Neuroimaging in bipolar disorder

Objective: The authors reviewed neuroimaging studies of bipolar disorder in order to evaluate how this literature contributes to the current understan ding of the neurophysiology of the illness. Method: Papers were reviewed as identified, using the NIMH PubMed literatur e search systems that reported results of neuroimaging studies involving a minimum of five bipolar disorder patients compared with healthy comparison subjects. Results: Structural neuroimaging studies report mixed results for lateral a nd third ventriculomegaly. Recent studies suggest subcortical structural ab normalities in the striatum and amygdala, as well as the prefrontal cortex. Proton spectroscopic studies suggest that abnormalities in choline metabol ism exist in bipolar disorder, particularly in the basal ganglia. Additiona lly, phosphorous MRS suggests that there may be abnormalities in frontal ph ospholipid metabolism in bipolar disorder. Functional studies have identifi ed affective state-related changes in cerebral glucose metabolism and blood flow, particularly in the prefrontal cortex during depression, but no clea r abnormalities specific to bipolar disorder have been consistently observe d. Conclusions: The current literature examining the neurophysiology of bipola r disorder using neuroimaging is limited. Nonetheless, abnormalities in spe cific frontal-subcortical brain circuits seem likely. Additional targeted s tudies are needed to capitalize on this burgeoning technology to advance ou r understanding of the neurophysiology of bipolar disorder.