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

Abstract

Background. Previous 31 P-MRS (magnetic resonance spectroscopy) studies suggested altered brain energy metabolism in bipolar disorder. This study characterized brain energy metabolism in lithium-resistant bipolar disorder using the photic-stimulation paradigm. Methods. Subjects were 19 patients with DSM-IV bipolar disorder (nine responders 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 occipital region was examined by 31 P-MRS during photic stimulation (PS). Six 31 P-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 disorder, lithium-resistant bipolar disorder, and control) was found for the phosphocreatine 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 comparison). Conclusions. The finding that phosphocreatine decreased after photic stimulation may be compatible with mitochondrial dysfunction. It is possible that mitochondrial function is impaired in lithium-resistant bipolar disorder.