Significant global structural alterations have been identified in mild cognitive impairment (MCI) and Alzheimer disease (AD) using a multivariate analysis of covariance (MANCOVA) model, according to a study published in the May issue of Academic Radiology.
Discerning MCI and AD from healthy aging is a persistent problem, especially as the prevalence of Alzheimer’s continues to increase. “The accumulation of the disease pathology during predementia may result in macroscopic structural alterations in the brain, which allows characterization of the transition events of the disease and differentiating it from healthy aging,” wrote lead author Weiqi Liao, MMed, of the Chinese Academy of Sciences in the Guangdong Province of China, and colleagues.
The researchers sought to investigate the cerebral structural alterations of MCI and AD on the basis of cerebral surface area, curvature index, cortical thickness and subjacent white matter volume collectively by MANCOVA. They also reassessed individual morphologic parameter use by analysis of covariance (ANCOVA) in the disease characterization.
Using T1-weighted images from the Alzheimer Disease Neuroimaging Initiative database, they selected 116 subjects and divided them into three groups: healthy aging, MCI and AD. ANCOVA and MANCOVA were performed in order to investigate intergroup morphologic alterations. These alterations were indexed by surface area, curvature index, cortical thickness and subjacent white matter volume in 34 parcellated gyri regions of interest for both cerebral hemispheres.
After MANCOVA was performed, the study’s results indicated that global structural alterations were evident in the MCI and AD groups in relation to the healthy participants. ANCOVA revealed that cortical thickness decreased in entorhinal, temporal and cingulate cortices in the AD group but not that of the MCI.
On average, cortical thickness and white matter volume of the MCI group decreased respectively by 4.2 percent and 2.8 percent in comparison with the healthy elders. These indices decreased by 8.7 percent and 7.7 percent in comparison with AD patients. Cortical thickness was positively correlated with cognitive performance of patients.
Moreover, features of the temporal lobe showed atrophy of the white matter during disease dynamics. Significant intercorrelations were observed in the morphologic indices with univariate analysis for the regions of interest.
“The pooled data with Pearson correlation analysis in this study confirmed the significant intercorrelation among the four measures at both intragroup and intergroup levels,” wrote Liao and colleagues. “Full model of MANCOVA in the present work revealed global rather than regional cerebral alteration in MCI and AD. Given the progressive nature of the disease, the model with improved sensitivity may be more beneficial in screening the diseased brain at the preclinical stage of AD.”