Volumes of lateral temporal and parietal structures distinguish between healthy aging, mild cognitive impairment, and Alzheimer's disease.

Distinguishing amnestic mild cognitive impairment (MCI) from Alzheimer's disease (AD) and healthy aging depends mainly on clinical evaluation, and, ultimately, on investigator's judgment. Clinical evaluation in vivo is based primarily on cognitive assessments. The present study explores the potential of volumetric magnetic resonance imaging of parietal and lateral temporal brain structures to support the diagnosis of AD and to distinguish AD patients from patients with MCI and healthy control subjects (HCS). 52 age-matched HCS, 18 patients with MCI, and 59 patients with probable late onset AD were investigated. Using computational, neuromorphometric procedures gray matter (GM) was automatically parcellated into 28 local regions of interest, the volumes of which were computed. The left hippocampus (sensitivity/specificity: 80.8-90.4%/55.6-86.4%) and the right hippocampus (73.1-90.4%/66.7-84.7%) provided highest diagnostic accuracy in separating all three diagnostic groups. Promising diagnostic values for distinguishing MCI from HCS were found for the left superior parietal gyrus (61.5%/55.6%) and left supramarginal gyrus (65.4%/66.7%), and for distinguishing subjects with MCI from AD patients for the right middle temporal gyrus (77.8%/79.7%), left inferior temporal gyrus (83.3%/72.9%), and right superior temporal gyrus (77.8%/71.2%). The left superior temporal pole (92.3%/84.7%), left parahippocampal gyrus (86.5%/81.4%), left Heschl's gyrus (86.5%/79.7%), and the right superior temporal pole (82.7%/78.0%) revealed most promising diagnostic values for distinguishing AD patients from HCS. Data revealed that lateral temporal and parietal GM volumes distinguish between HCS, MCI, and AD as accurate as hippocampal volumes do; hence, these volumes can be used in the diagnostic procedure. Results also suggest that cognitive functions associated with these brain regions, e.g., language and visuospatial abilities, may be tested more extensively to obtain additional information that might enhance the diagnostic accuracy further.