Table 1.
Radiological and Pathologic Features of Spectrum of Small Vessel Disease in AD Dementia
| Clinical features | SVD feature | Imaging marker | Key pathologic features | Degree of change in AD (compare aging or neurological controls)∗ |
|---|---|---|---|---|
| Stroke(s)/vascular origin | Silent infarcts | WMHs on T2W, FLAIR, ↑ high signal | Unclear | ++ |
| Transient Ischemic attacks | WMHs on DWM; high signal | Unclear | + | |
| White matter attenuation | WMHs (pvWMH, dWMH), WM atrophy in CAA; high signal | Demyelination in deep WM; axon damage | +++ | |
| Lacunar infarcts | Hyperintense lesions on T2W/FLAIR | Lacunes (<1.5 cm) in BG, thalamus, WM | ++ | |
| Cortical Infarcts | Hyperintense lesions on T2W/FLAIR | Cortical infarcts | + | |
| Microinfarcts | Tiny hyperintense lesions on T2W (3T, 7T) | Microinfarcts (<0.5 cm) in GM and WM | +++ | |
| Microbleeds | T2∗W or GRE signal lobar and deep bleeds; hypointense lesions on T2W | Hemosiderin deposits in cortex (CAA) and subcortical structures (hypertensive) | ++ | |
| Intracerebral hemorrhages | Hyperintense on CT; hypointense lesions on T2W | ICH, microaneurysms | + | |
| Cerebral siderosis | Hypointense signal on GRE | SAH | + | |
| Vascular pathologies | Perivascular spaces (enlarged Virchow-Robin spaces) | Hyperintense rounded lesions on T2W/FLAIR | PVS in WM; GM of BG | ++ |
| Intracranial atherosclerosis | Unclear | Occasional microatheromas in branches of MCA, ACA | + | |
| Arteriolosclerosis | Unclear | Moderate-severe arteriolosclerosis | +++ | |
| CAA | Posterior WMHs, lobar microbleeds | Moderate-severe CAA in cortex; predominance in occipital lobe | +++ | |
| Vascular Function | CBF | Resting CBF | Parietal, temporal lobes, BG | +++ |
| BBB function | Permeability on MRI (contrast agents, Gd) | EC damage, ↓ capillary density | +++ | |
| PVW | Phase contrast MRI; pulse sequence with retrospective peripheral pulse gating sequences | Arteriosclerotic vessels; collagen fibers | +++ | |
| Autonomic function (hypoperfusion) | Tilt table, carotid sinus supersensitivity (OH, CSH) | WMLs, arteriolosclerosis, microinfarcts in BG | ++ |
Neuroimaging and pathologic changes involving SVD in AD.
ACA, anterior cerebral artery; AD, Alzheimer disease; BG, basal ganglia; CAA, cerebral amyloid angiopathy; CBF, cerebral blood flow; CSH, carotid sinus hypersensitivity; DWM, deep white matter; dWMH, deep white matter hyperintensities; EC, endothelial cell; FLAIR, fluid attenuated inversion recovery; Gd, gadolinium; GM, grey matter; GRE, gradient echo; ICH, intracerebral hemorrhage; MCA, middle cerebral artery; MRI, magnetic resonance imaging; OH, orthostatic hypotension; PVS, perivascular space; pvWMH, periventricular white matter hyperintensities; PVW, pulse wave velocity; SAH, subarachnoid hemorrhage; SVD, small vessel disease; WM, white matter; WMH, white matter hyperintensities; WML, white matter lesion.
Changes found in AD type of dementia above and beyond normally aging healthy subjects. Arrow (↑) indicates increase. Scale of change means scores: +, mild (1); ++ moderate (2), severe +++ (3). Microhemorrhages may be caused by leakage by two mechanisms: microaneurysms and rupture of walls due to deposition of fibrillar proteins or iron.28