Structural Brain Biomarkers for Identifying Progressive Amnestic Mild Cognitive Impairment

Objective. To identify the structural features of the brain in patients with amnestic mild cognitive impairment (aMCI) compared to healthy individuals, as well as to detect structural markers of progression to dementia in aMCI subgroups with different clinical outcomes. Materials and Methods. 41 patients with aMCI (mean age 71.5{+/-}9.5 years, 33 females) who underwent clinical assessment during 1 year follow-up, and 38 healthy controls (mean age 63.7{+/-}11.7 years, 28 females) were included. MRI scans were acquired, and the cortical thickness in both hemispheres, as well as the volumes of subcortical structures and hippocampal subfields, were analyzed. Results. Patients with aMCI as a whole, as well as aMCI subgroups with different clinical outcomes, showed significantly smaller bilateral hippocampal volumes and volumes of several hippocampal subfields than healthy controls. In addition, patients who were subsequently diagnosed with Alzheimer's disease dementia exhibited lower cortical gray matter thickness and smaller bilateral amygdala volumes than the healthy controls. Several subcortical structures and hippocampal subregions remained preserved in patients with aMCI, including those with unfavorable clinical outcomes. Conclusion. The study revealed structural brain abnormalities in aMCI, characterized by reduced hippocampal and hippocampal subfield volumes, as well as amygdala volume reduction, while other subcortical structures were relatively preserved. Furthermore, reduced cortical gray matter thickness may serve as a potential prognostic marker for conversion to dementia in patients with aMCI.