CSF tau correlates with CJD disease severity and cognitive decline

Background Creutzfeldt–Jakob disease (CJD) is the most common prion disease in humans. The clinical diagnosis of CJD is supported by a combination of electroencephalogram, MRI, and the presence in the CSF of biomarkers. CSF tau is a marker for neuronal damage and tangle pathology, and is correlated with cognitive status in Alzheimer's disease (AD). Objectives The aim of this study was to test whether tau levels in the CSF also correlate with the degree of the neurological deficit and cognitive decline in patients with CJD as reflected by various clinical scales that assess disease severity and cognitive performance. Methods Consecutive patients with familial CJD (fCJD) were examined by a neurologist who performed several tests including minimental status examination (MMSE), frontal assessment battery (FAB), NIH stroke scale (NIHSS), CJD neurological scale (CJD‐NS), and the expanded disability status scale (EDSS). CSF tau was tested as part of the workout, and the correlation was tested using Pearson correlation. Results Fifty‐two patients with fCJD were recruited to the study (35 males, mean age 59.4 ± 5.7, range 48–75 years). A significant negative correlation was found between CSF tau levels and the cognitive performance of the patients as reflected by their MMSE and FAB scores. In addition, a significant positive correlation was found between tau levels and the clinical disease severity scales of CJD‐NS, NIHSS, and EDSS. Conclusion The correlation between tau levels and the disease severity and degree of cognitive decline in patients with fCJD suggests that tau can be a biomarker reflecting the extent of neuronal damage.