Progression of Corpus Callosum Atrophy in Early Stage of Alzheimer's Disease. MRI Based Study

Rationale and Objectives: Magnetic resonance imaging (MRI) studies reveal that atrophy of the corpus callosum (CC) is involved in early Alzheimer's disease (AD). The aim of this study was to investigate when and how callosal changes occur in the early course of AD. Materials and Methods: The Open Access Series of Imaging Studies data sets were used in this study to investigate callosal change. High-resolution structural MRI was performed in 196 older patients. Subjects were characterized using the Clinical Dementia Rating (CDR); 98 healthy controls were not demented (CDR 0), and 98 patients had clinical diagnosis of AD in the very mild dementia stage (CDR 0.5; n = 70) and the mild dementia stage (CDR 1; n = 28). A semiautomatic segmentation method was used to extract the CC in the midsagittal plane. The total and regional areas of the CC were measured. Results: The results indicated that callosal atrophy occurred in when subjects' CDRs were 0.5. The area of the genu and rostral body of the CC in the healthy controls (CDR 0) was significantly different from that of the subjects with very mild dementia (CDR 0.5) (P < .05). A significant difference could also be found in the area of the rostral body and midbody of the CC between subjects with very mild dementia (CDR 0.5) and those with mild dementia (CDR 1) (P < .05). Conclusions: Callosal atrophy can be detected in subjects with CDRs of 0.5. The change in the CC in the early stage of AD indicates an anterior-to-posterior atrophic process as the degree of dementia assessed by the CDR (from 0 to 0.5 to 1) increases.