MRI features of clinical outcome in bipolar disorder: A selected review: Special Section on “Translational and Neuroscience Studies in Affective Disorders”. Section Editor, Maria Nobile MD, PhD. This Section of JAD focuses on the relevance of translational and neuroscience studies in providing a better understanding of the neural basis of affective disorders. The main aim is to briefly summaries relevant research findings in clinical neuroscience with particular regards to specific innovative topics in mood and anxiety disorders

Background: Bipolar disorder (BD) is a severe and disabling mental illness, which is characterized by selective gray matter (GM) and white matter (WM) brain alterations, as observed by several imaging studies. However, the clinical course of the disease is uncertain and can vary across BD patients, with some having a benign course and others a severe disability. In this perspective, magnetic resonance imaging (MRI) can help identifying biological markers of worse prognosis. Methods: The present selected review aimed at summarizing structural MRI (sMRI) studies exploring the correlation between brain morphology and features of clinical outcome, which could include treatment response, cognitive impairment and global functioning. Results: Overall, the results from the reviewed sMRI studies reported that WM hyperintensities and GM volume reductions, mainly in fronto-limbic areas, correlate with worse outcome in BD. However, the selected outcome measures vary across studies, thus these observations cannot be conclusive. Limitations: Heterogeneity across studies and inconsistency on the outcome measures adopted limit the conclusion of the present review. Absence of widely shared definitions of outcome should be object of further research on BD in order to indicate more stable features of illness course. Conclusions: In summary, WM hyperintensities and fronto-temporo-limbic GM alterations may be potential indices of worse outcome in BD patients, particularly in terms of illness severity and progression. The identification of stable markers of prognosis can help the clinicians in selecting subgroups of bipolar patients who need specific treatment to preserve cognitive / psychosocial functioning, in the light of personalized approaches. To further characterize outcome in BD, future sMRI studies should a) longitudinally investigate patients with either poor or good course of the disease, and b) correlate neuroimaging measures with clinical, cognitive and genetic markers.