ENO2 and Alzheimer disease: Elevated levels of serum NSE were consistently linked with cerebral ischemia, encephalitis, Parkinson's disease, etc. Previous findings in AD were mixed: no changes of NSE in serum or CSF (van den Doel et al., 1988; Parnetti et al., 1995) or increased NSE in CSF (Palumbo et al., 2008; Schmidt et al., 2014).