APOE and Hydrocephalus: Of these, 24 were excluded due to incidental findings on MRI (n = 5 small vessel disease or lacunar infarctions, n = 2 meningiomas, n = 1 mild hydrocephalus, n = 1 demyelination), MR artifacts (n = 2), incomplete 31P-MRS studies (n = 3) or out-of-range metabolite ratios (n = 3), and incomplete APOE4 data (n = 7).