Background: Decreased callosal size and anisotropy have been described in schizophrenia patients but their longitudinal progression remains poorly understood.
Methods: We performed diffusion-tensor and structural magnetic resonance imaging at baseline and at follow-up four years later in 49 chronic schizophrenia patients and 16 healthy comparison subjects. Schizophrenia patients were subdivided into good-outcome (n=23) and poor-outcome (n=26) groups. Baseline-to-follow-up changes in size, shape, position and fractional anisotropy of the corpus callosum, divided into five sagittal sections and five rostro-caudal segments, were assessed.
Results: At baseline scan and in comparison to healthy subjects, schizophrenia patients displayed 1) smaller callosal size, 2) lower average anisotropy in all sagittal sections except the midline, and 3) more dorsal average coordinate position. During the four years after the baseline scan, patients with schizophrenia exhibited a more pronounced decline in absolute size of the corpus callosum than healthy comparison subjects. As compared with the good-outcome group, the corpus callosum in poor-outcome patients at baseline was of smaller size and lower average anisotropy, more elongated and posteriorly positioned. During the follow-up interval, poor-outcome patients displayed a more pronounced decline in size but less pronounced decline in anisotropy of the corpus callosum than patients with good outcomes.
Conclusions: Differences in callosal size between schizophrenia patients and healthy subjects seen at baseline continue to widen in the chronic phase of the illness, especially in patients with poor functional outcome. Baseline differences in callosal anisotropy among patients with different outcomes, however, diminish over time.