agent and water molecules from the intravascular to the extravascular space increases; at the same time, decreased aquaporin-4 (AQP-4) in astrocyte foot segments, which decreases the active transport of water molecules within the PVS and also makes the PVS wider and the GS dysfunction. These pathological changes can be characterized by the quantitative parameters of dynamic contrast-enhanced MRI (DCE-MRI) requiring exogenous contrast agent and arterial spin-labeled MRI (ASL) and intravoxel incoherent motion MRI (IVIM) without exogenous contrast agent, respectively. Images were produced using FigDraw software (www.figdraw.com) (DOI: AYSRP3949a).