Neurochemical pathology in hippocampus in euthymic patients with bipolar I disorder

Abstract

Subcortical regions such as hippocampus, thalamus and ventral putamen are assumed to be involved in the pathophysiology of mood regulation. Disturbed hippocampal neuronal function indicated by reduced N-acetyl-aspartate (NAA) levels in bipolar patients was shown by several studies. Results in thalamus and putamen are inconsistent. N-acetyl-aspartate, choline (Cho), creatine (Cr) and myo-inositol (Ins) were measured in left hippocampus, left thalamus and left putamen using proton magnetic resonance spectroscopy in 13 euthymic patients with bipolar I disorder and 13 pairwise matched healthy control subjects. Metabolic ratios NAA/Cr, NAA/Cho, Cho/Cr and Ins/Cr were calculated. Patients with bipolar I disorder demonstrated significantly reduced NAA/Cr in the left hippocampus compared with healthy control subjects. No alterations were found in thalamus or putamen. We hypothesize that this NAA/Cr reduction might reflect neuronal dysfunction in the left hippocampus in patients with bipolar disorder.