Neuroradiology - Original Article
A combined VBM and DTI study of schizophrenia: bilateral decreased insula volume and cerebral white matter dysintegrity corresponding to subinsular white matter projections unbound to clinical symptomatology
Department of Radiology, Koç University School of Medicine, İstanbul, Turkey
Department of Psyciatry, Koç University School of Medicine, İstanbul, Turkey
Hulusi Behçet Life Sciences Research Center, İstanbul University İstanbul School of Medicine, İstanbul, Turkey
Department of Psyciatry, Gazi University School of Medicine, Ankara, Turkey
Department of Radiology, Gazi University School of Medicine, Ankara, Turkey
Diagn Interv Radiol ; : -
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Purpose: Grey matter and white matter changes within brain are well defined in schizophrenia. Most of the studies focused on either grey matter changes or white matter integrity separately and only in limited number of studies these changes are interpreted in the same frame. In addition, the relationship of these findings with clinical variables is not established clearly. Here we aimed to replicate the grey matter and white matter changes in a … (our origin) sample of schizophrenia patients and exhibit the relation of these imaging findings with clinical variables.
Methods: 20 schizophrenia patients and 16 matched healthy controls underwent MRI to investigate the grey matter and white matter alterations that occur in schizophrenia patients using voxel-based morphometry (VBM) and whole brain voxel-wise analysis of fractional anisotropy (FA), axial (AD), mean (MD) and radial (RD) diffusivity with SPM8. While the pre-processing steps of VBM were performed with the default parameters of VBM8 toolbox, the preprocessing steps of DTI were carried out using FSL. Additionally, VBM results were correlated with clinical variables. Significant between-group differences of diffusion metrics were reported using a (voxel-wise) cluster forming height threshold of family-wise error (FWE) uncorrected p value less than 0.0005 combined with a cluster-level FWE correction for multiple comparisons, while grey matter differences were reported at both cluster forming (p<0.05) and cluster level (p<0.01) FWE-correction.
Results: Bilateral insula showed decreased grey matter volume in schizophrenia patients when compared to healthy controls (p<0.01). The opposite contrast did not show a significant difference. None of the assessed clinical variables, as SANS, SAPS, GAF scores, duration of illness and age were correlated with the decreased grey matter volume of insula in schizophrenia patients (p>0.05). DTI analysis revealed a significant increase in MD, RD and AD, mainly on the fibers of bilateral anterior thalamic radiation and superior longitudinal fasciculus with left predominance, which intersected with bilateral subinsular white matter (p<0.05).
Conclusion: Based on the findings of this individual study, we suggest that insula may be the mainly affected brain region in schizophrenia, which is also well supported by literature. Our results were independent of the disease duration and schizophrenia symptoms. White matter alterations were observed within bilateral anterior thalamic radiation and superior longitudinal fasciculus that intersects with subinsular white matter. This finding should be supported by studies with larger sample sizes and more detailed clinical assessments in order to understand the function of insula in the neurobiology of schizophrenia.