MAPT and cardiac arrest: Reducing the number of microglial cells and inhibiting exosome synthesis reduces the spread of tau proteins (Asai et al., 2015); thus, serum levels of tau protein are useful to support findings of acute neuronal damage, including acute ischemic stroke, traumatic brain injury, intracranial hemorrhage, epilepsy, and cardiac arrest (Bitsch et al., 2002; Palmio et al., 2009; Hu et al., 2012; Randall et al., 2013; Mattsson et al., 2017; Tang et al., 2019; Nakada et al., 2020).