GFAP and cerebral small vessel disease: Pathological analyses of cerebral small vessel disease have shown dense GFAP-immunoreactive astrocytes in periventricular white matter37 and in clusters within the basal ganglia and thalamus, suggesting that plasma GFAP may reflect blood-brain barrier disruptions and proximity to cerebrospinal fluid and the glymphatic system38, linking GFAP to cerebrovascular pathology in SVCI.