Bipolar Depression Before and After Lamotrigine Treatment

Depression is the predominant prevailing mood state in bipolar disorder and bipolar depression is associated with substantial morbidity and mortality. However, in comparison to acute mania, bipolar depression is understudied both from the standpoint of its pathophysiology as well as clinical trials which include FDA-approved treatments. Given this lack of evidence to base guidelines, clinicians and patients are limited as to how best to treat the depressive phase of the illness. Proton magnetic resonance spectroscopy (1H-MRS) is a valuable, non-invasive method to study in-vivo brain biochemistry. Of the novel imaging paradigms, MRS is uniquely positioned to investigate biochemical mechanism of drug action that is objectively measurable and clinically relevant. As there is increasing interest in glutamatergic dysregulation in mood disorders, this project will utilize 1H-MRS to study glutamate and glutamine levels in brain regions implicated in bipolar disorder (anterior cingulate and dorsolateral prefrontal cortex). This was a 5-year single-site study of bipolar depression utilizing 1H-MR spectroscopy before and after treatment with lamotrigine. At baseline bipolar depressed subjects and age-matched controls underwent a 1H-MRS at Mayo Clinic in Rochester, Minnesota. The bipolar depressed subjects were then be placed on 12-week, open evaluation of lamotrigine monotherapy. After 12 weeks, the bipolar subjects underwent a second 1H-MRS scan. Two different MRS sequences were used to measure the brain chemicals in a single 2 x 2 x 2 cm cube located in the center of anterior cingulate cortex: an intermediate echo-time PRESS sequence and a 2D J-resolved averaged PRESS sequence. Spectroscopic data were inspected for quality; subjects whose data were contaminated by artifact were excluded from the study. Spectra were then processed using LCModel to quantify brain chemical levels. Regular brain MRI images were segmented, yielding a map of the amount of CSF in the head. The MRS cube was overlaid onto the CSF map and the fraction of CSF within the cube measured. This measurement was used to "remove" the CSF from the MRS cube giving brain chemical concentrations. The concentrations were then used for statistical analysis. Note: All of the spectroscopy data are expressed in Institutional Units (IU).