Genomic Expression and Neuropsychiatric Evaluation - David A. Mrazek

Neuroimaging and Bipolar Illness

Until very recently, neuroimaging has played a relatively limited role in the psychiatric evaluation of children. There are now new developments in functional imaging which hold great promise for psychiatry. New strategies for demonstrating abnormalities in bipolar patients using imaging are being developed at Mayo Clinic.

One theory about the etiology of bipolar disorder is based on the observation that lithium is an effective mood stabilizer for many patients. Defects in signaling may result in clinical symptoms. A second theory states that bipolar disorder is aggravated by abnormal connections between various brain regions. Such abnormal connections may result in impaired feedback loops, which are associated with manic and depressed states.

Two relatively new neuroradiological techniques may be especially suited for the diagnosis of bipolar disease and other psychotic illnesses. Magnetic resonance spectroscopic imaging (MRSI) allows for the direct study of brain function. Diffusion tensor imaging (DTI) allows for mapping of the connections within the living brain. As a result, white matter connections between various brain regions can be studied. In collaboration with Dr. John D. Port in the Department of Radiology, psychiatrists at Mayo Clinic are studying these new applications.

The supplied images are an example from one study subject. The reference image (A, upper left) shows a T1-weighted reference slice overlaid with the location of the PRESS voxel and the phase encode grid. Quantitative creatine, myo-inositol and N-acetyl-aspartate levels (A, upper right, lower left, and lower right images, respectively) as determined by LCModel are also shown. In these metabolite maps, values are linearly scaled such that yellow voxels have the maximum concentration of a given metabolite, with darker shades representing lesser concentrations. Green voxels have standard deviations greater than 19% and are considered "unreliable" by LCModel criteria.

Figure B shows the spectrum from the right thalamus, corresponding to the red arrow in Figure A; note the quantitative values for each metabolite.