Figure 6

Diagram suggesting the morphological changes that lead to enlargement of WM perivascular spaces. A: Under normal conditions, the brain’s interstitial fluid is collected by the patent periarterial spaces around the blood vessels of the WM, GM, and leptomeninges. B: The leptomeningeal and perforating cortical arteries supplying the brain GM and WM are surrounded by heavy amyloid deposits that destroy the vascular walls and block the perivascular spaces at the level of the cerebral cortex and leptomeninges. This obstruction results in WM congestion and stasis of interstitial fluid with simultaneous dilation of the WM perivascular spaces. The greater density and rigidity and lesser compliance of the GM matter leave this tissue substantially less affected than the WM.