Measurement of precuneal and hippocampal volumes using magnetic resonance volumetry in Alzheimer's disease

Abstract

Background and purpose: Alzheimer's disease (AD) is associated with structural alterations in the medial temporal lobe (MTL) and functional alterations in the posterior cortical region, especially in the early stages. However, it is unclear what mechanisms underlie these regional discrepancies or whether the posterior cortical hypometabolism reflects disconnection from the MTL lesion or is the result of local pathology. The precuneus, an area of the posteromedial cortex that is involved in the early stages of AD, has recently received a great deal of attention in functional neuroimaging studies. To assess the relationship between the precuneus and hippocampus in AD, we investigated the volumes of these two areas using a magnetic resonance volumetric method.

Methods: Twenty-three subjects with AD and 14 healthy age-matched controls underwent T1-weighted three-dimensional volumetric brain magnetic resonance imaging. Volumetric measurements were performed in the precuneus and hippocampus.

Results: Compared to controls, AD patients exhibited a significant reduction in total precuneal volume, which was more prominent on the right side, and significant bilateral reductions in hippocampal volume. No correlation was found between the total volumes of the precuneus and hippocampus in the AD group.

Conclusions: These results suggest that volumetric measurements of both the precuneus and hippocampus are useful radiological indices for the diagnosis of AD. Furthermore, the lack of correlation is attributable to local pathology rather than being a secondary consequence of MTL pathology.

Keywords: Alzheimer's disease; hippocampus; magnetic resonance imaging; precuneus; volumetry.

Fig. 1

Overall block diagram of image processing step. MR: magnetic resonance, VOIs: volumes of interest, FCM: fuzzy c-means.

Fig. 2

Ten reference points for Talairach coordinates. CA: anterior commissure, CP: posterior commissure, AP: most-anterior point, PP: most-posterior point, SP: most-superior point, IP: most-inferior point, RP: rightmost point, LP: leftmost point, MH: high point to define the midline, ML: low point to define the midline.

Fig. 3

Example of manual tracing of the total intracranial volume in a sagittal section (white line).

Fig. 4

Example of regions of interest illustrating the boundaries of the left precuneus (A) in the sagittal plane, and the right hippocampus head (B), body (C), and tail (D) in the coronal planes.