[Structural magnetic resonance imaging (MRI) studies in bipolar disorder]

To review structural MRI studies in bipolar disorder. A computer-assisted literature search of the Medline Ovid files for the period 1966 to November 2002 was performed, augmented by the use of articles meeting the criteria of this study from recent reviews. The studies included in this review show that there are abnormalities in the regions playing a role in the prefrontal-subcortical circuits that have been implicated in the pathophysiology of bipolar disorder, rather than generalized abnormalities like cerebral volume reduction or ventricular enlargement. The most widely studied and frequently reported finding of T2 signal hyperintensities is not considered to be specific to bipolar disorder. The findings of dorsolateral and subgenual prefrontal cortical volumetric reductions are in agreement with the findings of few neuropathological studies of bipolar disorder and suggest that prefrontal cortex plays an important role in the pathophysiology of the disorder. Among the medial temporal structures, the increase in amygdala volume seems to be specific to bipolar disorder. The findings in structures like the striatum and thalamus are conflicting, due to difficulties in the detailed measuring of the volumes of these structures with current techniques. Bipolar disorder is associated with brain abnormalities detected with structural MRI. Studies integrating structural neuroimaging methods with functional neuroimaging are needed to specifically determine how these abnormalities affect the function of these brain regions.