Contributions from brain imaging to the elucidation of pathophysiology of bipolar disorder

Over the past two decades, brain-imaging studies have examined the mechanisms possibly involved in the pathophysiology of bipolar and unipolar mood disorders. The available findings suggest subtle anatomical changes in sub-regions of the prefrontal cortex, medial temporal lobe and cerebellum, and functional abnormalities in brain circuits inter-connecting these same brain regions and the striatum in patients suffering from bipolar disorder. 1H magnetic resonance spectroscopy (MRS) studies reported decreased N-acetyl aspartate (NAA) levels in the dorsolateral prefrontal cortex, and 31P-MRS studies found abnormalities in membrane phospholipids in frontal and temporal regions in bipolar individuals. Few studies have utilized in-vivo receptor imaging to study bipolar patients. Even though preliminary findings from cross-sectional studies indicate anatomical, neurochemical, and functional brain abnormalities in bipolar patients in key regions involved in mood regulation, the relationship of such abnormalities with illness phase and their clinical relevance needs further investigation. The potential for utilization of brain-imaging tools to elucidate the pathophysiology of bipolar disorder is still largely unrealized, and it is anticipated that important new developments in this area will come about over the next years and beyond.