Application of diffusion tensor imaging for detecting structural changes in the brain of schizophrenic patients

Abstract

Objective. Schizophrenia is a severe psychiatric illness. Although magnetic resonance imaging has been widely used for detecting brain structural and functional abnormalities in patients with schizophrenia, the findings are highly inconsistent between reports. This study investigates structural changes in the brains of schizophrenic patients. Methods. The brains of fifty male adults with schizophrenia and fifty age- and gender-matched healthy controls were scanned by diffusion tensor imaging. The differences in fractional anisotropy （FA） values between schizophrenic patients and healthy controls were analyzed. Results. Schizophrenic patients exhibited significantly decreased FA values in the right middle frontal gyrus, right inferior frontal gyrus, right superior temporal gyrus, left sub-temporal gyrus, left middle temporal gyrus, left cingulate gyrus, and left precentral gyrus compared with the control group. We did not find any brain regions with higher FA values in the patient group than in the control group. Conclusion. This study suggested that structural abnormalities in the frontal region of gray matter and white matter are present at the same time in patients with schizophrenia.     

Profiles of white matter tract pathology in frontotemporal dementia

Despite considerable interest in improving clinical and neurobiological characterisation of frontotemporal dementia and in defining the role of brain network disintegration in its pathogenesis, information about white matter pathway alterations in frontotemporal dementia remains limited. Here we investigated white matter tract damage using an unbiased, template‐based diffusion tensor imaging (DTI) protocol in a cohort of 27 patients with the behavioral variant of frontotemporal dementia (bvFTD) representing both major genetic and sporadic forms, in relation both to healthy individuals and to patients with Alzheimer's disease. Widespread white matter tract pathology was identified in the bvFTD group compared with both healthy controls and Alzheimer's disease group, with prominent involvement of uncinate fasciculus, cingulum bundle and corpus callosum. Relatively discrete and distinctive white matter profiles were associated with genetic subgroups of bvFTD associated with MAPT and C9ORF72 mutations. Comparing diffusivity metrics, optimal overall separation of the bvFTD group from the healthy control group was signalled using radial diffusivity, whereas optimal overall separation of the bvFTD group from the Alzheimer's disease group was signalled using fractional anisotropy. Comparing white matter changes with regional grey matter atrophy (delineated using voxel based morphometry) in the bvFTD cohort revealed co‐localisation between modalities particularly in the anterior temporal lobe, however white matter changes extended widely beyond the zones of grey matter atrophy. Our findings demonstrate a distributed signature of white matter alterations that is likely to be core to the pathophysiology of bvFTD and further suggest that this signature is modulated by underlying molecular pathologies. Hum Brain Mapp 35:4163–4179, 2014. © 2014 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.     

Changes in white matter microstructure related to non-linguistic cognitive impairment in post-stroke aphasia

ABSTRACT

Objects

Post-stroke aphasia (PSA) often have non-linguistic cognitive impairment. We aimed to ascertain its characteristics of non-linguistic cognitive impairment and the corresponding changes in white matter microstructures.     

Construction of a stereotaxic DTI atlas with full diffusion tensor information for studying white matter maturation from childhood to adolescence using tractography‐based segmentations

Reconstruction of white matter (WM) fiber tracts based on diffusion tensor imaging (DTI) is increasingly being used in clinical and research settings to study normal and pathological WM tissue as well as the maturation of this WM tissue. Such fiber tracking (FT) methodology, however, is highly dependent on the manual delineation of anatomical landmarks and the algorithm settings, often rendering the reproducibility and reliability questionable. Predefining these regions of interest on a fractional anisotropy (FA) atlas in standard space has already been shown to improve the reliability of FT results. In this paper, we constructed a new DTI atlas, which contains the complete diffusion tensor information in ICBM152 coordinates. From this high‐dimensional DTI atlas, and using robust FT protocols, we reconstructed a large number of WM tracts. Subsequently, we created tract masks from these fiber tract bundles and evaluated the atlas framework by comparing the reproducibility of the results obtained from our standardized tract masks with regions‐of‐interest labels from the conventional FA‐based WM atlas. Finally, we assessed laterality and age‐related WM changes in 42 normal subjects aged 0 to 18 years using these tractography‐derived tract segmentations. In agreement with previous literature, we observed an FA increase with age, which was mainly due to the decrease of perpendicular diffusivity. In addition, major functional pathways in the language, motor, and limbic system, showed a significant asymmetry in terms of the observed diffusion metrics. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.     

White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES: An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects. METHODS: Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum. RESULTS: Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls. CONCLUSIONS: Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.     

Frontal white matter microstructure, aggression, and impulsivity in men with schizophrenia: a preliminary study.

BACKGROUND: Aggression and impulsivity may involve altered frontal white matter. METHODS: Axial diffusion tensor images were acquired in 14 men with schizophrenia using a pulsed gradient, double spin echo, echo planar imaging method. White matter microstructural measures (fractional anisotropy and trace) were calculated from these data. Regions of interest were placed in frontal white matter on four slices. Impulsivity was measured using the Motor Impulsiveness factor of the Barratt Impulsiveness Scale. Aggressiveness was measured using the Assaultiveness scale of the Buss Durkee Hostility Inventory and the Aggression scale of the Life History of Aggression. RESULTS: Lower fractional anisotropy in right inferior frontal white matter was associated with higher motor impulsiveness. Higher trace in these regions was associated with aggressiveness. CONCLUSIONS: Inferior frontal white matter microstructure was associated with impulsivity and aggression in men with schizophrenia. These results implicate frontal lobe dysfunction in aggression and certain aspects of impulsivity.     

White matter structure in autism: preliminary evidence from diffusion tensor imaging.

BACKGROUND: Individuals with autism have severe difficulties in social communication and relationships. Prior studies have suggested that abnormal connections between brain regions important for social cognition may contribute to the social deficits seen in autism. METHODS: In this study, we used diffusion tensor imaging to investigate white matter structure in seven male children and adolescents with autism and nine age-, gender-, and IQ-matched control subjects. RESULTS: Reduced fractional anisotropy (FA) values were observed in white matter adjacent to the ventromedial prefrontal cortices and in the anterior cingulate gyri as well as in the temporoparietal junctions. Additional clusters of reduced FA values were seen adjacent to the superior temporal sulcus bilaterally, in the temporal lobes approaching the amygdala bilaterally, in occipitotemporal tracts, and in the corpus callosum. CONCLUSIONS: Disruption of white matter tracts between regions implicated in social functioning may contribute to impaired social cognition in autism.     

Impaired cerebrovascular hemodynamics are associated with cerebral white matter damage

White matter hyperintensities (WMH) in elderly individuals with vascular diseases are presumed to be due to ischemic small vessel diseases; however, their etiology is unknown. We examined the cross-sectional relationship between cerebrovascular hemodynamics and white matter structural integrity in elderly individuals with vascular risk factors. White matter hyperintensity volumes, fractional anisotropy (FA), and mean diffusivity (MD) were obtained from MRI in 48 subjects (75±7years). Pulsatility index (PI) and dynamic cerebral autoregulation (dCA) was assessed using transcranial Doppler ultrasound of the middle cerebral artery. Dynamic cerebral autoregulation was calculated from transfer function analysis (phase and gain) of spontaneous blood pressure and flow velocity oscillations in the low (LF, 0.03 to 0.15 Hz) and high (HF, 0.16 to 0.5 Hz) frequency ranges. Higher PI was associated with greater WMH (P<0.005). Higher phase across all frequency ranges was associated with greater FA and lower MD (P<0.005). Lower gain was associated with higher FA in the LF range (P=0.001). These relationships between phase and FA were significant in the territories limited to the middle cerebral artery as well as across the entire brain. Our results show a strong relationship between impaired cerebrovascular hemodynamics (PI and dCA) and loss of cerebral white matter structural integrity (WMH and DTI metrics) in elderly individuals.