Possible compensatory role of cerebellum in bipolar disorder. A cortical thickness study.

Recent studies suggested that structural changes in the cerebellum are implicated in the pathophysiology of bipolar disorder (BD). Here, we aimed to characterize the structural alterations of cerebellar lobules in BD, evaluating their possible relation with those occurring in the rest of the brain. One-hundred-fifty-five type I BD patients were recruited and compared with one-hundred-nineteen controls subjects. Cerebral cortical thickness (CT) was evaluated vertex-wise, while cerebellar CT at the level of its twelve lobules. A widespread pattern of cortical thinning was found in several clusters of BD patients. In the cerebellum, we found an anterior thinning (lobule I_II, III, X) and a posterior thickening (crus I, crus II, lobule VI and lobule IX) of its lobules in BD. Exploring the relation between cerebral and cerebellar CT changes in BD patients, after correcting for age and disease duration, the CT of a large subset of cerebral regions, found thinned in BD, were also inversely correlated with the thickening of cerebellar lobule IX. We speculate that this lobule may undergo adaptive changes to compensate the widespread cortical thinning which characterizes BD syndrome. Such a compensatory adaptation of the cerebellum would be similar to that found in other neurological and psychiatric disorders.