Although people that suffer from the two kinds of bipolar disorder, Type I and Type II, share some of the same symptoms, there are significant differences in the structure of their brains.
Jerome Maller, PhD, of Monash University, Melbourne, Australia, used MRI scans to examine the brains of 16 Type I and 15 type II bipolar patients, plus another 31 healthy control subjects. Type I is considered a more severe form of the disorder. They wanted to see if there were differences in the subjects’ brains in terms of gray matter, white matter and cerebrospinal fluid.
Overall, there was less total brain volume — gray and white matter combined — and more cerebrospinal fluid volume in bipolar patients than in healthy controls. However, Type II patients’ brains were essentially the same as controls’ brains, while Type I patients had relatively higher volume in the caudate nucleus and other areas associated with reward processing and decision making, the researchers reported in the Journal of Affective Disorders.
Also, a new technology known as diffusion tensor imaging, which is used to measure the integrity of white matter, showed that while the integrity in both types of bipolar patients was reduced compared with controls, the impact was stronger among those with Type II, particularly in the frontal and prefrontal cortex. This could indicate that Type II bipolar disorder may be the result of cognitive dysfunction.
While people with Type I and the less-severe Type II bipolar disorder share some of the same symptoms, there are significant differences in the physical structure of their brains. Type I sufferers have somewhat smaller brain volume, researchers report in the Journal of Affective Disorders, while those with Type II appear to have less robust white matter.
Overall, there was less total brain volume — gray and white matter volume added together — and more cerebrospinal fluid volume in bipolar patients than in healthy controls, consistent with other recent studies suggesting a connection between brain volume and depression.