A Diffusion Tensor Imaging Study Of Pediatric Bipolar Disorder

Objectives: Pediatric bipolar disorder (PBD) is a common and severe psychiatric disorder with high levels of morbidity and mortality. Presently, some functional imaging studies have shown fronto-temporal/limbic, fronto-parietal and fronto-striatal dysfunction underlying the affective and cognitive psychopathology in pediatric and adult bipolar patients. Therefore, our goal was to study the microstructural abnormalities directly using diffusion tensor imaging (DTI) with its three parameters: fractional anisotropy (FA), apparent diffusion coefficient (ADC), and new developed regional coherence index (r-FCI) in specific white matter fiber tracts that connect the structures underlying these functional abnormalities.Materials and Methods: Threeteen patients with PBD met the 1998 Washington University Schedule for Affective Disorders and Schizophrenia and DSM-IV criteria for bipolar disorder and equal number of age, gender, IQ, and race matched healthy controls were recruited for this study under an IRB approved protocol. DTI scans were performed on a GE 3T Signa MRI scanner. Regions of interest analyses were performed on the following five white matter fiber tracts connecting the medial pre-frontal, temporal, occipital and parietal regions: anterior region of corona radiata (ACR), posterior limb of internal capsule (PLIC), cingulum (CG), superior longitudinal fasciculus (SLF), and inferior longitudinal fasciculus (ILF), and three DTI parameters, FA, ADC and r-FCI were examined. Student's t-tests were used to evaluate the difference in these three parameter values between PBD patients and the controls a confidence level of no less than 95%.Results: The bipolar patient group showed significantly decreased FA in ACR and ILF as compared with the control group (t>4.01, P<0.001). ACR, ILF, and SLF also exhibited significantly higher ADC values in bipolar patients than the healthy controls (t>1.91, P<0.05). A moderate difference in FCI (t=1.74, P=0.05) was also observed in ACR. No significant difference was seen in the FA values of PLIC, CG, and SLF, the ADC values of PLIC, and CG, and the FCI values of PLIC, CG, SLF, and ILF. Conclusions: white matter involvement and abnormality were observed in a number of tracts (e.g., ACR, ILF and SLF) connecting the fronto-temporal, temporo-occipital, or fronto-parietal areas in PBD patients. The results revealed by DTI confirmed and complemented the published functional magnetic resonance imaging findings that showed abnormal neuronal activation in the aforementioned brain regions. DTI may provide a tool to evaluate PBD patients, gain better understanding of the underlying pathophysiology, and ultimately serve as a biomarker for the PBD recognition and treatment prediction.