Based on results showing increased levels of PKR in AD brains, we have evaluated the CSF levels of total and phosphorylated PKR in AD patients (n = 45) in mild cognitive impairment (MCI) due to AD with abnormal CSF biomarkers (n = 11) and in neurological controls (n = 35) with normal CSF biomarkers [76]. Here, EIF2AK2 is linked to Alzheimer disease.