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

BACKGROUND: Previous 31P-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 nonresponders, 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 31P-MRS during photic stimulation (PS). Six 31P-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.