Hippocampal and parahippocampal volumes in schizophrenia: a structural MRI study

Abstract

Smaller medial temporal lobe volume is a frequent finding in studies of patients with schizophrenia, but the relative contributions of the hippocampus and three surrounding cortical regions (entorhinal cortex, perirhinal cortex, and parahippocampal cortex) are poorly understood. We tested the hypothesis that the volumes of medial temporal lobe regions are selectively changed in schizophrenia. We studied 19 male patients with schizophrenia and 19 age-matched male control subjects. Hippocampal and cortical volumes were estimated using a three-dimensional morphometric protocol for the analysis of high-resolution structural magnetic resonance images, and repeated measures ANOVA was used to test for region-specific differences. Patients had smaller overall medial temporal lobe volumes compared to controls. The volume difference was not specific for either region or hemisphere. The finding of smaller medial temporal lobe volumes in the absence of regional specificity has important implications for studying the functional role of the hippocampus and surrounding cortical regions in schizophrenia.

Fig. 1.

Four coronal slices through the medial temporal lobe demonstrating the parahippocampal subregions at the level of the (A) amygdala, (B) uncus, (C) body, and (D) tail of the hippocampus. (Entorhinal cortex in yellow, perirhinal cortex in orange, hippocampus in red and parahippocampal cortex in blue).

Fig. 2.

Mean and percentage volume differences between the two groups in the hippocampal and parahippocampal subregions (Abbreviations: ERC, entorhinal cortex; PHC, parahippocampal cortex; PRC, perirhinal cortex).