Hippocampal pathology in schizophrenia: magnetic resonance imaging and spectroscopy studies

The hippocampus is a site of previously reported structural and functional abnormalities in schizophrenia. We used magnetic resonance imaging(MRI) and proton magnetic resonance spectroscopy (MRS) to measure gray matter volume s, the neuronal marker N-acetylaspartate (NAA), and the combination of glut amate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA), designate d Glx. Measurements were obtained of the medial temporal lobe, centered on the hippocampus, in 10 male patients with schizophrenia (3 neuroleptic-medi cated and 7 medication-free), and 10 matched normal volunteers. MRI volumet ric measurements and MRS data obtained with short echo time (TE = 20 ms) on e-dimensional STEAM chemical shift imaging (CSI) on a GE 1.5 Tesla Signa sy stem were analyzed. A laterality index [(L-R)/(L + R)] was generated from t he ratio of Glx to choline-containing compounds (Cho) to test asymmetry cha nges. Reliability of the MRS measures was assessed with five test-retest st udies of healthy volunteers and showed coefficients of variation (CV) in th e range of 36-44% for the MRS ratios and standard deviations (S.D.) of 0.15 -0.17 for the laterality indices. The Glx/Cho laterality index showed a rel ative right-sided excess in this region in the patients (-0.23 +/- 0.20) co mpared to the controls (+0.06+/-0.20), which was not confounded by tissue c omposition or placement variability of the MRS voxels. Hippocampal volume d eficit and asymmetry were not significant, and other MRS measures showed no differences between patients and controls. The preliminary finding of a la teralized abnormality in Clx is consistent with postmortem findings of asym metric neurochemical temporal lobe abnormalities in schizophrenia. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.