MEDIAL TEMPORAL ATROPHY ON MRI IN NORMAL AGING AND VERY MILD ALZHEIMERS-DISEASE

Magnetic resonance imaging (MRI)-based volumetric measurements of medi al temporal lobe (MTL) structures can discriminate between normal elde rly control subjects and patients with Alzheimer's disease (AD) of mod erate to advanced severity. In terms of clinical utility, however, a m ore important issue concerns the ability of the technique to different iate between normal elderly control subjects and AD patients with the very mildest form of the disease. We performed MRI-based volumetric me asurements of the hippocampus, parahippocampal gyrus, and amygdala in 126 cognitively normal elderly control subjects and 94 patients with p robable AD. The diagnosis of BD was made according to NINDS/ADRDA crit eria, 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 st ructure 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 st ructure was significantly smaller in AD patients than control subjects (p < 0.001). Of the several MTL measures, the total hippocampal volum etric measurements were best at discriminating control subjects from A D patients. The mean hippocampal volumes for AD patients relative to c ontrol 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, an d moderate AD (CDR 2) -2.22 SD, Age- and gender-adjusted, normalized M RI-based hippocampal volumetric measurements provide a sensitive marke r of the MTL neuroanatomic degeneration in AD early in the disease pro cess.