Decreased brain intracellular pH measured by ³¹P-MRS in bipolar disorder: A confirmation in drug-free patients and correlation with white matter hyperintensity

The authors have previously reported decreased intracellular pH (pHi) in the frontal lobes in euthymic bipolar patients treated with lithium using ³¹P-MRS. White matter hyperintensity (WMHI) is frequently seen in bipolar disorder. To examine a possible effect of lithium on pHi and the relationship between pHi and WMHI, seven drug-free euthymic bipolar patients were examined, and T₂-weighted MRI were examined in 14 previously reported bipolar patients. Drug-free patients showed significantly lower pHi than controls. WMHI was associated with low pHi and increased phosphodiester peak. These results suggest that decrease of pHi is not an effect of lithium but is instead related to the pathophysiology of illness. Decrease of pHi and increase of the PDE peak may be the biochemical basis of WMHI in bipolar disorder.