Overlapping and distinct gray and white matter abnormalities in schizophrenia and bipolar I disorder

Abstract

Background Schizophrenia and bipolar disorder may share common neurobiological mechanisms, but few studies have directly compared gray and white matter structure in these disorders. We used diffusion-weighted magnetic resonance imaging and a region-of-interest based analysis to identify overlapping and distinct gray and white matter abnormalities in 35 patients with schizophrenia and 20 patients with bipolar I disorder in comparison to 56 healthy volunteers. Methods We examined fractional anisotropy within the white matter and mean diffusivity within the gray matter in 42 regions-of-interest defined on a probabilistic atlas following non-linear registration of the images to atlas space. Results Patients with schizophrenia had significantly lower fractional anisotropy in temporal (superior temporal and parahippocampal) and occipital (superior and middle occipital) white matter compared to patients with bipolar disorder and healthy volunteers. In contrast, both patient groups demonstrated significantly higher mean diffusivity in frontal (inferior frontal and lateral orbitofrontal) and temporal (superior temporal and parahippocampal) gray matter compared to healthy volunteers, but did not differ from each other. Discussion Our study implicates overlapping gray matter frontal and temporal lobe structural alterations in the neurobiology of schizophrenia and bipolar I disorder, but suggests that temporal and occipital lobe white matter deficits may be an additional risk factor for schizophrenia. Our findings may have relevance for future diagnostic classification systems and the identification of susceptibility genes for these disorders.

Hemispheric lateralization abnormalities of the white matter microstructure in patients with schizophrenia and bipolar disorder

“…In these regions, the micro structural abnormalities were more prominent in the right than in the left hemisphere in patients with BD. The finding of more severe microstructural abnormalities is not consist ent with the results of studies that found lower FA in pa tients with schizophrenia than BD 31,35 or those of studies that found no changes between these groups. 32,33,36 How ever, our finding is similar to that of a study comparing medicationnaive patients with firstepisode BD and schizo phrenia that reported lower FA in the callosal, subcortical and frontooccipital white matter regions in patients with BD.…”

“…26 The DTI studies directly comparing white matter between patients with schizophrenia and BD have so far yielded in consistent findings, with several studies showing no differ ences [31][32][33][34] and others finding distinct differences between the disorders. 15,35,36 The inconsistent findings could be explained by participant inhomogeneity. One study focused on first episode patients, 15 while others included patients with BDI with and without psychosis, 33,35 or did not specify whether the participants with BD had history of psychosis.…”

“…15,35,36 The inconsistent findings could be explained by participant inhomogeneity. One study focused on first episode patients, 15 while others included patients with BDI with and without psychosis, 33,35 or did not specify whether the participants with BD had history of psychosis. 36 The DTI methodologies among these studies vary too, including voxelbased analysis of all white matter voxels of the whole brain, 15,36 whole brain voxelbased approach followed by a priori regions of interest (ROI) analyses 31,32,33 and an ROI ap proach.…”

“…36 The DTI methodologies among these studies vary too, including voxelbased analysis of all white matter voxels of the whole brain, 15,36 whole brain voxelbased approach followed by a priori regions of interest (ROI) analyses 31,32,33 and an ROI ap proach. 35 A recent study -the only study to our knowledge that examined shared white matter abnormalities in patients with schizophrenia and BD 34 -adopted tractbased spatial statistics (TBSS), a wholebrain voxelbased approach focus ing on the major white matter tracts that are common and created from the cohort studied. 37 Hence in the present study, we sought to examine 3 hy potheses using complementary white matter diffusion meas ures in our cohort of patients with schizophrenia, patients with BD with a history of psychosis and healthy controls.…”

Abnormalities in brain white matter in adolescents with 22q11.2 deletion syndrome and psychotic symptoms

“…Reductions in all three dMRI indices, MD, AD and RD, have not been reported in patients with schizophrenia. Diffusivity increase is usually observed with increasing neurodegeneration, as reported in demyelinating diseases (Senda et al 2012; Della Nave et al 2004), but also in schizophrenia and bipolar disorder (Anderson et al 2013; Clemm von Hohenberg et al 2014). Reductions in MD, AD, and RD are usually observed in typically developing children and adolescents over the course of the first two decades of life (Lebel and Beaulieu 2011; Lebel et al 2012), which may suggest that changes in the dMRI measures observed here in 22q11DS might be a consequence of abnormal development, rather than the pathology observed in full blown psychosis.…”