Abstract
Objective: To examine the possible presence of white matter abnormalities and apparent diffusion coefficient (ADC) changes by using diffusion-weighted magnetic resonance (MR) imaging, in patients with euthymic bipolar I disorder.
Method: Thirty patients (12 women, 18 men) were included in this study. The patients, whose total Young Mania Rating Scale points were 5 or less at least for four weeks, and whose total Hamilton Depression Rating Scale points were 7 or less were considered as euthymic. The control group was consisted of age and gender matched 30 healthy individuals. ADC values were obtained symmetrically from the frontal, temporal, and occipital lobes and the genu of the corpus callosum, where white matter tissue was the largest.
Results: The mean ADC value of the bipolar group was determined as 856.53±88.31x10-3mm/s, and that of the control group was 778.89±89.67x10-3mm/s. The mean ADC values on the right frontal area was found to be lower in bipolar patients as compared to that of the control group, but the difference was statistically insignificant. However, it was found significantly lower on the left hemisphere (p<0.05). The increases of the mean ADC values obtained from both right and left temporal and occipital lobes of bipolar group were found to be statistically significant as compared to those of the control group (p<0.05).
Conclusions: According to the results of this study, the increased ADC values in euthymic bipolar patients may probably be related to the disintegration of white matter. Besides, decreased ADC values obtained from the frontal areas suggest that the disintegration might be reversible.

Key words: diffusion-weighted imaging, euthymia, white matter