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Medial temporal atrophy on MRI in normal aging and very mild Alzheimer's disease
C R Jack1, R C Petersen, Y C Xu
1Department of Diagnostic Radiology, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Abstract:
Magnetic resonance imaging (MRI)-based volumetric measurements of medial temporal lobe (MTL) structures can discriminate between normal elderly control subjects and patients with Alzheimer's disease (AD) of moderate to advanced severity. In terms of clinical utility, however, a more important issue concerns the ability of the technique to differentiate between normal elderly control subjects and AD patients with the very mildest form of the disease. We performed MRI-based volumetric measurements of the hippocampus, parahippocampal gyrus, and amygdala in 126 cognitively normal elderly control subjects and 94 patients with probable AD. The diagnosis of AD was made according to NINDS/ADRDA criteria, and disease severity was categorized by Clinical Dementia Rating (CDR) scores. Patients with CDR 0.5 were classified as very mild, CDR 1 as mild, and CDR 2 as moderate disease severity. Volumes of each structure declined with increasing age in control subjects and did so in parallel for men and women. The volume of each measured MTL structure also declined with age in patients with AD. The volume of each MTL structure was significantly smaller in AD patients than control subjects (p < 0.001). Of the several MTL measures, the total hippocampal volumetric measurements were best at discriminating control subjects from AD patients. The mean hippocampal volumes for AD patients relative to control subjects by severity of disease were as follows: very mild AD (CDR 0.5) -1.75 SD below the control mean, mild AD (CDR 1) -1.99 SD, and moderate AD (CDR 2) -2.22 SD. Age- and gender-adjusted, normalized MRI-based hippocampal volumetric measurements provide a sensitive marker of the MTL neuroanatomic degeneration in AD early in the disease process.
Insights
Magnetic resonance imaging (MRI) can detect early Alzheimer's disease (AD) by measuring medial temporal lobe (MTL) structure volumes. Hippocampal volume reduction is a sensitive marker for neurodegeneration, even in very mild AD cases.
Area of Science:
- Neuroimaging
- Neurology
- Gerontology
Background:
- Medial temporal lobe (MTL) structure volumetry via MRI can distinguish moderate to advanced Alzheimer's disease (AD) from normal aging.
- A key clinical challenge is differentiating early-stage AD from normal cognition.
Purpose of the Study:
- To assess the utility of MRI-based volumetric measurements of MTL structures (hippocampus, parahippocampal gyrus, amygdala) in discriminating very mild AD from normal elderly controls.
- To evaluate the relationship between MTL structure volumes, age, and disease severity in AD.
Main Methods:
- Volumetric MRI scans were performed on 126 cognitively normal elderly subjects and 94 probable AD patients.
- AD diagnosis followed NINDS/ADRDA criteria; severity was staged using Clinical Dementia Rating (CDR) scores (0.5=very mild, 1=mild, 2=moderate).
- Age- and gender-adjusted hippocampal volumes were analyzed for their discriminative ability.
Main Results:
- All measured MTL structures showed significant volume reduction in AD patients compared to controls (p < 0.001).
- Hippocampal volume was the most effective measure for discriminating between AD patients and controls.
- Mean hippocampal volumes in AD patients were -1.75, -1.99, and -2.22 SD below the control mean for very mild, mild, and moderate AD, respectively.
Conclusions:
- Normalized MRI-based hippocampal volumetry is a sensitive biomarker for detecting MTL neurodegeneration in the early stages of Alzheimer's disease.
- This technique aids in the early diagnosis of AD, facilitating timely intervention and management.