Three-dimensional surface mapping of the caudate nucleus in late-life depression

Abstract

Objective: To compare the volumes of the caudate nucleus, using traditional volumetry and a three-dimensional brain mapping technique, in a group of individuals with late-life depression and a group of age- and education-equated nondepressed comparison subjects.

Design: Cross-sectional.

Setting: University Medical Center.

Participants: Twenty-three nondemented subjects with late-life depression and 15 age- and education-equated elderly comparison subjects (depressed mean years of age: 70.5 +/- 5.7 SD, comparison subjects = 69.9 years +/- 6.4) with no history of psychiatric or neurologic disease.

Measurements: Structural magnetic resonance imaging. Three-dimensional (3-D) surface models were created from manually traced outlines of the caudate nucleus from spoiled gradient echo images. Models were geometrically averaged across subjects and statistical maps created to localize any regional volume differences between groups.

Results: Relative to comparison subjects, depressed subjects had significantly lower mean volumes for both the left (p = 0.029) and right (p = 0.052) caudate nucleus as well as total caudate volume (p = 0.032). Total volumes were 13.1% less in the depressed group (13.5% on the left and 12.6% on the right). 3-D maps further localized these reductions to the caudate head. Volume reductions were correlated with depression severity, as measured by the 17-item Hamilton Depression Rating Scale.

Conclusion: Late-life depression is associated with left and right caudate nucleus reduction especially in anterior portions. Among depressed subjects, greater caudate reduction was associated with more severe depression. These results are consistent with growing evidence that the anterior caudate nucleus, especially the head, may be structurally and functionally abnormal in affective disorders.

FIGURE 1. Maps of Caudate Reduction in Depressed Subjects, Adjusted for Age

Notes: The caudate is oriented so that it faces the reader and right and left are reversed. To better localize atrophic changes that might account for the overall 13% mean reduction in caudate volume, average surface maps were compared between the depressed and control groups. [A] Shows regions in red colors, that show evidence of reduction in radial size in the depressed group versus controls. The significance maps are assessing, at each point on the caudate surface, the t statistic for the group difference between patients and controls, for the radial distance between that point and a medial axis threading down the center of the caudate in each subject. As such, the t statistic has 37 df, i.e., one less than the total number of subjects in the study. The same distribution, with the same number of degrees of freedom, is used for the assessments of volume reduction. [B] Shows that the level of reduction reaches 10% in the most anterior caudate regions. [C] Shows a scatterplot, revealing the significant correlation between depression severity and caudate volumes, with the best fit line. The crossed lines on the left-hand side indicate the mean and 95% CI for both the Hamilton Depression Rating Scale-17 and caudate volumes of the comparison subjects (HDRS-17 mean: 1.80; CI: 0.90–1.8, Caudate mean: 6419, CI: 6746–6096).