Objective-To test the hypothesis that magnetic resonance imaging (MRI)-based measurements of hippocampal volume were related to the risk of future conversion to Alzheimer's disease (AD) in elderly patients with a mild cognitive impairment (MCI) Background-Persons who develop AD pass through a transitional state which can be characterized as a MCI. However, in some patients MCI is a more benign condition which may not progress to AD or may do so slowly.

Magnetic resonance imaging(MRI) based volumetric measurements of medial temporal lobe (MTL) structures can discriminate between normal elderly controls 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 controls and AD patients with the very mildest form of the disease. We performed MRI-based volume measurements of the hippocampus, parahippocampal gyrus, and amygdala in 126 cognitively normal elderly controls 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 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<.001). Of the several MTL measures, the total hippocampal volume measurements were best at discriminating controls from AD cases. The mean hippocampal volumes for AD patients relative to controls 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 volume measurements provide a sensitive marker of the MTL neuroanatomic degeneration in AD early in the disease process. KeywordsAlzheimer's Disease; Dementia; MRI; Quantitative MRI; Hippocampus Alzheimer's disease(AD) is the most common cause of dementia in individuals over 60 years of age(1-3). A well accepted biological concomitant of AD is cerebral atrophy(4). The rationale for quantitative magnetic resonance imaging (MRI) of medial temporal lobe (MTL) atrophy in the diagnosis of AD is: 1) A memory impairment is usually the earliest and most severe clinical manifestation of AD; 2) Medial temporal lobe (MTL) limbic structures are central to the integrity of declarative memory function (5); 3) MTL limbic structures are involved earliest and most extensively in the pathology of AD(6,7); and 4) several principal MTL limbic structures are amenable to accurate volumetric quantitation by MRI-the hippocampal 3) Relatively small numbers of subjects were included in individual studies. 4) Rigorous definitions of the severity of AD often were not employed. Most previous studies have included primarily subjects with AD of moderate severity. Consequently, the differences between the AD patients and control subjects with regard to MTL atrophy have been dramatic. The most important test of the utility of the technique would be in patients with very mild AD in whom the diagnostic decision making process is difficult.We report a large series of carefully evaluated and lon...

Background-The cognitive continuum in the elderly population can be conceptually divided into those who are functioning normally (controls), those with a mild cognitive impairment (MCI), and those with probable AD.

Despite the theoretical rationale for the superiority of entorhinal measurements in early AD, the authors found MRI measurements of the hippocampus and entorhinal cortex were approximately equivalent at intergroup discrimination. Measurements of the hippocampus may be preferable because MRI depiction of the boundaries of the entorhinal cortex can be obscured by anatomic ambiguity, image artifact, or both.

Hippocampal ADC was significantly different between control subjects and MCI patients, many of whom likely have preclinical Alzheimer disease. Elevation in hippocampal ADC may reflect early ultrastructural changes in the progression of Alzheimer disease.