CHICAGO — Magnetic resonance spectroscopy can identify distinct abnormalities in the brain chemistry of patients with bipolar disorder, opening up the possibility for a definitive diagnostic test, John D. Port, M.D., said at the annual meeting of the Radiological Society of North America.
“We hope to eventually refine this into a clinically useful test that could shave years off a patient's time to diagnosis,” said Dr. Port of the department of radiology at the Mayo Clinic in Rochester, Minn.
Physicians “clearly [need] a tool to help diagnose bipolar disorder. We hope this technique will prove helpful by identifying metabolic markers of the disease,” he said.
Using a 3T long-bore MR scanner, which has twice the strength of scanners used in previous studies on bipolar disorder, the researchers scanned the brains of 21 patients with a clear diagnosis of bipolar disorder, and 21 healthy volunteers matched for age, sex, and dominant hand. The bipolar patients were medication naive and free of substance abuse.
Each scan took about 1 hour and enabled the analysis of 14 regions, and five metabolites within the brain tissue, Dr. Port said.
Compared with healthy individuals, bipolar patients had significantly different levels of certain metabolites in two brain areas that control behavior and movement.
In the right frontal white matter, myo-inositol was significantly increased, and in the right lentiform region, N-acetylaspartate, glutamate/glutamine, and creatine were significantly decreased in bipolar patients, compared with healthy normals, he told this newspaper.
In addition, the analysis was able to distinguish between various severities of bipolar disorder.
Patients with bipolar I illness had significantly lower choline levels in the left caudate region of the brain, compared with patients with bipolar II illness and bipolar illness not otherwise specified (BP-NOS).
Additionally, right anterior cingulate creatine levels were higher in bipolar I patients (BP-I), than in bipolar II (BP-II) patients.
And, finally, the researchers found differences in the right parietal white matter of BP-I patients, compared with other bipolar patients—a finding that they had not expected.
“BP-I patients had significantly higher levels of choline in their right parietal white matter, compared with BP-II patients, and more N-acetylaspartate in this region compared with BP-NOS patients,” Dr. Port said. “This was surprising to us, because until now, parietal white matter was not thought to be involved in psychiatric disease.”
Dr. Port said the pattern of metabolite abnormalities and locations form a “fingerprint” of bipolar disorder and its various subtypes. His research team, which includes two psychiatrists, is hoping to use this technique in the development of a diagnostic test. This will not only speed up the diagnosis of bipolar disorder, but might also help predict which patients would benefit from various treatments, he said.
An image of the brain of a bipolar disorder patient (upper left) is overlaid with a grid showing creatine levels (upper right). Yellow/gold areas have highest creatine levels. For a selected voxel (blue arrow), data confirm the creatine value. Courtesy Dr. John D. Port