Prevalence of large cavum septi pellucidi in ultra high-risk individuals and patients with psychotic disorders.

An increased prevalence of large cavum septum pellucidum (CSP), a marker of midline neurodevelopmental abnormality, has been reported in schizophrenia. However, not all studies have been able to replicate this finding and very few studies have been conducted in large samples. In the current study, magnetic resonance imaging was used to assess the presence of an abnormal CSP in 162 patients with first-episode psychosis (FEP), 89 patients with chronic schizophrenia, 135 ultra high-risk (UHR) individuals, and 87 controls. The prevalence of a large CSP (>5.6 mm) did not differ between the groups (9.3% of the FEP patients, 11.2% of the chronic schizophrenia patients, 11.1% of the UHR individuals, and 11.5% of the controls). The length of the CSP was not associated with sulcal morphology of the anterior cingulate cortex (ACC), suggesting different biological processes responsible for the CSP enlargement versus ACC folding. These findings suggest that the CSP is not a neurodevelopmental marker of psychosis and cast doubt over the notion that it plays a major role in the neurobiology of psychosis.