Neural markers of remission in first-episode schizophrenia: A volumetric neuroimaging study of the hippocampus and amygdala

Abstract 

Objective

The temporolimbic region has been implicated in the pathophysiology in schizophrenia. More specifically, significantly smaller hippocampal volumes but not amygdala volumes have been identified at onset in first-episode schizophrenia (FES) patients. However, volumetric differences (namely, in the hippocampus) exhibit an ambiguous relationship with long-term outcome. So, we examined the relationship between hippocampus and amygdala volumes and early remission status.

Methods

We compared hippocampus and amygdala volumes between 40 non-remitted and 17 remitted FES patients and 57 healthy controls. Amygdala and hippocampus were manually traced with the hippocampus additionally segmented into three parts: body, head, and tail. Remission was defined as mild or less on both positive and negative symptoms over a period of 6 consecutive months as per the 2005 Remission in Schizophrenia Working Group criteria.

Results

A significant [group×structure×side] interaction revealed outcome groups differed in hippocampus tail volumes; significantly on the left (non-remitted=694±175 mm³; remitted=855±133 mm³; p=0.001) with a trend difference on the right (non-remitted=723±162 mm³; remitted=833±126 mm³; p=0.023). Groups did not differ in body, head, or amygdala volumes bi-laterally.

Conclusions

A smaller hippocampal tail volume may represent a neural marker in FES patients who do not achieve early remission after the first 6months of treatment. The early identification of patients with poor outcome with respect to the hippocampus tail may encourage the search for new, more target-specific, medications in hope of improving outcome and moving us towards a better understanding of the pathophysiology of schizophrenia.

Abbreviation: FES, first-episode schizophrenia

Keywords: First-episode schizophrenia, Hippocampus, Amygdala, Remission, Structural MRI, Neuroimaging