Alterations of the cerebellum and basal ganglia in bipolar disorder mood states detected by quantitative T1 mapping

ObjectivesQuantitative mapping of T1 relaxation in the rotating frame (T1) is a magnetic resonance imaging technique sensitive to pH and other cellular and microstructural factors, and is a potentially valuable tool for identifying brain alterations in bipolar disorder. Recently, this technique identified differences in the cerebellum and cerebral white matter of euthymic patients vs healthy controls that were consistent with reduced pH in these regions, suggesting an underlying metabolic abnormality. The current study built upon this prior work to investigate brain T1 differences across euthymic, depressed, and manic mood states of bipolar disorder. MethodsForty participants with bipolar I disorder and 29 healthy control participants matched for age and gender were enrolled. Participants with bipolar disorder were imaged in one or more mood states, yielding 27, 12, and 13 imaging sessions in euthymic, depressed, and manic mood states, respectively. Three-dimensional, whole-brain anatomical images and T1 maps were acquired for all participants, enabling voxel-wise evaluation of T1 differences between bipolar mood state and healthy control groups. ResultsAll three mood state groups had increased T1 relaxation times in the cerebellum compared to the healthy control group. Additionally, the depressed and manic groups had reduced T1 relaxation times in and around the basal ganglia compared to the control and euthymic groups. ConclusionsThe study implicated the cerebellum and basal ganglia in the pathophysiology of bipolar disorder and its mood states, the roles of which are relatively unexplored. These findings motivate further investigation of the underlying cause of the abnormalities, and the potential role of altered metabolic activity in these regions.