Altered depth of the olfactory sulcus in first-episode schizophrenia

A shallow olfactory sulcus has been reported in chronic schizophrenia, possibly reflecting abnormal forebrain development during early gestation. However, it remains unclear whether this abnormality exists at the early illness stage and/or develops progressively over the course of the illness. This magnetic resonance imaging (MRI) study investigated the length and depth of the olfactory sulcus in 64 first-episode schizophrenia patients and 64 controls, of whom longitudinal MRI data (mean inter-scan interval=2.6 years) were available for 20 patients and 21 controls. In the cross-sectional comparison at the baseline, the schizophrenia patients had a significantly shallower olfactory sulcus compared with the controls bilaterally, but there was no group difference in its anterior-posterior length. A longitudinal comparison demonstrated that the sulcus length and depth did not change over time in either group. The olfactory sulcus measures of the patients did not significantly correlate with clinical variables such as onset age, medication or symptom severity. These findings suggest that the olfactory sulcus depth, but not length, may be a static vulnerability marker of schizophrenia that reflects early neurodevelopmental abnormality.