Multimodal MRI assessment of cerebral small vessel disease-related brain injury in the context of unilateral severe carotid artery stenosis.

PURPOSE: To investigate the transhemispheric effects of unilateral severe carotid artery stenosis (CAS) on brain structure and hemodynamics, and their association with cerebral small vessel disease (CSVD) markers.

METHODS

Fifty-one patients with unilateral severe CAS and 48 matched healthy controls underwent multimodal MRI. Quantified metrics included cortical thickness, white matter hyperintensity (WMH) volume, free water fraction in white matter (FW-WM), peak width of skeletonized mean diffusivity (PSMD), and lateralization index for cerebral blood flow (LI-CBF). Group comparisons, interhemispheric comparisons, partial correlation analyses, and multivariable linear regression models were performed.

RESULTS

Compared with controls, CAS patients exhibited reduced cortical thickness (2.32 ± 0.08 vs. 2.36 ± 0.08 mm, P = 0.015), elevated PSMD (median 2.56 × 10⁻⁴ vs. 2.35 × 10⁻⁴, P = 0.006), increased WMH volume (median 4.65 vs. 2.37 cm³, P < 0.001), higher FW-WM (0.21 ± 0.03 vs. 0.17 ± 0.02, P < 0.001), and pronounced CBF lateralization (P < 0.001). Ipsilateral FW-WM was significantly higher than contralateral FW-WM (P < 0.001). Both FW-WM (β'=0.347, P = 0.019) and PSMD (β'=0.426, P = 0.002) were independently associated with global WMH volume. Age and anterior cerebral artery LI-CBF independently predicted FW-WM and PSMD. Ipsilateral WMH volume (β'=-0.264, P = 0.044) and age (β'=-0.371, P = 0.005) were independently associated with MoCA scores.

CONCLUSION

Unilateral severe CAS induces structural and hemodynamic alterations overlapping with CSVD features. Hemodynamic disturbance is associated with diffuse white matter injury, which may contribute to WMH formation. Multimodal MRI metrics provide imaging evidence linking macrovascular stenosis to CSVD.