Hippocampal neurochemical pathology in patients at first episode of affective psychosis: a Proton Magnetic Resonance Spectroscopic Imaging Study

While several studies have suggested a relationship between the hippocampus and psychosis in schizophrenia, fewer studies have specifically investigated the presence of psychosis in mood disorders from a neurobiological perspective. Moreover, a limitation of these earlier studies is that the majority of them were performed in chronic patients. The present proton magnetic resonance spectroscopic imaging (1H-MRSI) study assessed neuronal integrity (as assessed with N-acetylaspartate, NAA) in the hippocampus of patients with a first episode of mood disorders with psychotic symptoms. We studied 17 patients and 17 healthy subjects matched for age and sex. Subjects underwent 1H-MRSI, and measures of NAA, choline-containing compounds (CHO), and creatine+phosphocreatine (CRE) in 11 brain regions were obtained, i.e. hippocampus (HIPPO), dorsolateral prefrontal cortex, superior temporal gyrus, inferior frontal gyrus, occipital cortex, anterior and posterior cingulate, centrum semiovale, prefrontal white matter, thalamus and putamen. NAA/CRE ratios in HIPPO of patients were significantly lower than in controls. Sporadic and non-hypothesis-driven results were found in occipital cortex and prefrontal white matter as a main effect of diagnosis, and in superior temporal gyrus as a hemisphere by diagnosis interaction. These results would not survive a Bonferroni correction for the number of ROIs. No correlations were found with the available demographic and clinical data. Therefore, hippocampal neuronal abnormalities are present at the onset of mood disorders with psychotic symptoms. These data suggest that neuronal abnormalities in HIPPO may be associated with psychosis in mood disorders. Since these data were obtained in patients at first episode, they cannot be explained by chronicity of illness or pharmacological treatment.