Depression Relinquishes Secrets To Imaging

Various imaging data have associated abnormalities in brain structure and metabolism with late-life depression. The current study takes this analysis further by examining whether diffusion tensor imaging makes it possible to “see” changes associated with response to antidepressant drug therapy.

The study enrolled 48 elderly patients (age 60 and older) who were not demented nor delusional, but did suffer from major depression, as measured by a score of 18 or greater on the 24-item Hamilton Depression Rating Scale (HAM-D). All subjects received escitalopram 10 mg daily for 12 weeks. Thirty-nine completed the 12-week treatment and were re-evaluated. The 14 patients who achieved remission had lower HAM-D scores than the 23 who did not (mean scores: 4.7 versus 17.1, respectively). Diffusion tensor imaging showed the group that did not achieve remission also had lower fractional anisotropy in multiple frontal limbic brain areas, neostriatum, and subcortical white matter regions. (Anisotropy is a measure of orderliness regarding, in this case, the diffusion of water in brain structures.) On the other hand, the nonremitters had two areas of higher fractional anisotropy – the left precentral gyrus and left inferior parietal white matter.

The results confirm the presence of white matter abnormalities in late-life depression, using structural neuroimaging. They also suggest the feasibility of monitoring patients for their response to antidepressant drug therapy. Whether it will be possible to use diffusion tensor imaging to identify responders from nonresponders early in the course of drug treatment will require additional study. It might even be possible to combine structural and functional imaging techniques to identify patients with microanatomical abnormalities that are predisposing to nonremission of geriatric depression from incidental abnormalities before beginning a particular type of drug therapy.

Message posted by: Keith Markey