Hippocampal volume in subjects at high risk of psychosis: a longitudinal MRI study.

Introduction: The hippocampal formation has been studied extensively in schizophrenic psychoses and alterations in hippocampal anatomy have been consistently reported. Chronic schizophrenia seems to be associated with bilateral hippocampal volume (HV) reduction, while in patients with an at-risk mental state (ARMS) there are contradictory results. This is the first region of interest (ROI) based follow-up MRI study of hippocampal volume comparing ARMS individuals with and without transition to psychosis. The aim was to investigate the timing of HV changes in ARMS in the early phase of psychosis.

Methods: Magnetic resonance imaging data from 18 antipsychotic-naïve individuals with an ARMS were collected within the FePsy-clinic for early detection of psychoses. During follow-up 8 subjects transitioned to psychosis (ARMS-T) and 10 did not (ARMS-NT). Subjects were re-scanned after the onset of psychosis or at the end of the follow-up if they did not develop psychosis.

Results: Across both groups there was a significant decrease in HV over time (p<0.05). There was no significant difference in progression between ARMS-T and ARMS-NT. Antipsychotic medication at follow up was associated with increased HV (p<0.05).

Conclusions: We found a decrease of HV over time in subjects with an ARMS, independently of clinical outcome. We may speculate that the decrease of HV over time might reflect brain degeneration processes.