Proton Magnetic Resonance Spectroscopy (1H MRS) of the Hippocampal Formation in Schizophrenia: A Pilot Study

Abstract

Background: Recent post-mortem and magnetic resonance imaging (MRI) studies strongly suggest a decrease in the volume of the hippocampus and other limbic temporal structures in schizophrenia. Therefore, we hypothesised that N-acetyl aspartate (NAA) which is found mainly in neurons and which can be measured by proton magnetic resonance spectroscopy (¹H MRS) would be decreased in the limbic temporal region in schizophrenia.Method: Consenting subjects fulfilling DSM-III-R criteria for schizophrenia (n = 11) and matched healthy volunteers (n = 11) who were recruited in a tertiary university referral centre, participated in a ¹H MRS brain study. Proton MRS spectra were obtained from a 12 cm³ voxel (2 × 2 × 3 cm) in the right and left hippocampus/amygdala region. A researcher blind to the source of the spectra, measured the NAA intensity in all subjects, which were then statistically compared across the two groups.Results: NAA intensities were significantly reduced in the right hippocampus/amygdala region of schizophrenic patients (P = 0.038). The difference of the left side did not reach significance at the 95% confidence level.Conclusions: The findings of decreased NAA in this study suggest that there may be a decrement in neuronal number or tissue volume of the right hippocampal/amygdala region in schizophrenia. Biochemical alterations in the metabolism of NAA in schizophrenia may be an alternative explanation. The findings are consistent with other types of post-mortem and in vivo evidence for hypoplasia of the limbic temporal structures in schizophrenia, postulated to be of neurodevelopmental pathogenesis.