Reduced concentrations of N-acetylaspartate (NAA) and the NAA-creatine ratio in the basal ganglia in bipolar disorder: a study using 3-Tesla proton magnetic resonance spectroscopy.

The N-acetylaspartate (NAA) peak is prominent in the proton magnetic resonance spectrum and is thought to reflect neuron loss or dysfunction. This study was conducted to explore NAA biochemistry and its clinical correlates in mania. Subjects comprised 16 manic patients and 17 controls who underwent a structured diagnostic interview and (1)H magnetic resonance spectroscopy (MRS) acquisition. STEAM (1)H MRS (TR/TE/TM=2000/20/8 ms) was acquired at 3 Tesla from 2 x 2 x 2 cm(3) voxels in anterior cingulate (AC), right basal ganglia (BG), and left occipital-parietal white matter (OP). Absolute metabolite concentrations and ratios to creatine were calculated using the LC Model. The mean absolute concentrations of NAA and NAA-creatine ratio in the BG were significantly lower in manic subjects than in controls. There was a significant inverse correlation between NAA in the BG and the number of prior hospitalizations for mania. These data suggest BG pathology in mania and that NAA decrements may mark prior manic episode burden. Limitations of this study include small sample size and lack of tissue segmentation. Further study is encouraged to clarify state vs. trait aspects of NAA in bipolar disorder.