[Magnetic resonance spectroscopy (MRS) applications in bipolar disorder]

Magnetic resonance spectroscopy (MRS) is a noninvasive in vivo imaging technique that can directly assess the living biochemistry in localized brain regions without involving ionizing radiation. This review provides a brief description of spectroscopy, followed by a literature review of the key spectroscopy findings in bipolar disorder.

We conducted a Medline literature review for the period 1966-2003, and included all the controlled studies using MRS in bipolar disorder, as well as other relevant papers with important findings.

Studies showed an increase in choline (Cho) levels in basal ganglia and cingulate, and a decrease in dorsolateral prefrontal cortical (DLPFC) and hippocampal N-acetyl aspartate (NAA) levels. Frontal lobe phosphomonoester (PME) levels were decreased in the euthymic state and were higher in the manic and depressive states. Myoinositol (mI) was reduced by lithium treatment and this decrease was positively correlated with treatment response.

The findings from MRS studies of bipolar disorder demonstrate alterations in the neurochemistry of key brain regions participating in the fronto-limbic-subcortical circuits implicated in the pathophysiology of the disorder. These findings suggest abnormalities of the membrane phospholipid metabolism, cellular energy metabolism and myelin formation /maintenance in the DLPFC, cingulate, hippocampus and basal ganglia in bipolar disorder. Further studies are needed to distinguish between the changes that are due to the pathophysiology of bipolar disorder and those due to the effects of medications.