The presence of capillary CAA does not appear to be associated with cognitive decline,89 and although both ApoE ε2 and ApoE ε4 are associated with CAA, it is ApoE ε4 that is associated with more severe CAA on neuropathological examination (as defined by Vonsattel grading).111 112 Additionally, ApoE ε4 has been shown to be associated with cSS in a memory clinic population.41 Further data on the cognitive impact of ApoE ε2 in CAA, in particular whether it has an effect on cognition beyond the direct damage caused by macrohaemorrhage, are needed. This evidence concerns the gene APOE and Mental deterioration.