Altered brain energy metabolism in lithium-resistant bipolar disorder detected by photic stimulated P-31-MR spectroscopy

Background, Previous P-31-MRS (magnetic resonance spectroscopy) studies sug gested altered brain energy metabolism in bipolar disorder. This study char acterized brain energy metabolism in lithium-resistant bipolar disorder usi ng the photic-stimulation paradigm. Methods. Subjects were 19 patients with DSM-IV bipolar disorder (nine respo nders and 10 non responders, 13 with bipolar I and six with bipolar II) in the euthymic state and 25 healthy volunteers. Energy metabolism in the occi pital region was examined by P-31-MRS during photic stimulation (PS). Six P -31-MR spectra were obtained, one was before PS (Pre), two during 12 min of PS (PS1, PS2), and three after the PS (Post 1, Post 2, Post 3). Results. Significant effect of diagnosis (lithium-responsive bipolar disord er, lithium-resistant bipolar disorder, and control) was found for the phos phocreatine peak area ratio during the course of the photic stimulation (P < 0.05 by repeated measures ANOVA). The phosphocreatine peak area ratio was significantly decreased at Post 1 and Post 2 compared with Pre in lithium- resistant bipolar patients (P = 0.01 and P = 0.01 by Dunnett's multiple com parison). Conclusions, The finding that phosphocreatine decreased after photic stimul ation may be compatible with mitochondrial dysfunction. It is possible that mitochondrial function is impaired in lithium-resistant bipolar disorder.