White Matter Hyperintensities of Presumed Vascular Origin: Current Understanding of Development and Progression

White matter hyperintensities (WMH) of presumed vascular origin are among the most common MRI manifestations of cerebral small vessel disease and are a major contributor to vascular contributions to cognitive impairment and dementia. Although WMH have traditionally been attributed to chronic ischemia resulting from small vessel pathology, the biological mechanisms underlying their development and, more importantly, their progression remain incompletely understood. Recent advances in longitudinal neuroimaging, quantitative MRI, pathology, genetics, and physiological imaging have substantially expanded our understanding of WMH progression, making this an appropriate time to evaluate current concepts and synthesize emerging evidence.

We review contemporary evidence regarding the biological processes implicated in WMH development and progression, including hypertension and vascular risk factors, acute ischemic injury, chronic hypoperfusion, blood-brain barrier (BBB) dysfunction, endothelial activation and vascular inflammation, arterial stiffness, intracranial artery dolichoectasia (IADE), altered cerebral fluid dynamics and genetic susceptibility. Longitudinal studies demonstrate that WMH exhibit dynamic trajectories characterized by progression, stability, and partial regression, indicating that lesion evolution is not uniformly irreversible. Pathological and advanced neuroimaging studies show that WMH represent heterogeneous tissue injury involving demyelination, axonal loss, gliosis, interstitial fluid accumulation, and microvascular abnormalities. Hypertension and blood pressure variability are consistently associated with greater WMH burden and progression, whereas baseline WMH burden is the strongest predictor of future lesion expansion. Acute ischemic lesions detected by diffusion-weighted imaging contribute to, but account for only a minority of WMH progression. Longitudinal studies evaluating cerebral perfusion, BBB permeability, inflammation, arterial stiffness, IADE and cerebral fluid dynamics have yielded variable findings but, together with genetic evidence, support roles of BBB leakage, vascular inflammation, chronic hypoperfusion, arterial and extracellular-matrix remodeling, and impaired interstitial fluid clearance in WMH progression.

Emerging evidence supports a paradigm in which WMH are viewed as a dynamic manifestation of progressive neurovascular dysfunction rather than the consequence of chronic ischemia alone. Current data suggest that early neurovascular injury evolves into a potentially self-reinforcing process characterized by persistent BBB disruption, vascular inflammation, chronic hypoperfusion, altered fluid dynamics, and recurrent ischemic injury, collectively contributes to WMH progression. Future multimodal longitudinal studies integrating cerebral hemodynamics, neurovascular function and intracranial arterial remodeling will be essential to understand WMH progression.