Corpus callosum signal intensity in patients with bipolar and unipolar disorder.
BACKGROUND
Anatomical abnormalities in the corpus callosum have been reported in magnetic resonance imaging (MRI) studies in patients with bipolar but not unipolar disorder. MRI signal intensity can be used as a putative index of corpus callosum myelination.


OBJECTIVE
To measure MRI signal intensity in patients with bipolar and unipolar disorder to investigate abnormalities of corpus callosum myelination.


METHODS
The study involved 29 DSM-IV bipolar patients (mean (SD) age, 35 (11) years; 16 male, 13 female), 23 DSM-IV unipolar patients (41 (10) years; 4 male, 19 female), and 36 healthy controls (37 (10) years; 23 male, 13 female). A 1.5T GE Signa magnet was employed, with a fast spin echo sequence. Corpus callosum signal intensity was obtained blindly using the semiautomated software NIH Image 1.62.


RESULTS
Bipolar patients had lower corpus callosum signal intensity for all callosal subregions (genu, anterior and posterior body, isthmus, splenium) than healthy controls (ANCOVA, age and sex as covariates, p<0.05). No significant differences were found between unipolar and healthy subjects (ANCOVA, age and sex as covariates, p>0.05).


CONCLUSIONS
The findings suggest abnormalities in corpus callosum white matter in bipolar but not unipolar patients, possibly because of altered myelination. Such abnormalities could lead to impaired interhemispheric communication in bipolar disorder. Longitudinal MRI studies involving first episode and early onset bipolar patients will be necessary for a better understanding of the potential role of abnormalities of corpus callosum myelination in the pathophysiology of bipolar disorder.
Brambilla
P
P
Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pennsylvania, USA.
Nicoletti
M
M
Sassi
R B
RB
Mallinger
A G
AG
Frank
E
E
Keshavan
M S
MS
Soares
J C
JC
D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D003337:Corpus Callosum / Q000473:pathology* / Q000503:physiopathology*; D003866:Depressive Disorder / Q000175:diagnosis* / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009186:Myelin Sheath / Q000473:pathology; D009434:Neural Pathways / Q000503:physiopathology*