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Published on: August 7, 2017
Differential and subtype-specific neuroimaging abnormalities in amnestic and nonamnestic mild cognitive impairment: A
Michael K Yeung1, Anson Kwok-Yun Chau2, Jason Yin-Chuen Chiu2
1Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China; University Research Facility in Behavioral and Systems Neuroscience, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
Abstract:
While mild cognitive impairment (MCI) has been classified into amnestic MCI (aMCI) and nonamnestic MCI (naMCI), the neuropathological bases of these two subtypes remain elusive. Here, we performed a systematic review and meta-analysis to determine the subtype specificity of neuroimaging abnormalities in MCI and to identify neural features that may differ between aMCI and naMCI. We synthesized 50 studies that used common neuroimaging modalities, including magnetic resonance imaging and positron emission tomography, to compare brain atrophy, white matter abnormalities, cortical thinning, cerebral hypometabolism, amyloid/tau deposition, or other features among aMCI, naMCI, and normal cognition. Compared with normal cognition, aMCI shows diverse neuroimaging abnormalities of large effect sizes. In contrast, naMCI exhibits restricted abnormalities of small effect sizes. Some features, including medial temporal lobe atrophy and white matter abnormalities, are shared by the two MCI subtypes. Overall, brain abnormalities are worse, if not similar, in aMCI than in naMCI. The only neuroimaging abnormality specific to aMCI is increased amyloid burden; no feature specific to naMCI was found. Taken together, our findings have elucidated the neuropathological changes that occur in aMCI and naMCI. Clarifying the neuroimaging profiles of aMCI and naMCI can improve the early identification, differentiation, and intervention of prodromal dementia.
Insights
Mild cognitive impairment (MCI) subtypes, amnestic MCI (aMCI) and nonamnestic MCI (naMCI), show distinct neuroimaging abnormalities. aMCI exhibits more widespread brain changes, while increased amyloid burden is specific to aMCI.
Area of Science:
- Neurology
- Neuroimaging
- Cognitive Science
Background:
- Mild cognitive impairment (MCI) is a transitional stage between normal aging and dementia.
- Subtyping MCI into amnestic (aMCI) and nonamnestic (naMCI) is crucial for understanding underlying neuropathology.
- The distinct neuroimaging profiles of aMCI and naMCI remain poorly understood.
Purpose of the Study:
- To systematically review and meta-analyze neuroimaging abnormalities in MCI subtypes.
- To determine subtype specificity of brain changes in aMCI versus naMCI.
- To identify neural features differentiating aMCI and naMCI.
Main Methods:
- Systematic review and meta-analysis of 50 studies.
- Inclusion of studies using magnetic resonance imaging (MRI) and positron emission tomography (PET).
- Comparison of brain atrophy, white matter abnormalities, hypometabolism, and amyloid/tau deposition across aMCI, naMCI, and normal cognition.
Main Results:
- aMCI demonstrates diverse neuroimaging abnormalities with large effect sizes compared to normal cognition.
- naMCI shows restricted abnormalities with small effect sizes.
- Medial temporal lobe atrophy and white matter abnormalities are common to both subtypes; increased amyloid burden is specific to aMCI.
Conclusions:
- Neuroimaging profiles of aMCI and naMCI are distinct, with aMCI generally showing more severe brain abnormalities.
- Increased amyloid burden is a specific neuroimaging marker for aMCI.
- Understanding these differences aids in early diagnosis and intervention for prodromal dementia.
