Use of Z-Scores and Percentages to Assess Structural Brain MRI Findings in Patients With Schizophrenia

Schizophrenia is associated with structural brain abnormalities, although findings have been inconsistent. This study aimed to investigate global and regional volumetric measures in patients with schizophrenia using an automated volumetric analysis tool.

Eighty-one patients with schizophrenia or schizoaffective disorder (aged 18-65 years) underwent brain MRI on a 3T Siemens scanner using a high-resolution 3D T1-weighted MPRAGE sequence. Volumetric analysis was performed with vol2Brain, providing intracranial volume-adjusted percentages and normative z-scores. Group mean values were compared with normative data. One sample t-test was used as well as exploratory t-tests to examine sex differences, while Pearson correlations assessed associations with age.

Patients showed decreased brain tissue volumes relative to normative values. Mean white matter (z = -1.12) and gray matter (z = -0.55) were reduced, while cerebrospinal fluid was increased (z = +1.75). Cortical gray matter was moderately decreased (z = -0.77), whereas cerebellar gray matter was relatively preserved (z = +0.19) but displayed high variability. No significant sex differences were observed. Age correlated significantly with volumetric percentages but not with z-scores, suggesting parallel age-related changes in patients and controls.

Patients with schizophrenia demonstrated widespread reductions in brain tissue volumes and enlarged CSF spaces, consistent with previous literature. Preservation and variability of cerebellar gray matter highlight the heterogeneity of structural alterations. Automated volumetry offers a reproducible approach for characterizing brain morphology in schizophrenia and may support future efforts to define patient subgroups.