Schizophrenia with preserved insight is associated with increased perfusion of the precuneus

Background: Preserved insight into illness has been suggested to be predictive of outcome in patients with schizophrenia. We aimed to investigate the functional substrate underlying preserved insight in these patients. Methods: We recruited patients with paranoid schizophrenia and healthy controls matched for age and sex. Patients were grouped according to preserved or impaired insight into illness using the Scale to assess Unawareness of Mental Disorder (SUMD). Whole-brain technetium-99m ethyl cysteinate dimer single photon emission computed tomography regional cerebral blood flow was compared at the voxel level between the 2 groups using a statistical parametric map (voxel-level significance of p < 0.001, uncorrected; cluster level significance of p < 0.05, uncorrected). Results: We enrolled 31 right-handed patients with schizophrenia and 18 controls in our study. Twenty-one (67.7%) patients had preserved insight. The 2 groups did not differ significantly in demographic and clinical characteristics or in treatment. Compared with controls, the whole group of patients showed bilateral frontotemporal hypoperfusions, with no statistical difference between patients with preserved or impaired insight for these areas. Patients with preserved insight showed significantly increased perfusion of the bilateral precuneus relative to those with impaired insight. Limitations: Patients with subtypes other than paranoid schizophrenia have to be investigated to assess whether involvement of the precuneus in patients with preserved insight can be identified across the full spectrum of subtypes and symptoms of schizophrenia. Moreover, our study concerned only the central dimension (awareness of mental disorder) of 1 scale (SUMD); other dimensions of insight could be studied. Conclusion: Our results show that schizophrenia with preserved insight is associated with greater perfusion of the precuneus, a brain area known to be involved in self-consciousness, suggesting a compensatory mechanism of frontotemporal impairment.