White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study.
OBJECTIVE
An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects.


METHODS
Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum.


RESULTS
Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls.


CONCLUSIONS
Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.
Department of Psychiatry, Harvard Medical School, Boston, MA, USA. ytodd@mclean.harvard.edu
Deborah A
DA
Yurgelun-Todd
Marisa M
MM
Silveri
Staci A
SA
Gruber
Michael L
ML
Rohan
Patricia J
PJ
Pimentel
D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis / Q000503:physiopathology*; D001921:Brain / Q000033:anatomy & histology* / Q000503:physiopathology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index