Callosal Angle and Evans Index predict beta amyloid and tau protein in patients with dementia.

INTRODUCTION: Aß and tau protein have been widely investigated for the diagnosis of dementia entities, most commonly Alzheimer's disease (AD). However, their measurement is an interventional, time-consuming procedure, while it requires specialized personnel, unlike the evaluation of radiological markers, such as Evans index (EI) and Callosal angle (CA). This study aims to investigate the correlation between EI, CA, Aß and total tau in order to outline a basis of diagnostic evaluation for the patient's CSF biomarker profile. METHODS: Sixty-two (62) patients who presented with dementia symptoms participated in this study. Aß and total tau levels in their CSF as well as CA and EI values from their MRIs were measured. Multiple regression was employed to predict Aß and total tau values from EI and CA. From the Durbin-Watson analysis (d1=2.057, d2=1.881) we can assume that there is no first order linear auto-correlation in our multiple linear regression data. RESULTS: The variables statistically significantly predicted both Aß and total tau (F1=8.720, R1=0.484, p1=0.001 and F2=4.110, R2=0.355, p2=0.022). Out of all the variables, it was shown that CA, EI (p<0.05) and CA (p<0.05) added statistically significantly to the prediction of Aß and total tau. CONCLUSION: Collectively, these results support a significant correlation between EI and Aß and CA, Aß and total tau. This highlights the potential role of radiological markers as rough estimates of biomarker levels in everyday clinical practice, assisting to a robust and inexpensive diagnosis.

The correlation of Evans index with CSF protein levels and ventriculomegaly.

OBJECTIVE: The role of ventriculomegaly and its interplay between various dementia entities and their pathogenesis, as well as its correlation to the levels of CSF protein markers, remains to be elucidated. Evans index (EI) is a well-established radiological marker in the diagnosis of idiopathic Normal Pressure Hydrocephalus (iNPH), assessing ventricular enlargement. However, there are no previous studies investigating the correlation between EI, age, beta amyloid (Aß), tau and phosphorylated-tau (p-tau) proteins in the CSF. The aim of this study was to examine the correlation of the above CSF proteins, EI and age in patients with dementia. METHODS: Sixty two (62) patients, with dementia and levels of Aß, Tau and p-Tau in their CSF as well as age and the EI participated in this study. Multiple regression analysis was performed to investigate possible correlations between the aforementioned factors. A multiple regression was employed to predict Aß values from age, tau and p-tau values in the CSF. The Durbin-Watson d was 1.942 so we can assume that there is no first order linear auto-correlation in our multiple linear regression data. RESULTS: The variables statistically significantly predicted Aß, F-value=4.429, P=0.011, R2=0.483. Specifically, out of all the variables, it was shown that only EI and age added statistically significantly to the prediction, P<.05. Specifically, these results are interpreted as: for every 0.01 unit increase in EI, it was predicted a -38.698 decrease in the Αß value and for every 1 year increase in age, it was predicted a -17 decrease in the Αß value. CONCLUSION: There seems to be a significant correlation between EI value, age and Aß reduction in the CSF. No correlation was found between EI and tau and p-tau proteins in the CSF. This may indicate that Aß levels in the CSF are affected significantly by ventriculomegaly and not as much by pathophysiological pathways characteristic for each dementia entity. On the other hand, tau and p-tau proteins could possibly play a crucial role in the differential diagnosis of iNPH and other dementia entities, as these proteins cannot be predicted by ventricular enlargement.