MRI study of posterior fossa structures and brain ventricles in bipolar disorder patients

Previous brain imaging studies have suggested anatomical abnormalities in posterior fossa structures and brain ventricles in bipolar patients. Such abnormalities could possibly be implicated in the pathophysiology of bipolar disorder. Twenty-two DSM-IV bipolar outpatients (mean age+/-S.D.=36+/-10 years) and 22 healthy controls (mean age+/-S.D.=38+/-10 years) underwent an 1.5T MRI (3D-gradient echo-imaging SPGR), performed in the coronal plane (TR=25 ms, TE=5 ms, slice thickness=1.5 mm). The brain structures of interest were traced blindly with a semi-automated software. No significant differences were found between bipolar patients and healthy controls for any posterior fossa measures, or for measures of third or lateral ventricles (MANOVA, age covariate, P>0.05). Age was directly correlated with 3rd ventricle volumes in bipolar patients (Pearson correlation coefficient=0.458, P=0.032), but not in healthy controls (Pearson correlation coefficient=0.313, P=0.155). There was a significant direct correlation between the number of prior illness episodes and right lateral ventricle volumes (Partial correlation coefficient=0.658, P=0.011). Familial patients had smaller left and right cerebellar hemispheres and total vermis volumes, and larger left lateral ventricle volumes compared with non-familial ones (MANOVA, age covariate, P<0.05). In this preliminary study, we were not able to replicate previous findings of abnormalities in cerebellum or brain ventricles in bipolar individuals. However, there were suggestions that abnormalities in cerebellum, vermis, and lateral ventricle sizes may be present in familial cases of the disorder, which should be further examined in future studies with larger patient samples.