Diffusion tensor free water MRI predicts progression of FLAIR white matter hyperintensities after ischemic stroke

White matter free water mediates the associations between placental growth factor, white matter hyperintensities, and cognitive status

INTRODUCTION

Placental growth factor (PlGF) may regulate cerebrovascular permeability. We hypothesized that white matter interstitial fluid accumulation, estimated via magnetic resonance imaging (MRI) free water (FW), would explain the associations between elevated PlGF, white matter hyperintensities (WMH), and cognitive impairment.

METHODS

MarkVCID consortium participants ≥55 years old with plasma PlGF and brain MRI were included. We tested cross-sectionally whether FW mediated the associations between PlGF and WMH, or PlGF and cognition, measured using the Clinical Dementia Rating (CDR) scale and an executive function (EF) composite (Uniform Data Set version 3 [UDS3]-EF).

RESULTS

For 370 participants (mean age 72), a higher PlGF was associated with higher FW, higher WMH, and higher CDR, but not UDS3-EF. Higher FW was associated with higher WMH, higher CDR, and lower UDS3-EF. FW explained 26% of the association between PlGF and CDR and 73% of the association between PlGF and WMH.

DISCUSSION

Elevated PlGF may contribute to WMH and cognitive impairment through white matter FW accumulation.

CLINICAL TRIAL REGISTRATION

NCT06284213 HIGHLIGHTS: PlGF is a promising blood-based biomarker for vascular cognitive impairment. In MarkVCID, higher PlGF was associated with accumulated white matter FW on MRI. FW mediated the association between higher PlGF and MRI-visible white matter injury. FW mediated the association between PlGF and worse CDR scale. PlGF may contribute to cognitive dysfunction via accumulated interstitial fluid.

Distinguishing Early from Late Mild Cognitive Impairment Using Magnetic Resonance Free-Water Diffusion Tensor Imaging

Mild Cognitive Impairment (MCI) is a transitional stage between normal aging and Alzheimer's disease. Differentiating early MCI (EMCI) from late MCI (LMCI) is crucial for early diagnosis and intervention. This study used free-water diffusion tensor imaging (fw-DTI) to investigate white matter differences and voxel-based correlations with Mini-Mental State Examination (MMSE) scores. Data from the Alzheimer's Disease Neuroimaging Initiative included 476 healthy controls (CN), 137 EMCI participants, and 62 LMCI participants. Significant MMSE differences were found between the CN and MCI groups, but not between EMCI and LMCI. However, distinct white matter changes were observed: LMCI showed a higher f-index and lower fw-fractional anisotropy (fw-FA) compared to EMCI in several white matter regions. These findings indicate specific white matter tracts involved in MCI progression. Voxel-based correlations between fw-DTI metrics and MMSE scores further supported these results. In conclusion, this study provides crucial insights into white matter changes associated with EMCI and LMCI, offering significant implications for future research and clinical practice.

Blood-brain barrier disruption and increased free water are associated with worse cognitive performance in patients with chronic cerebrovascular disease

Progression of cerebral small vessel disease (CSVD) is associated with cognitive decline. Blood-brain barrier disruption (BBBD) and fluid extravasation to the interstitial space may contribute to progression of white matter hyperintensities (WMH). We hypothesized that increased free water (FW) would colocalize with BBBD and relate to cognitive performance. Patients with ischemic stroke/TIA at least 3 months prior with at least early confluent WMH were studied cross-sectionally with the Montreal Cognitive Assessment (MoCA), diffusion tensor imaging, and dynamic susceptibility contrast imaging. White matter (WM) was segmented into WMH, WMH penumbra, and normal appearing white matter (NAWM). Colocalization of elevated FW and BBBD and their associations with MoCA performance were evaluated. 58 patients were included (mean age 69, 36 % female). Higher BBBD colocalized with elevated FW. Elevated FW in all white matter, NAWM, WMH penumbra, and WMH lesions was associated with lower MoCA score. Increased BBBD in all WM, NAWM, and WMH penumbra was associated with lower MoCA. In WMH penumbra, both elevated FW and increased BBBD were independently associated with lower MoCA. We found agreement between 2 different biomarkers implicated in the pathogenesis of CSVD that independently demonstrated association with cognitive performance when measured in the area of postulated disease activity.

Subtle white matter intensity changes on fluid-attenuated inversion recovery imaging in patients with ischaemic stroke

Leukoaraiosis is a neuroimaging marker of small-vessel disease that is characterized by high signal intensity on fluid-attenuated inversion recovery MRI. There is increasing evidence from pathology and neuroimaging suggesting that the structural abnormalities that characterize leukoaraiosis are actually present within regions of normal-appearing white matter, and that the underlying pathophysiology of white matter damage related to small-vessel disease involves blood-brain barrier damage. In this study, we aim to verify whether leukoaraiosis is associated with elevated signal intensity on fluid-attenuated inversion recovery imaging, a marker of brain tissue free-water accumulation, in normal-appearing white matter. We performed a cross-sectional study of adult patients admitted to our hospital with a diagnosis of acute ischaemic stroke or transient ischaemic attack. Leukoaraiosis was segmented using a semi-automated method involving manual outlining and signal thresholding. White matter regions were segmented based on the probabilistic tissue maps from the International Consortium for Brain Mapping 152 atlas. Also, normal-appearing white matter was further segmented based on voxel distance from leukoaraiosis borders, resulting in five normal-appearing white matter strata at increasing voxel distances from leukoaraiosis. The relationship between mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter and leukoaraiosis volume was studied in a multivariable statistical analysis using linear mixed modelling, having normal-appearing white matter strata as a clustering variable. One hundred consecutive patients meeting inclusion and exclusion criteria were selected for analysis (53% female, mean age 68 years). Mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter was higher in the vicinity of leukoaraiosis and progressively lower at increasing distances from leukoaraiosis. In a multivariable analysis, the mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter was positively associated with leukoaraiosis volume and age (B = 0.025 for each leukoaraiosis quartile increase; 95% confidence interval 0.019-0.030). This association was found similarly across normal-appearing white matter strata. Voxel maps of the mean normalized fluid-attenuated inversion recovery signal intensity on normal-appearing white matter showed an increase in signal intensity that was not adjacent to leukoaraiosis regions. Our results show that normal-appearing white matter exhibits subtle signal intensity changes on fluid-attenuated inversion recovery imaging that are related to leukoaraiosis burden. These results suggest that diffuse free-water accumulation is likely related to the aetiopathogenic processes underlying the development of white matter damage related to small-vessel disease.