Vertex-wise shape analysis of subcortical structures in Alzheimerʼs disease

Background: Most MRI studies in Alzheimer’s disease (AD) have focused on cortical and hippocampal atrophy. This study, however, examines regional volumetric and shape abnormalities of subcortical and limbic structures in AD. Methods: Thirty-six patients with AD and 36 matched controls were included in the study. All subjects were right-handed, evaluated using standard clinical assessment scales and genotyped at ApoE locus. Structural T1- weighted images were acquired using 3 Tesla MRI. Vertex-wise shape analysis was performed, with age, gender and total brain volume used as covariates of no interest. Data on the volumes of the hippocampus, amygdala, caudate, putamen and thalamus were statistically analyzed. Results: The bilateral hippocampus, amygdala, caudate, putamen and thalamus of AD patients were significantly lower in volume than controls. With respect to ApoE4 carrier status, there were no within-group volumetric differences in either AD or controls. Vertex-wise shape analysis of AD patients revealed significant surface reductions at the bilateral hippocampus, amygdala, caudate and putamen. No shape-wise difference was observed between ApoE4 carrier and non-carrier subjects in either group. Correlation analysis revealed a significant negative correlation between the Hindi mental status examination score, and shape analysis of atrophy of the hippocampus, caudate and putamen. Conclusions: Significant volume reductions and shape differences were observed in subcortical and limbic structures in AD patients. The observed atrophy of neocortical and deep grey matter structures in AD patients indicates ongoing degenerative processes in the amygdala, caudate and putamen – similar to the hippocampus – which may contribute to cognitive and/or other clinical features in AD.