Analysis of MRI-based cortical surface structure complexity in dementia by sample entropy

Dementia is a most common neurodegenerative disorder. Previous researches have attempted to relate the impairment of cognition to volumes or thickness changes of the cortical regions, with relatively few studies investigating other features such as cortical surface anatomy. In the present study, we report for the first time to use sample entropy (SampEn) to assess the complexity of cortical surface structure in early stage of dementia compared to healthy controls. Whole brain structural T1-weighted MRI scans were collected from 192 subjects including patients with very mild and mild dementia (age = 77 ± 7, male/female = 41/55, CDR = 0.5 or 1, n = 96), and healthy subjects (aged = 76 ± 9, male/female= 25/70, CDR = 0, n = 96). SampEn was applied to each transection and averaged. Comparisons were made between control and dementia for the whole brain as well as for each sub-section of all layers. Results show an overall larger SampEn in demented group compared with non-demented group(p <; 0.05) which indicate an increase of structural irregularity of cortical surface in dementia. Our findings offer a novel approach for studying cortical atrophy patterns and can potentially be used to develop novel biomarkers of dementia.