| Abstrakt: |
Background: Hippocampal volume (HCvol) is an important biomarker in the study of neurodegeneration (1‐3). Given its high variability (4) HCvol is commonly normalized using the intracranial volume (HCvol/ICV) (5). The Hippocampal‐to‐ventricle ratio (HVR) considers instead the nearby expanding ventricular space and has shown stronger negative association with age and positive association with delayed memory compared to HCvol in healthy aging (6). Method: Using a Convolutional Neural Network (7) we extracted the volumes from the hippocampus and the surrounding temporal horn of the lateral ventricles to obtain the HCvol, HCvol/ICV and HVR on the baseline T1w MRI scans from the ADNI dataset (CN = 502, MCI = 814, AD = 323). We converted these measurements to Z‐scores using the mean and standard deviation of the CN cohort to facilitate comparisons. We used Pearson's correlation coefficient to compare the relationships between each of the three Hippocampal measures with age, ADAS13, and the Immediate, Learning, Forgetting and Forgetting‐percentage metrics of the Rey's Auditory Verbal Learning Test (RAVLT). Finally, we compared the correlations of HCvol/ICV and HVR with a bias‐corrected‐and‐accelerated bootstrap (BCa; 10,000 resamples) (8). Result: The correlations of HCvol and HCvol/ICV were similar for age (‐.41 [‐.32, ‐.48] vs ‐.38 [‐.3, ‐.45]), ADAS13 (‐.28 [‐.19, ‐.45] vs ‐.26 [‐.17, ‐.45]) and RAVLT subtests (absolute values:.2 [0,.4] vs.2 [.01,.41]). HVR showed significantly stronger negative correlations with age compared to HCvol/ICV (Fig. 1; CN: BCa =.144 [.102‐.187]; MCI: BCa =.128 [.096‐.160]; AD: BCa =.068 [.012‐.122]). While the negative correlations between HVR and ADAS13 scores were higher than HCvol, the comparison was not statistically significant (Fig. 2). Figure 3 shows the relationships between HC measures and RAVLT subtests: HVR had stronger correlations than HCvol for CN and AD on the Immediate subtest, while HCvol's relationship with Forgetting score was higher for MCI. None of these were statistically significant. Conclusion: Considering ventricular expansion and hippocampal shrinkage in the HVR better explains the variance related to age and cognition than using hippocampal volume by itself in healthy controls and patients with mild cognitive impairment and dementia. [ABSTRACT FROM AUTHOR] |
