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 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 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.