Rate of medial temporal lobe atrophy in typical aging and Alzheimer's disease

Abstract

Objectives: To determine the annual rates of volumetric change of the hippocampus and temporal horn in cognitively normal elderly control subjects and individually matched patients with AD, and to test the hypothesis that these rates were different.

Background: Cross-sectional studies consistently reveal cerebral atrophy in elderly nondemented subjects compared with healthy young adults, and greater atrophy in patients with AD relative to elderly control subjects. However, rates of atrophy are estimated most accurately by performing serial measurements in the same individuals.

Methods: MRI-based volumetric measurements of the hippocampi and temporal horns were performed in 24 cognitively normal subjects aged 70 to 89 years who were individually matched with respect to gender and age with 24 patients with AD. Each subject underwent an MRI protocol twice, separated by 12 months or more.

Results: The mean annual rate of hippocampal volume loss among control subjects was -1.55+/-1.38% and the temporal horns increased in volume by 6.15+/-7.69% per year. These rates were significantly greater among AD patients: hippocampus, -3.98+/-1.92% per year, p < 0.001; temporal horn, 14.16+/-8.47% per year, p = 0.002.

Conclusion: A statistically significant yearly decline in hippocampal volume and an increase in temporal horn volume was identified in elderly control subjects who represent typical aging individuals. These rates were approximately 2.5 times greater in patients with AD than in individually age- and gender-matched control subjects.

Figure 1. Structure Boundaries

Boundaries of the hippocampus indicated on the patient's left and the temporal horn on the right

Figure 2. Annual Percent Volumetric Change

Box plots illustrating the annual percent volumetric change of the hippocampus and temporal horn separately for cases and controls. For each group the horizontal line in the box represents the median value, the box represents the 25th and 75th percentiles, the circle represents the mean, and the vertical line represents the range of values in each group. The 0 in the temporal horn column of controls indicates the value of a lone outlier.