Fig. 1.

Widespread oedema is clearly evident in supragranular layers of gray matter (A) by Hematoxylin and Eosin (HE) staining. Small vessel disease (SVD) is identified by perivascular space dilatation, features of arteriolosclerosis (B), and myelin loss (C) observed respectively by HE and Luxol Fast Blue stainings. In cases with a low amount of viral RNA perivascular inflammatory infiltrates appear as the most prominent inflammatory feature (D; HE staining); while in cases with dementia and higher amount of viral RNA there are more prominent microglial nodule as shown by both, HE (E) and CD68 antibody (F). In COVID-19 cases affected by Alzheimer’s Disease, 4G8 antibody detects amyloid plaques (G) and, possibly, cerebral amyloid angiopathy (H). In the same cases, AT8 immunoreactivity shows neuritic plaques, tangles and threads in frontal cortex (I), hippocampus (J) and occipital cortex (K). Three COVID-19 cases with dementia are shown in panels A-C and E-K, while panel D shows a COVID-19 case without dementia carrying al low viral RNA load. Images include frontal lobes (A-I), hippocampus (J) and occipital lobe (K). Scale bar: 256 µm (A,G); 340 µm (B,H,I,J,K); 807 µm (C); 122 µm (D,F); 73 µm (E). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)