This BRAIN-ICU-2 study \[Bringing to light the Risk factors And Incidence of Neuropsychological dysfunction (dementia) in ICU Survivors, 2nd Study\] is in direct response to PAR-17-038 and will determine ICU patients' main paths to decline, maintenance, or recovery of brain function. We will answer gaps in knowledge about long-term outcome of post-ICU brain disease by following the remaining ICU survivors from the original BRAIN-ICU-1 study with complete cognitive testing for the first time ever to 12 years (AIM 1). We will consent and enroll 567 new ICU patients at Vanderbilt and Rush Universities (i.e., BRAIN-ICU-2 cohort) and determine how detailed neuroimaging and cerebrospinal fluid samples can help reveal locations and mechanisms of injury beyond what we learned from the clinical information collected in our original study (AIM 2). Importantly, we are mirroring the existing world-renowned Rush Alzheimer's Disease Research Center brain bank program so that all patients enrolled in Aims 1 and 2 will able to donate their brains to science for the first-ever in-depth pathological study of those who do and do not get post-ICU dementia to define this disease formally (AIM 3)