Gray and white matter brain volumes in older adults with bipolar disorder

Abstract

Objectives: Structural magnetic resonance imaging (MRI) studies have been inconsistent in demonstrating volumetric differences in subjects with bipolar disorder. Most studies have not found difference in total gray or white matter in bipolar patients compared with controls, but there have been several studies suggesting that regional abnormalities are present. These have predominately been located in the frontal and temporal lobes. Since age has been inversely correlated with total gray matter in patients, analyses of gray matter changes in older adults or in studies that have included older subjects have been difficult. This study assessed the presence of gray matter volume, and the potential for regional volumetric differences in older adults with bipolar disorder.

Methods: Fifty-six older adults with DSM-IV bipolar disorder (mean age 60.5) and 43 non-psychiatrically ill controls (mean age 58.1) had structured interviews and MRI scanning on a 1.5T GE Scanner. Image parcellation divided the cerebrum into 16 units. Volumetric differences were examined using the multivariate linear regression models with alpha = 0.05.

Results: Relative to controls, the older adults with bipolar disorder had significantly smaller gray matter volumes bilaterally in the inferior frontal areas. White matter volume was also reduced in these same areas but did not reach statistical significance when controlled for gender and age. No significant difference was noted in total gray or white matter volumes.

Conclusions: Older adults with bipolar disorder showed gray matter volumetric deficits in inferior frontal lobe regions which include structures identified as contributing to the anterior limbic network.

Figure 1

Placement of dividing planes. In this mid-sagittal view, AC–PC and corpus callosum (anterior, posterior, and middle) planes are visible.

Figure 2

Numbered diagram of the 16 parcellation regions. Regions 1–4 are anterior to corpus callosum. Regions 13–16 are posterior to corpus callosum. Odd-numbered regions are inferior to AC–PC plane, while even-numbered are above. Plane separating regions 5–8 from 9–12 is midway between anterior and posterior of corpus callosum.