MRI reveals cerebellum’s possible role in bipolar disorder

Chuck Bednar for redOrbit.com – Your Universe Online

By using a different type of MRI imaging scan, researchers have located previously undetected differences in the brains of patients suffering from bipolar disorder, a psychiatric conditions that affects approximately one percent of the population.

Writing in the January 6 edition of the journal Molecular Psychiatry, University of Iowa psychiatry professor John Wemmie and his colleagues explained that they were able to locate differences in the white matter of patients’ brains and in the cerebellum, a region of the brain that had not previously been associated with the disorder.

Their examinations, which involved 15 patients with bipolar disorder and 25 control subjects, also found that these cerebellar differences were not present in patients that were taking lithium, the most commonly prescribed treatment for bipolar disorder.

In a statement, Wemmie explained that the new imaging technique “appears to be sensitive to things that just have not been imaged effectively before. So it’s really providing a new picture and new insight into the composition and function of the brain [in bipolar disorder].”

Bipolar disorder is characterized from sudden mood shifts from normal (euthymic) to depressed or manic states. For the new study, the patients were all in normal mood state when their brains were scanned using an MRI approach known as quantitative high-resolution T1 rho mapping, a technique sensitive to some byproducts of cell metabolism such as acidity in the brain.

In comparison with the brains of control subjects, elevated MRI signals were found in the cerebral white matter and the cerebellar region of patients affected by bipolar disorder. This signal could be the result of either a reduction in pH or a reduction in glucose concentration, both of which are factors influenced by cell metabolism, the study authors noted.

While previous research has suggested that abnormal cell metabolism may play a role in bipolar disorder, investigation of these abnormities has been hampered by the lack of imaging tools that are capable of detecting them.

Most available methods are slow, low-resolution and force scientists to identify the region of interest prior to beginning the research process, they added. Quantitative high-resolution T1 rho mapping, on the other hand, can quickly acquire a quality image of the entire brain.

The newly published study marks the first time that this imaging approach has been used to investigate a psychiatric disease, the researchers said, and the whole-brain technique reveals that a portion of the brain that researchers had never selected as a area of study could actually play a key role in bipolar disorder.

Casey Johnson, a postdoctoral researcher at the University of Iowa and first author on the study, said that his team’s work “was essentially exploratory. We didn’t know what we would find. The majority of bipolar disorder research has found differences in the frontal region of the brain. We found focal differences in the cerebellum, which is a region that hasn’t really been highlighted in the bipolar literature before.”

On the heels of their discovery, the researchers extensively reviewed scientific literature pertaining to bipolar disorder, and found several pieces of evidence supporting the notion that the cerebellum may be functioning abnormally in these patients. Furthermore, they found that lithium could potentially target this part of the brain, altering glucose levels there.

“Our paper, with this new technique, starts to bring all these pieces of evidence together for the first time,” Johnson said. The study authors are hopeful that the information provided by the new imaging technique could ultimately improve their understanding of the underlying abnormalities responsible for bipolar disease, as well as the development of better treatment options.

“If lithium’s effect on the cerebellum is the key to its effectiveness as a mood stabilizer, then a more targeted treatment that causes the same change in the cerebellum without affecting other systems might be a better treatment for patients with bipolar disorder,” said Wemmie.

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