White matter microstructure in untreated first episode bipolar disorder with psychosis: comparison with schizophrenia

“…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.…”

“…[10][11][12] In patients with BD, neuroimaging evidence of preferential hemispheric abnormalities has been reported as well, although findings are not as conclusive; many converging studies of metabol ism, taskbased fMRI and white matter revealed preferential right hemispheric disturbances, whereas other studies found left hemispheric disturbances in patients with BD. [13][14][15][16][17][18] Clinically, the boundaries between schizophrenia and BD can be blurred early in the illness and even over time. 19,20 Given the overlap of psychotic symptomatology and risk gene loci, 21,22 direct comparisons of hemispheric lateralization in patients with schizophrenia and BD can yield insight into common and different pathophysiology underlying the shared and unique clinical features of these disorders.…”

“…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. 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.…”

“…27 Two other indices, axial diffusivity (AD) and radial diffusivity (AD), complement FA measures; they have been suggested to reflect axonal and myelin disruptions, respectively. 15,[28][29][30] An other widely used DTI index, mean diffusivity (MD), is used to quantify the average magnitude of diffusivity in a particular voxel or region in all directions. Increased MD may indicate axonal disruptions due to degeneration, myelin degeneration or edema (increase in tissue swelling).…”