Group Comparison Of Fractional Anisotropy Research Articles

Structural Connectivity Affecting Aspiration After Stroke.

Aspiration after stroke is associated with pneumonia and mortality. In this study, we investigated brain structural connectivity associated with aspiration after unilateral supratentorial stroke. Patients on oral feeding after stroke were divided into liquid aspiration (22 patients) and normal (18 patients) groups based on videofluoroscopic swallowing studies. Voxel-based lesion-symptom mapping and voxel-wise group comparison of fractional anisotropy, mode of anisotropy, and mean diffusivity maps were conducted. Voxel-based lesion-symptom mapping revealed no significant lesion differences between groups. The aspiration group showed significantly increased fractional anisotropy and mode of anisotropy in the anterior limb and the genu of the internal capsule in the right hemisphere. In contrast, the normal group showed significantly increased mean diffusivity, mainly in the superior longitudinal fasciculus in the right hemisphere (P < 0.05). Degeneration of the internal capsule in the right hemisphere was found to affect aspiration after stroke.

Relationship Between White Matter Microstructure and Hallucination Severity in the Early Stages of Psychosis: A Diffusion Tensor Imaging Study

Abstract Background Diffusion tensor imaging (DTI) studies have investigated the relationship between hallucinations in schizophrenia and white matter (WM) microstructure. However, only a few studies have focused on hallucination severity in the early stages of psychosis, and the involvement of the WM microstructure in the development of hallucinations remains unclear. This study aimed to examine the WM microstructure related to hallucination severity in the early stages of psychosis. Methods DTI analysis using tract-based spatial statistics (TBSS) was applied to 138 participants, consisting of 105 individuals with early stages of psychosis (56 individuals with clinical high risk for psychosis [CHR] and 49 individuals with first-episode psychosis [FEP]) and 33 healthy controls (HCs). Group comparisons of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were performed. We examined the association of FA, MD, RD, and AD with hallucination severity in the early stages of psychosis. Results Lower FA and higher MD and RD in multiple WM tracts were observed in the early stages of psychosis compared to HCs. We found an association between hallucination severity and increased MD in the WM tract, consisting mainly of the left superior longitudinal fasciculus (SLF) and inferior fronto-occipital fasciculus (IFOF). Conclusions Our findings indicate that dysconnectivity in brain networks associated with language processing is related to the development of hallucinations. Further studies of the early stages of psychosis are needed to elucidate the mechanism of hallucinations.

Localizing deficits in white matter tracts of patients with narcolepsy with cataplexy: tract-specific statistical analysis.

White matter alterations related to hypocretin pathway have been less evaluated in patients who have narcolepsy with cataplexy (NC), as compared to the identified exploration of gray matter and have varied among structural brain magnetic resonance imaging studies. The aim of this study was to investigate the disruption of specific white matter tracts in drug-naïve patients with NC, by using a tract-specific statistical analysis (TSSA). Forty drug-naïve NC patients with cataplexy and 42 heathy controls were enrolled in the study. All participants completed diffusion weighted imaging, polysomnography, and neuropsychological testing. At that time, we automatically identified fourteen major fiber tracts using diffusion tensor imaging techniques and analyzed the group comparison of fractional anisotropy (FA) values for each tract between the NC and controls, controlling for the participant's age and gender. The mean age of the NC patients was 26.9years and the onset age of daytime sleepiness and cataplexy was 16.7years and 19.9years, respectively. Relative to the controls, the NC patients showed that there were identified decreased FA values in the bilateral inferior fronto-occipital fasciculus (IFO). The Epworth sleepiness scale was positively correlated with FA values for the left IFO and right cingulate. The REM sleep latency was positively correlated with FA values for the left IFO, cingulate, and uncinate fasciculus in patients. This TSSA study revealed disintegration of the IFO in the NC patients and suggested that disintegration of WM tracts connected to the frontal cortex contributes to clinical manifestations of narcolepsy.

Diffusion imaging of mild traumatic brain injury in the impact accelerated rodent model: A pilot study

ABSTRACTPrimary Objective: There is a need to understand pathologic processes of the brain following mild traumatic brain injury (mTBI). Previous studies report axonal injury and oedema in the first week after injury in a rodent model. This study aims to investigate the processes occurring 1 week after injury at the time of regeneration and degeneration using diffusion tensor imaging (DTI) in the impact acceleration rat mTBI model.Research Design: Eighteen rats were subjected to impact acceleration injury, and three rats served as sham controls. Seven days post injury, DTI was acquired from fixed rat brains using a 7T scanner. Group comparison of Fractional Anisotropy (FA) values between traumatized and sham animals was performed using Tract-Based Spatial Statistics (TBSS), a method that we adapted for rats.Main Outcomes and Results: TBSS revealed white matter regions of the brain with increased FA values in the traumatized versus sham rats, localized mainly to the contrecoup region. Regions of increased FA included the pyramidal tract, the cerebral peduncle, the superior cerebellar peduncle and to a lesser extent the fibre tracts of the corpus callosum, the anterior commissure, the fimbria of the hippocampus, the fornix, the medial forebrain bundle and the optic chiasm.Conclusion: Seven days post injury, during the period of tissue reparation in the impact acceleration rat model of mTBI, microstructural changes to white matter can be detected using DTI.

Disruption of White Matter Integrity in Adult Survivors of Childhood Brain Tumors: Correlates with Long-Term Intellectual Outcomes.

BackgroundAlthough chemotherapy and radiation treatment have contributed to increased survivorship, treatment-induced brain injury has been a concern when examining long-term intellectual outcomes of survivors. Specifically, disruption of brain white matter integrity and its relationship to intellectual outcomes in adult survivors of childhood brain tumors needs to be better understood.MethodsFifty-four participants underwent diffusion tensor imaging in addition to structural MRI and an intelligence test (IQ). Voxel-wise group comparisons of fractional anisotropy calculated from DTI data were performed using Tract Based Spatial Statistics (TBSS) on 27 survivors (14 treated with radiation with and without chemotherapy and 13 treated without radiation treatment on average over 13 years since diagnosis) and 27 healthy comparison participants. Whole brain white matter fractional anisotropy (FA) differences were explored between each group. The relationships between IQ and FA in the regions where statistically lower FA values were found in survivors were examined, as well as the role of cumulative neurological factors.ResultsThe group of survivors treated with radiation with and without chemotherapy had lower IQ relative to the group of survivors without radiation treatment and the healthy comparison group. TBSS identified white matter regions with significantly different mean fractional anisotropy between the three different groups. A lower level of white matter integrity was found in the radiation with or without chemotherapy treated group compared to the group without radiation treatment and also the healthy control group. The group without radiation treatment had a lower mean FA relative to healthy controls. The white matter disruption of the radiation with or without chemotherapy treated survivors was positively correlated with IQ and cumulative neurological factors.ConclusionsLower long-term intellectual outcomes of childhood brain tumor survivors are associated with lower white matter integrity. Radiation and adjunct chemotherapy treatment may play a role in greater white matter disruption. The relationships between white matter integrity and IQ, as well as cumulative neurological risk factors exist in young adult survivors of childhood brain tumors.

E20 Diffusion Tensor Imaging In Huntington's Disease: Impact Of The Control For Corrupted Data In Comparisons At The Group Level

Background Corrupted gradient directions (GD) in diffusion weighted images may seriously affect reliability of diffusion tensor imaging (DTI)-based comparisons at the group level. In the present study a quality control (QC) algorithm 1 was employed to eliminate corrupted GD from DTI data. Effects of this procedure on comparisons between Huntington disease (HD) subjects and controls were assessed at the group level. Methods Sixty-one HD patients in early stages and forty matched healthy controls were studied in a longitudinal design (baseline and two follow-ups at three time points over 15 months), in a multicenter setting with standardised acquisition protocols on four different MR scanners at four European study sites 2 . QC was used to identify corrupted GD in DTI data sets. Differences in fractional anisotropy (FA) maps at the group level with and without elimination of corrupted GD were analysed. Results The elimination of corrupted GD had an impact on individual FA maps as well as on cross-sectional group comparisons between HD subjects and controls. Following application of the QC algorithm, a lower number of small clusters of FA changes were observed, compared with the analysis without QC-based elimination. However, the grosso modo pattern of regional reductions and increases in FA values was unchanged. Conclusion An impact on the result patterns of the comparison of FA maps between HD subjects and controls was observed depending on whether QC-based elimination of corrupted GD was performed. QC-based elimination of corrupted GD in DTI scans reduces the risk of type I and type II errors in cross-sectional group comparison of FA maps contributing to an increase in reliability and stability of group comparisons. Acknowledgment This work was supported by the European Union under the Seventh Framework programme – PADDINGTON Project, Grant Agreement No. 261358, and the European Huntington’s Disease Network (EHDN), project 070 – PADDINGTON. References Muller HP, et al . PLoS Curr 2011, RRN1232 Muller HP, et al . Neuroimage Clinical 2013,2:161–167

Tract-based spatial statistics of diffusion tensor imaging after corpus callosotomy in relation to seizure recurrence.

To delineate microstructural changes in transected white matter tracts after corpus callosotomy in relation to seizure recurrence using tract-based spatial statistics of diffusion tensor imaging (DTI-TBSS). We retrospectively included 12 total corpus callosotomy patients who had undergone serial pre- and postoperative DTI studies. The first postoperative DTI was performed within 6 months after callosotomy. The second postoperative DTI was performed in five patients with seizure recurrence (symptomatic group) and in seven patients without seizure recurrence (asymptomatic group) after 1 year following surgery. Group comparisons of fractional anisotropy (FA) with age- and sex-matched controls were performed in a whole brain voxel-wise manner using DTI-TBSS. The first postoperative DTI-TBSS showed a significant FA decrease in the entire corpus callosum in all patients. The second postoperative DTI-TBSS showed that a significant FA decrease remained in the entire corpus callosum in the asymptomatic group. However, in the symptomatic group, no significant decrease of FA was observed in some parts of the posterior body and splenium of the corpus callosum, although there was still a significant FA decrease in the genu of the corpus callosum. Using DTI-TBSS analysis, we characterized and visualized microstructural white matter changes over time in relation to seizure recurrence in callosotomy patients, suggesting that reorganization of some transected white matter tracts may be related to seizure recurrence. DTI-TBSS analysis can provide reliable and useful information about the state of white matter bundles affected by corpus callosotomy in a noninvasive manner.

White Matter Microstructure in Individuals at Clinical High Risk of Psychosis: A Whole-Brain Diffusion Tensor Imaging Study

The study of individuals at clinical high risk (CHR) for psychosis provides an important opportunity for unraveling pathological mechanisms underlying schizophrenia and related disorders. A small number of diffusion tensor magnetic resonance imaging (DTI) studies in CHR samples have yielded anatomically inconsistent results. The present study is the first to apply tract-based spatial statistics (TBSS) to perform a whole-brain DTI analysis in CHR subjects. A total of 28 individuals meeting CHR criteria and 34 healthy controls underwent DTI. TBSS was used for a group comparison of fractional anisotropy (FA), as well as axial, radial, and mean diffusivity (AD, RD, and MD). Conversion to psychosis was monitored during a mean follow-up period of 12.3 months. The rate of conversion to psychosis was relatively low (4%). TBSS revealed increased MD in several clusters in the right hemisphere, most notably in the superior longitudinal fasciculus (SLF), posterior corona radiata, and corpus callosum (splenium and body). Increased RD was restricted to a smaller area in the posterior parietal lobe. We present further evidence that white matter microstructure is abnormal in CHR individuals, even in a sample in which the vast majority do not transition to psychosis over the following year. In accord with previous studies on CHR individuals and patients with early-onset schizophrenia, our findings suggest an important pathological role for the parietal lobe and especially the SLF. The latter is known to undergo particularly dynamic microstructural changes during adolescence and early adulthood, a critical phase for the development of psychotic illness.

Thalamocortical Disconnection in the Orbitofrontal Region Associated With Cortical Thinning in Schizophrenia

Dysfunction of the thalamocortical pathway has been proposed as a putative underlying pathology of schizophrenia. Although the mechanisms involved remain unclear, postmortem studies suggest the involvement of altered neural projections from the thalamus to layers within the prefrontal cortex. To investigate thalamocortical connectivity in schizophrenia and to examine its possible association with cortical thinning in vivo. Case-control cross-sectional study. Department of Psychiatry at Kyoto University Hospital, Japan. A total of 37 patients with schizophrenia and 36 age-, sex-, and education-matched healthy controls recruited from the local community underwent diffusion-weighted imaging and T1-weighted 3-dimensional magnetic resonance imaging. Probabilistic tractography was performed to investigate thalamocortical pathways. Group differences in mean fractional anisotropy (FA) values were examined in the entire thalamocortical pathway, the thalamolateral prefrontal pathway, the thalamomedial prefrontal pathway, and the thalamo-orbitofrontal pathway. Surface-based analysis was performed to investigate cortical thickness, and the correlation between FA values and cortical thickness was examined. The patient group exhibited reduced FA values within the right thalamo-orbitofrontal pathway (P < .05 for the 8 group comparisons of FA, Bonferroni correction). In the patient group only, the mean FA value for this pathway was positively correlated with thickness of the right frontal polar and lateral orbitofrontal cortices (P < .05, clusterwise correction). These results suggest that, in schizophrenia, regional thalamocortical white matter pathology is specifically associated with cortical pathology in regions where fibers connect.

The structural correlates of functional deficits in early huntington's disease

Neuropathological studies in Huntington disease (HD) have demonstrated neuronal loss in the striatum, as well as in other brain regions including the cortex. With diffusion tensor MRI we evaluated the hypothesis that the clinical dysfunction in HD is related to regionally specific lesions of circuit-specific cortico-basal ganglia networks rather than to the striatum only. We included 27 HD and 24 controls from the TRACK-HD Paris cohort. The following assessments were used: self-paced tapping tasks, trail B making test (TMT), University of Pennsylvania smell identification test (UPSIT), and apathy scores from the problem behaviors assessment. Group comparisons of fractional anisotropy and mean diffusivity and correlations were performed using voxel-based analysis. In the cortex, HD patients showed significant correlations between: (i) self paced tapping and mean diffusivity in the parietal lobe at 1.8 Hz and prefrontal areas at 3 Hz, (ii) UPSIT and mean diffusivity in the parietal, and median temporal lobes, the cingulum and the insula, and fractional anisotropy in the insula and the external capsule, (iii) TMT B and mean diffusivity in the white matter of the superior frontal, orbital, temporal, superior parietal and post central areas, and (iv) apathy and fractional anisotropy in the white matter of the rectus gyrus. In the basal ganglia, we found correlations between the self paced tapping, UPSIT, TMT tests, and mean diffusivity in the anterior part of the putamen and the caudate nucleus. In conclusion, disruption of motor, associative and limbic cortico-striatal circuits differentially contribute to the clinical signs of the disease.

Effects of interpolation methods in spatial normalization of diffusion tensor imaging data on group comparison of fractional anisotropy

This study investigated the effects on the measurement of fractional anisotropy (FA) during interpolation of diffusion tensor images in spatial normalization, which is required for voxel-based statistics. Diffusion tensor imaging data were obtained from nine male patients with attention deficit/hyperactivity disorder and nine age-matched control subjects. Regions of interest were selected from the genu of corpus callosum (GCC) and the right anterior corona radiata (RACR), with FA values measured before and after spatial normalization using two interpolation algorithms: linear and rotationally linear. Computer simulations were performed to verify the experimental findings. Between-group difference in FA was observed in the GCC and RACR before spatial normalization (P<.00001). Interpolation reduced the measured FA values significantly (P<.00001 for both algorithms) but did not affect the group difference in the GCC. For the RACR, the between-group difference vanished (P=.968) after linear interpolation but was relatively unaffected by using rotationally linear interpolation (P=.00001). FA histogram analysis and computer simulations confirmed these findings. This work suggests that caution should be exercised in voxel-based group comparisons as spatial normalization may affect the FA value in nonnegligible degrees, particularly in brain areas with predominantly crossing fibers.