Selective bilateral hippocampal volume loss in chronic schizophrenia

Background: The hippocampus is implicated in the pathophysiology of schizophrenia; however, volumetric changes are subtle and have limited diagnostic specificity. It is possible that the shape of the hippocampus may be more characteristic of schizophrenia. Methods: Forty-five patients with chronic schizophrenia and 139 healthy control subjects were scanned using magnetic resonance imaging. Hippocampi were traced manually, and two-dimensional shape information was analyzed. Results: Two shape factors were found to be adequate to represent variance in the shape of the hippocampus. One of these factors, representing volume loss behind the head of the hippocampus, provided a degree of discrimination between patients with chronic schizophrenia and healthy control subjects; however, overall hippocampal volume following appropriate adjustment for brain volume showed a similar level of discrimination. Patients with chronic schizophrenia were best characterized using these two measures together, but diagnostic specificity was only moderate. Conclusions: This study identified that less of the hippocampus was distributed in its posterior two-thirds in patients with chronic schizophrenia, and specifically in the region just posterior to the hippocampal head. Group discrimination on the basis of hippocampal volume and shape measures was moderately good. A full three-dimensional analysis of hippocampal shape, based on large samples, would be a useful extension of the study.