Common gray and white matter abnormalities in schizophrenia and bipolar disorder

Abstract

This study aimed to investigate abnormalities in the gray matter and white matter (GM and WM, respectively) that are shared between schizophrenia (SZ) and bipolar disorder (BD). We used 3T-magnetic resonance imaging to examine patients with SZ, BD, or healthy control (HC) subjects (aged 20-50 years, N = 65 in each group). We generated modulated GM maps through voxel-based morphometry (VBM) for T1-weighted images and skeletonized fractional anisotropy, mean diffusion, and radial diffusivity maps through tract-based special statistics (TBSS) methods for diffusion tensor imaging (DTI) data. These data were analyzed using a generalized linear model with pairwise comparisons between groups with a family-wise error corrected P < 0.017. The VBM analysis revealed widespread decreases in GM volume in SZ compared to HC, but patients with BD showed GM volume deficits limited to the right thalamus and left insular lobe. The TBSS analysis showed alterations of DTI parameters in widespread WM tracts both in SZ and BD patients compared to HC. The two disorders had WM alterations in the corpus callosum, superior longitudinal fasciculus, internal capsule, external capsule, posterior thalamic radiation, and fornix. However, we observed no differences in GM volume or WM integrity between SZ and BD. The study results suggest that GM volume deficits in the thalamus and insular lobe along with widespread disruptions of WM integrity might be the common neural mechanisms underlying the pathologies of SZ and BD.

Insights into myelin dysfunction in schizophrenia and bipolar disorder

“…DTI studies of bipolar disorder have reported diffuse WM microstructural alterations[ 124 , 162 , 163 ], which are evident when tract integrity and WM volume are measured. Recent meta-analyses have found FA reductions in all major classes of WM tracts (commissural, association and projection fibers) with frequent reports of alterations in temporoparietal WM, the inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, and left cingulum[ 124 , 164 ].…”

Risk of retinal disease in patients with bipolar disorder: A nationwide cohort study

“…29 Indeed, previous structural, functional, and chemical imaging studies have reported neurodegeneration in the central nervous system of patients with BD. 4,5,30 Furthermore, the illness duration of BD correlated with the reduced thickness of the RNFL and GCL. 31,32 This was consistent with our finding that the BD group had a shorter duration from the time of enrollment to the diagnosis of a retinal disease than the control group.…”

“…Another study reported reduced thickness of RNFL and GCIPL in idiopathic retinal telangiectasia, a neurodegenerative retinal disease characterized by alterations in the macular capillary network, neurosensory atrophy, and occasional subretinal neovascularization 29 . Indeed, previous structural, functional, and chemical imaging studies have reported neurodegeneration in the central nervous system of patients with BD 4,5,30 . Furthermore, the illness duration of BD correlated with the reduced thickness of the RNFL and GCL 31,32 .…”

“…Various neuropathological findings of the brain have been associated with BD. 4,5 Previous structural neuroimaging studies have reported reduced gray matter and white matter volumes in patients with BD. Functional imaging studies have also identified abnormalities in the prefrontal and anterior cingulate cortices, as well as the amygdala and the ventral striatum.…”

Common and Specific Characteristics of Adolescent Bipolar Disorder Types I and II: A Combined Cortical Thickness and Structural Covariance Analysis

“…In our study, BD-II patients had a weaker SC connection between left PCG and left SFG vs. HCs. Studies regarding BD-I and BD-II as a whole found that FA in superior longitudinal fasciculus (SLF) was decreased in BD patients relative to HCs (70,71). SLF, as a major long association fiber tract, ipsilaterally connects parietal, frontal, temporal, and occipital cortices (67).…”