Mean Fractional Anisotropy Values Research Articles

Characterization of Classic Meningioma with Use of Conventional Magnetic Resonance and Diffusion Tensor Imaging

Introduction: The conventional magnetic resonance imaging (MRI) method is widely considered ‘with limited success’ in differentiating the meningioma types but may fail to localize the tumor occupation of white-matter fiber bundles accurately. Diffusion tensor imaging (DTI) is considered as an imaging modality that may elucidate the microstructure of brain tumors. We provide characteristics of meningioma using DTI-based-three-dimensional tracing of white matter to portray meningioma in a noninvasive approach and its structural contact to contiguous tumors and elucidate the influence of occupying lesions on white-matter fiber bundles. Case Presentation: A 28-year-old female presented with visuospatial disturbances and persistent headaches for 2 years. Conventional and advanced MRI studies were performed. Diffusion-weighted Images (DWI) and Apparent Diffusion Coefficient (ADC) values were measured in the lesion using routine MRI sequences. Advanced MRI using DTI was also performed. Conventional MRI outcomes showed tumor parenchyma, peritumoral edema, and compression on the circumnavigated brain tissue. There was hyperintense on DW trace image and isointense on ADC map. On T2-weighted image (T2WI) and Fluid-Attenuated Inversion Recovery (FLAIR) images, there was an increased signal intensity that demonstrated an extra-axial lesion, while T1-weighted imaging signals showed hypointensity. DTI fractional anisotropy (FA) marker is an unclear optic radiation in the concerned area, indicating the shift or destruction of the optic radiation. The mean FA values of solid-enhancing areas of meningioma were 0.28 ± 0.17. Mean ADC values (103 mm2/s) were 0.764 ± 0.172. Conclusions: Classic meningioma in this case has low intratumoral FA and high ADC. DTI displayed that intratumoral microscopic water motion is disorganized.

Assessment of renal pathophysiological processes and protective effect of quercetin on contrast-induced acute kidney injury in type 1 diabetic mice using diffusion tensor imaging

ABSTRACT Purpose: To investigate the renal pathophysiological processes and protective effect of quercetin on contrast-induced acute kidney injury (CI–AKI) in mice with type 1 diabetic mellitus(DM) using diffusion tensor imaging(DTI). Methods: Mice with DM were divided into two groups. In the diabetic + contrast medium(DCA) group, the changes of the mice kidneys were monitored at 1, 24, 48, and 72 h after the injection of iodixanol(4gI/kg). The mice in the diabetic + contrast medium + quercetin(DCA + QE) group were orally given different concentrations of quercetin for seven days before injection of iodixanol. In vitro experiments, renal tubular epithelial (HK-2) cells exposed to high glucose conditions were treated with various quercetin concentrations before treatment with iodixanol(250 mgI/mL). Results: DTI-derived mean diffusivity(MD) and fractional anisotropy(FA) values can be used to evaluate CI-AKI effectively. Quercetin significantly increased the expression of Sirt 1 and reduced oxidative stress by increasing Nrf 2/HO-1/SOD1. The antiapoptotic effect of quercetin on CI-AKI was revealed by decreasing proteins level and by reducing the number of apoptosis-positive cells. In addition, flow cytometry indicated quercetin-mediated inhibition of M1 macrophage polarization in the CI-AKI. Conclusions: DTI will be an effective noninvasive tool in diagnosing CI-AKI. Quercetin attenuates CI-AKI on the basis of DM through anti-oxidative stress, apoptosis, and inflammation.

Subcortical white matter differences according to presence of disorders of consciousness in hypoxic-ischemic brain injury: a tract-based spatial statistics study.

We investigated differences in subcortical white matter according to the presence disorders of consciousness (DOC) in patients with hypoxic-ischemic brain injury (HI-BI), using tract-based spatial statistics (TBSS). Thirty-two consecutive patients with HI-BI were recruited. The patients were assigned in group A [preserved consciousness (Glasgow Coma Scale: 15 and Coma Recovery Scale-revised (CRS-R): 23, 9 patients)] or group B [DOC present (Glasgow Coma Scale <15 and CRS-R < 23, 20 patients)]. Voxel-wise statistical analysis of fractional anisotropy data was performed by using TBSS as implemented in the FMRIB Software Library. We calculated mean fractional anisotropy values across the white matter skeleton and within 48 regions of interest (ROIs) based on intersections between the skeleton and the probabilistic Johns Hopkins University white matter atlases. Among the 48 ROIs examined, the fractional anisotropy values of two ROIs (the left superior corona radiata, and left tapetum) were significantly lower in group B than in group A (P < 0.05). No significant differences were observed, however, in the other 46 ROIs (P > 0.05). Our results suggest that abnormalities of the superior corona radiata and tapetum may be critical for DOC presence in patients with HI-BI.

Presence of Auditory Pathway Abnormalities in Children With Neurofibromatosis Type 1 With Brainstem Focal Areas of Abnormal Signal Intensity: Diffusion Tensor Imaging Features.

Background: To investigate whether there is a difference in mean diffusivity (MD) and fractional anisotropy (FA) values in the auditory pathways of neurofibromatosis type 1 patients with and without focal areas of abnormal signal intensity (FASI) compared to healthy controls by using diffusion tensor imaging (DTI). Methods: Patients were classified as group 1 with focal areas of abnormal signal intensity in the brainstem, group 2 without focal areas of abnormal signal intensity, and healthy control group 3 according to the MRI findings. Mean diffusivity and fractional anisotropy values of lateral lemniscus, inferior colliculus, corpus geniculatum mediale, Heschl gyrus, and brainstem were compared between groups. The correlation between mean diffusivity and fractional anisotropy values of auditory pathways and age was investigated. Results: There was a significant difference between group 1 and group 2 in terms of mean diffusivity and fractional anisotropy values at lateral lemniscus, inferior colliculus, corpus geniculatum mediale, and Heschl gyrus. Increased mean diffusivity and decreased fractional anisotropy values at brainstem were found in group 1. There was a significant difference between group 1 and group 3 in terms of mean diffusivity values at all auditory pathways. Fractional anisotropy values obtained from lateral lemniscus, inferior colliculus, and Heschl gyrus decreased in group 1 compared with group 3. There was a negative correlation between mean diffusivity values and positive correlation between fractional anisotropy values at lateral lemniscus, inferior colliculus, Heschl gyrus, and age. Conclusions: Our diffusion tensor imaging findings show that the neuronal integrity of the auditory pathways is affected in neurofibromatosis type 1 patients with brainstem focal areas of abnormal signal intensity. We think that the disappearance of brainstem focal areas of abnormal signal intensity associated with myelin repair and the regression of diffusion tensor imaging changes in the auditory pathways occur simultaneously with advancing age in patients with neurofibromatosis type 1.

An anatomo-functional study of the interactivity between the paracentral lobule and the primary motor cortex.

The purpose of this study was to understand the anatomical and functional connections between the paracentral lobule (PCL) and the primary motor cortex (M1) of the human brain. This retrospective study included 16 patients who underwent resection of lesions located near M1. Nine patients had lesions in the dominant hemisphere. Tractography was performed to visualize the connectivity between two regions of interest (ROIs)-the convexity and the interhemispheric fissure-that were shown by functional MRI to be activated during a finger tapping task. The number, mean length, and fractional anisotropy (FA) of the fibers between the ROIs were estimated. During surgery, subdural electrodes were placed on the brain surface, including the ROIs, using a navigation system. Cortico-cortical evoked potentials (CCEPs) were evoked by applying electrical stimuli to the hand region of M1 using electrodes placed on the convexity and were measured with electrodes placed on the interhemispheric fissure. To verify CCEP bidirectionality, electrical stimuli were applied to electrodes on the interhemispheric fissure that showed CCEP responses. Correlations of CCEP amplitudes and latencies with the number, mean length, and mean FA value obtained from tractography were determined. The correlations between these parameters and perioperative motor functions were also analyzed. Fibers of 14 patients were visualized by diffusion tensor imaging (DTI). Unidirectional CCEPs between the PCL and M1 were measurable in all 16 patients, and bidirectional CCEPs between them were measurable in 14 patients. There was no significant difference between the two directions in the maximum CCEP amplitude or latency (amplitude, p = 0.391; latency, p = 0.583). Neither the amplitude nor latency showed any apparent correlation with the number, mean length, or mean FA value of the fibers obtained from tractography. Pre- and postoperative motor function of the hands was not significantly correlated with CCEP amplitude or latency. The number and mean FA value of fibers obtained by DTI, as well as the maximum CCEP amplitude, varied between patients. This study demonstrated an anatomical connection and a bidirectional functional connection between the PCL, including the supplementary motor area, and M1 of the human brain. The observed variability between patients suggests possible motor function plasticity. These findings may serve as a foundation for further studies.

Differential tractography and whole brain connectometry in primary motor area gliomas resection: A feasibility study

ObjectiveEstablish the evolution of the connectome before and after resection of motor area glioma using a comparison of connectome maps and high-definition differential tractography (DifT). MethodsDifT was done using normalized quantitative anisotropy (NQA) with DSI Studio. The quantitative analysis involved obtaining mean NQA and fractional anisotropy (FA) values for the disrupted pathways tracing the corticospinal tract (CST), and white fiber network changes over time. ResultsWe described the baseline tractography, DifT, and white matter network changes from two patients who underwent resection of an oligodendroglioma (Case 1) and an IDH mutant astrocytoma, grade 4 (Case 2). Case 1. There was a slight decrease in the diffusion signal of the compromised CST in the immediate postop. The NQA and FA values increased at the 1-year follow-up (0.18 vs. 0.32 and 0.35 vs. 0.44, respectively). Case 2. There was an important decrease in the immediate postop, followed by an increase in the follow-up. In the 1-year follow-up, the patient presented with radiation necrosis and tumor recurrence, increasing NQA from 0.18 in the preop to 0.29. Fiber network analysis: whole-brain connectome comparison demonstrated no significant changes in the immediate postop. However, in the 1-year follow up there was a notorious reorganization of the fibers in both cases, showing the decreased density of connections. ConclusionsConnectome studies and DifT constitute new potential tools to predict early reorganization changes in a patient’s networks, showing the brain plasticity capacity, and helping to establish timelines for the progression of the tumor and treatment-induced changes.

Impacts of dioxin exposure on brain connectivity estimated by DTI analysis of MRI images in men residing in contaminated areas of Vietnam.

Effects of dioxin exposure on gray matter volume have been reported in previous studies, but a few studies reported effects of dioxin exposure on white matter structure. Therefore, this study was undertaken to investigate the impact of dioxin exposure on white matter microstructure in men living in the most severely dioxin-contaminated areas in Vietnam. In 2019 brain MRI scans from 28 men living near Bien Hoa airbase were obtained at Dong Nai General Hospital, Vietnam, on a 3 T scanner using a conventional diffusion tensor imaging sequence. Two exposure markers were indicated by perinatal exposure estimated by assessment of maternal residency in a dioxin-contaminated area during pregnancy and by measurement of blood dioxin levels. A general linear model was used to compare fractional anisotropy (FA) values in 11 white matter tracts in both hemispheres between groups with and without perinatal dioxin exposure and groups with high and low blood dioxin levels after adjusting for covariates. The adjusted mean FA value in the left cingulum hippocampal part (CGH) was significantly lower in the perinatal dioxin exposure group compared with the group without perinatal dioxin exposure. The high blood TCDD group showed significantly reduced FA values in the left and right CGH and right uncinate fasciculus (UNC). Moreover, the high blood TEQ-PCDDs group showed significantly lower FA values in the left and right CGH and the left UNC. There were no significant differences in FA values between the groups with high and low TEQ-PCDFs levels or between the groups with high and low TEQ-PCDD/Fs levels. It was concluded that dioxin exposure during the perinatal period and adulthood may alter the microstructure of white matter tracts in individuals with neurodevelopmental disorders.

190 Do Fractional Anisotropy and Apparent Diffusion Coefficient From Diffusion Tensor Imaging Correlate to Symptoms of Radiculopathy? A Case Series From BACPAC MRI

INTRODUCTION: Quantitative diffusion tensor imaging (DTI) parameters such as fractional anisotropy (FA) and apparent diffusion coefficient (ADC) are used to detect axonal pathology in nerve injuries. METHODS: Ganglia of the lumbar plexus nerves (L1-5) were input as seeds to track the nerve fibers using Constant Solid Angle reconstruction. Fiber tracts and values of FA and ADC were extracted along the lumbar plexus nerve profiles. Change in pain (VAS) and disability (ODI) after interlaminar epidural steroid injection at site of compression was compared to the changes in FA and ADC values. RESULTS: Five exams from three patients with bilateral L4-5 foraminal narrowing were included in this study. Two patients were imaged at two time points, three months apart. The average age of the cohort was 62.6 ± 5.3 years. Mean FA values were lowest at L3 (left: 0.32 ± 0.08; right: 0.35 ± 0.05) and L4 (left: 0.39 ± 0.06; right: 0.38 ± 0.03). Correspondingly, mean ADC values were highest at L3 (left: 0.0017 ± 0.0002; right: 0.0016 ± 0.0001) and L4 (left: 0.0.0013 ± 0.0001; right: 0.0015 ± 0.0002). For one patient, pain did not change in severity and ODI improved from severe to moderate disability after steroid injection: FA increased with no significant change in ADC. For another patient, pain increased from moderate to severe and ODI stayed the same after injection: FA decreased and ADC did not significantly change. CONCLUSIONS: The tractography generated from the segmentation model demonstrated lowest FA and highest ADC values corresponding to the level of compression. For patient outcomes, the FA values were observed to be more sensitive to changes in pain and disability compared to the ADC values.

Association of disruption of the right posterior arcuate fasciculus with spatial neglect.

Spatial neglect is a debilitating condition observed in patients with right-sided brain injuries in whom there is defective awareness of the contralesional space. Although classically considered a right parietal lobe deficit, there has been increasing interest in the specific white matter (WM) architecture subserving spatial neglect. Patients who have lesions associated with chronic disruptions in visuospatial networks are of significant relevance in elucidating the WM tracts associated with spatial attention. In this study, the authors used two independent analytical methods to examine the relationship between WM connectivity changes and spatial attention. Thirty patients with right-sided glioma underwent diffusion tensor imaging (DTI) tractography and neuropsychological testing prior to tumor resection. Spatial neglect was assessed using the Bells Test. Diffusion connectometry analysis was performed to calculate the probability of injury to 55 WM tracts. Next, quantitative DTI tractography was used to reconstruct 9 major WM tracts and obtain fractional anisotropy (FA) and streamline number values as indices of connectivity. Differences in connectivity were assessed between patients with neglect and controls. Of the WM tracts analyzed by diffusion connectometry, only the right posterior segment of the arcuate fasciculus (psAF) showed a higher probability of disconnection in patients with evidence of hemispatial neglect compared to tract reconstructions of previously published healthy controls (hemineglect: 42% ± 12.5%, vs control: 6.3% ± 4.8% [mean ± SEM]; p < 0.05). Of the WM tracts reconstructed by DTI tractography, only the right psAF demonstrated consistently lower indices of connectivity based on the mean streamline number (hemineglect: 550.35 ± 183.41, vs control: 1407.01 ± 319.93; p < 0.05) and FA value (hemineglect: 0.40 ± 0.013, vs control: 0.44 ± 0.0063; p < 0.05) in patients who demonstrated neglect compared to controls. The right long segment of the arcuate fasciculus, inferior frontooccipital fasciculus, and inferior longitudinal fasciculus also demonstrated a lower streamline number, but not a lower FA value, in patients with evidence of hemineglect. These findings suggest that parietotemporal networks mediated by the right psAF may play a critical role in visuospatial attention. This analysis may help to disentangle the organization of the visuospatial attention networks, predict deficits in patients with glioma, and optimize surgical planning.

Sleep disturbances, altered brain microstructure and chronic headache in youth.

Chronic headache (persistent or recurrent headache for 3-months or longer) is highly prevalent among youth. While sleep disturbances have been associated with headache, their inter-relationship with brain connectivity remains unknown. This observational study examined whether self-report and actigraphy measures of sleep were associated with alterations to white matter tracts (i.e., uncinate fasciculus and cingulum) in youth with chronic headache versus healthy controls. Thirty youth aged 10-18 years with chronic headache and thirty controls underwent an MRI. Diffusion tensor images were obtained and mean fractional anisotropy values of the cingulum and uncinate were extracted. One-week prior to their MRI, youth wore an actigraph to obtain sleep duration, wake after sleep onset and sleep efficiency measures. Moreover, they completed questionnaires regarding their sleep quality and pain symptomatology. Linear regression was applied to examine the relationships between sleep (self-report and actigraphy), fractional anisotropy, and number of headache days per month. Self-report and actigraphy measures of sleep did not differ between patients and controls. However, poorer self-reported sleep quality was associated with lower fractional anisotropy values in the left uncinate (P = 0.05). Lower left uncinate fractional anisotropy was related to increased headache frequency (P = 0.002) in youth with chronic headache. Therefore, alterations to connectivity may be associated with the relationship between altered perceptions of sleep and headache chronicity.

Clinical applicability of automated tractography for stroke rehabilitation: Z-score conversion of fractional anisotropy.

[Purpose] To expand the applicability of diffusion-tensor tractography fractional anisotropy for stroke rehabilitation, this study aimed to provide references for representative neural tracts from non-lesioned hemispheres. Therefore, we applied the assessment of neural integrity to representative stroke patients using Z-score conversion. [Participants and Methods] Fractional anisotropy values were assessed in neural tracts, including the corticospinal tract, inferior fronto-occipital fasciculus, uncinate fasciculus, and anterior thalamic radiation, of stroke patients receiving acute care. [Results] Data were collected from 60 patients for the non-lesioned right hemisphere and 68 patients for the non-lesioned left hemisphere. Mean fractional anisotropy values in the corticospinal tract and inferior fronto-occipital fasciculus were notably elevated, reaching approximately 0.6 and 0.5, respectively. The mean fractional anisotropy values for other neural tracts were approximately 0.4, and, the overall standard deviations were approximately 0.04. In two typical stroke patients assessed using Z-scores, the scores in the corticospinal tract corresponded to the severity of the hemiparesis. The scores in the anterior thalamic radiation and inferior fronto-occipital fasciculus were associated with more significant brain dysfunction, including inattention and aphasia. [Conclusion] In this study, the Z-score findings related to stroke symptoms align with those reported in the literature, indicating the appropriateness of the methodology used and its potential in future applications.

Diffusion tensor imaging in photosensitive and nonphotosensitive juvenile myoclonic epilepsy

Introduction/backgroundJuvenile myoclonic epilepsy (JME) syndrome is known to cause alterations in brain structure and white matter integrity. The study aimed to determine structural white matter changes in patients with JME and to reveal the differences between the photosensitive (PS) and nonphotosensitive (NPS) subgroups by diffusion tensor imaging (DTI) using the tract-based spatial statistics (TBSS) method. MethodsThis study included data from 16 PS, 15 NPS patients with JME, and 41 healthy participants. The mean fractional anisotropy (FA) values of these groups were calculated, and comparisons were made via the TBSS method over FA values in the whole-brain and 81 regions of interest (ROI) obtained from the John Hopkins University White Matter Atlas. ResultsIn the whole-brain TBSS analysis, no significant differences in FA values were observed in pairwise comparisons of JME patient group and subgroups with healthy controls (HCs) and in comparison between JME subgroups. In ROI-based TBSS analysis, an increase in FA values of right anterior corona radiata and left corticospinal pathways was found in JME patient group compared with HC group. When comparing JME-PS patients with HCs, an FA increase was observed in the bilateral anterior corona radiata region, whereas when comparing JME-NPS patients with HCs, an FA increase was observed in bilateral corticospinal pathway. Moreover, in subgroup comparison, an increase in FA values was noted in corpus callosum genu region in JME-PS compared with JME-NPS. ConclusionsOur results support the disruption in thalamofrontal white matter integrity in JME, and subgroups and highlight the importance of using different analysis methods to show the underlying microstructural changes.

DTI changes of thalamic subregions in genetic frontotemporal dementia: findings from the GENFI cohort

AbstractBackgroundAtrophy of thalamic subregions has been observed across the spectrum of frontotemporal dementia (FTD). To gain better insight into underlying tissue changes, we investigated how thalamic subregional fractional anisotropy (FA) and mean diffusivity (MD) derived from diffusion tensor imaging (DTI) are altered in genetic FTD.MethodWe used our newly developed thalamus segmentation tool, which jointly combines structural and diffusion input MRI data, to segment thalami and extract thalamic subregional FA and MD values for 163 genetic mutation carriers and 126 non‐carriers with suitable 3T MRI data from the GENetic FTD Initiative (GENFI). Mutation carriers were divided according to their genetic diagnosis and CDR®+NACC FTLD global scores into presymptomatic/prodromal (≤0.5: 41 C9orf72, 59 GRN, 34 MAPT) and symptomatic (≥1: 8 C9orf72, 11 GRN, 10 MAPT) groups. Mean FA and MD values for thalamic subregions were obtained using diffusion tensors interpolated in the log domain and weighted by segmentation posterior probabilities. Thalamic subregional FA and MD values for presymptomatic and symptomatic mutation carriers within each genetic group were compared with non‐carriers using analysis of covariance with bootstrapping, where age, scanner type, and sex were covariates. We corrected for multiple comparisons and calculated percentage changes in adjusted FA and MD mean values for mutation carriers relative to non‐carriers.ResultThe only significant change at the presymptomatic stage was found for C9orf72 expansion carriers, who showed FA reduction in the intralaminar subregion (5%) (Figure 1, Table 1). In symptomatic C9orf72 expansion carriers, FA was reduced in the laterodorsal (21%), lateral posterior (13%), anteroventral (13%) and intralaminar (11%) subregions. Symptomatic MAPT mutation carriers also showed FA reduction in the laterodorsal (15%) and anteroventral (11%) subregions. No significant FA reductions were found for GRN mutation carriers and no significant MD changes were observed for any group after correction for multiple comparisons.ConclusionWe detected FA reductions of thalamic subregions only for C9orf72 expansion carriers at the presymptomatic stage, and for C9orf72 and MAPT mutation carriers at the symptomatic stage. Combined with the lack of robust MD changes, our findings may warrant further assessment of thalamic microstructure with more advanced diffusion models.

Microstructural differences in migraine: A diffusion-tensor imaging study.

Diffusion-tensor imaging can be applied to describe the microstructural integrity of the whole brain. As findings about microstructural alterations in migraine are inconsistent, we aimed to replicate the most frequent results and assess a relationship between migraine parameters and changes in microstructure. Diffusion-weighted MRI data of 37 migraine patients and 40 controls were collected. Two indices of diffusion of water molecules, fractional anisotropy and mean diffusivity were used in a voxel-wise analysis. Group comparisons were carried out in SPM12 using age and sex as covariates. Statistically significant results survived family-wise error correction (pFWE < 0.05). Migraine intensity, frequency, and duration were self-reported and correlated with mean fractional anisotropy and mean diffusivity values across clusters. Migraine patients showed significantly lower fractional anisotropy in occipital regions, and significantly higher fractional anisotropy in thirteen clusters across the brain. Mean diffusivity of migraine patients was significantly decreased in the cerebellum and pons, but it was not increased in any area. Correlation between migraine duration and fractional anisotropy was significantly positive in the frontal cortex and significantly negative in the superior parietal lobule. We suggest that microstructural integrity of the migraine brain is impaired in visual areas and shows duration-related alterations in regions of the default mode network.

Tau pathology relates to regional microstructural alterations of cerebral white matter in older adults with diverse cognitive spectrum

AbstractBackgroundGrowing evidences suggest that degeneration of cerebral white matter (WM) occurs in Alzheimer’s disease (AD) independently of cerebrovascular risks or injury. Previous studies using diffusion tensor imaging (DTI) have reported a loss of WM microstructural integrity in the corpus callosum (CC) and cingulum (CG) in AD dementia and mild cognitive impairment (MCI). However, only limited information is available for the relationship of in vivo AD‐specific pathologies including beta‐amyloid (Aβ) and tau accumulation with WM microstructal alterations. Thus, we aimed to examine the association between in vivo AD pathologies and microstructural integrity of the CC and CG through cross‐sectional and longitudinal approaches.MethodA total of 170 (74 cognitively normal, 58 MCI, and 38 AD dementia) older adults from the Korean Brain Aging Study for the Early diagnosis and prediction of Alzheimer’s disease cohort were included. All participants underwent comprehensive clinical assessment and multi‐modal brain imaging including [11C]‐Pittsburgh‐Compound‐B‐positron emission tomography (PET), 18F‐AV‐1451 PET, and DTI. The mean fractional anisotropy (FA) values were obtained for 2 regions of interests, the CC and CG on DTI. The data was analyzed using linear regression model adjusted for age, sex, APOE4 positivity, and vascular risk factor score. Regression‐based mediation analysis was also conducted to assess the mediation of tau for the relationship between Aβ and FA.ResultIn cross‐sectional analyses for baseline data, global tau deposition had a significant negative association with both CC and CG FA (β = ‐0.013, p = 0.004 and β = ‐0.011, p = 0.002), while global Aβ retention showed a negative association with only CG FA (β = ‐0.015, p = 0.004). Longitudinal analyses revealed that higher tau deposition at baseline was associated with both greater reduction of both CC and CG FA over 2 years (β = ‐0.010, p = 0.001 and β = ‐0.005, p = 0.046), whereas Aβ was associated with neither CC nor CG FA change over the period. Additional mediation analysis demonstrated that the cross‐sectional association between Aβ and CG FA was mediated by tau deposition, while there was no direct relationship between the two.ConclusionOur findings suggest that regional alterations of WM microstructural integrity in MCI and AD dementia, which occurs independently of vascular risks, are mainly related with tau pathology rather than amyloid pathology.

Aging of reward dopamine tracts in the human brain: A diffusion tensor imaging study.

The mesocortical tract (MCT) and mesolimbic tract (MLT) are reward dopaminergic tracts that have been shown to play a role in regulating reward stimuli, including both incentive salience and social stimuli. In the current study, we examined aging of the MCT and MLT in normal human participants to explain human brain structures using diffusion tensor tractography (DTT). Sixty-four healthy participants were recruited for this study and allocated to 3 groups based on participants' age. Diffusion tensor imaging was performed, and MCTs and MLTs were reconstructed using the probabilistic tractography method. A significant negative correlation was observed between age and fractional anisotropy and tract volume of the MCT and MLT, whereas a positive correlation was observed between age and mean diffusivity. The mean fractional anisotropy value of the MCT was significantly lower in the old group than in the young and middle-aged groups (P < .05). The mean diffusivity values of the MCT and MLT were significantly higher in the old group than in the young and middle-aged groups (P < .05). The mean tract volume values of the MCT and MLT were significantly lower in the old group than in the young group (P < .05). We found that degenerative changes in the MCT and MLT began in participants in the 20s-30s, progressed steadily throughout life, and accelerated in the 60s.

Brain white matter alterations in young adult male patients with childhood-onset growth hormone deficiency: a diffusion tensor imaging study.

This study aimed to detect white matter changes and different effects of thyroid hormone on the white matter integrity in young adult male patients with childhood-onset growth hormone deficiency (CO-GHD), compared with healthy people. Magnetic resonance imaging (structural imaging and diffusion tensor imaging) was performed in 17 young adult male patients with CO-GHD and 17 healthy male controls. The white matter volume, mean diffusivity (MD) values and fractional anisotropy (FA) values were quantified and compared between two groups (CO-GHD group vs. control group). We assessed the interaction effects between thyroid hormone and groups (CO-GHD group vs. control group) on white matter integrity. Patients with CO-GHD exhibited similar white matter volumes compared with controls. However, compared with the controls, patients with CO-GHD showed a significant reduction in FA values in six clusters and a substantial increase in MD values in four clusters, mainly involving the corticospinal tracts, corpus callosum and so on. Moreover, after correcting for insulin-like growth factor-1 levels, the significant interaction effects between groups (CO-GHD group vs. control group) and serum free thyroxine levels on MD values were noted in three clusters, mainly involving in superior longitudinal fasciculus and sagittal stratum. In conclusion, young males with CO-GHD showed white matter changes in multiple brain regions and different effects of thyroid hormone on the white matter integrity.

7 P-Tau and Education as Moderators of the Relation between APOE4 and Memory Performance in Older Adults with Varying Cognitive Status

Objective:White matter microstructure (WMM) potentially mediates the relation between APOE4 and memory performance. This study’s purpose was to understand whether p-tau effects this mediation model and whether education level differentially impacts the relations between these genetic and biological biomarkers’ influence on memory.Participants and Methods:Participants included 161 older adults (M=74 years, 40.4% female, 92% White, 74 e4 non-carriers, 87 e4 carriers) with subjective and objective cognitive impairment from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). A composite memory score created by ADNI was used as the outcome variable. Mean fractional anisotropy (FA) and radial diffusivity (RD) values of white matter tracts within regions of interest (i.e., fornix (FX), hippocampal cingulum (CGH)) were individually used as the measures of WMM. A moderated mediation was run to examine whether p-tau was a moderator of the mediation between APOE4, white matter microstructure, and memory. An exploratory dual moderated mediation analysis examined education as a moderator of the moderated mediation. Indirect effects were tested using bootstrapping procedures.Results:In the FA moderated mediation model, APOE4 was significantly related to FA of the fornix and memory performance. FA of the CGH and FX were also related to memory performance. With FA of the fornix as the mediator, the conditional indirect effect was not significant (95% CI[-.0009, .0070]). There was a trend suggesting at low (95% CI[-.2421, -.0140]) and average (95% CI[-.1658, -.0083]) levels of p-tau, FA of the fornix was a significant mediator but was non-significant at high levels of p-tau (95% CI [-.1322, .0341]). The RD moderated mediation model was non-significant. The FA and RD exploratory dual moderated mediation models were non-significant. However, the APOE4 x p-tau interaction with FA of the fornix as the mediator suggested a trend. At low levels of p-tau, increased education was related to a significant moderated mediation.Conclusions:Results suggest that FA of the fornix is a significant mediator between the relation of APOE4 and memory, and this may be dependent upon p-tau levels. When p-tau burden load was high, the path by which APOE4 impacts memory performance was not through white matter microstructure degradation. Additionally, the potential buffering effects of education may be most robust at lower levels of p-tau burden.

Effects of Damage to the Integrity of the Left Dual-Stream Frontotemporal Network Mediated by the Arcuate Fasciculus and Uncinate Fasciculus on Acute/Subacute Post-Stroke Aphasia.

(1) Background: To investigate the correlation between the integrity of the left dual-stream frontotemporal network mediated by the arcuate fasciculus (AF) and uncinate fasciculus (UF), and acute/subacute post-stroke aphasia (PSA). (2) Methods: Thirty-six patients were recruited and received both a language assessment and a diffusion tensor imaging (DTI) scan. Correlations between diffusion indices in the bilateral LSAF/UF and language performance assessment were analyzed with correlation analyses. Multiple linear regression analysis was also implemented to investigate the effects of the integrity of the left LSAF/UF on language performance. (3) Results: Correlation analyses showed that the diffusion indices, including mean fractional anisotropy (FA) values and the fiber number of the left LSAF rather than the left UF was significantly positively associated with language domain scores (p < 0.05). Multiple linear regression analysis revealed an independent and positive association between the mean FA value of the left LSAF and the percentage score of language subsets. In addition, no interaction effect of the integrity of the left LSAF and UF on language performance was found (p > 0.05). (4) Conclusions: The integrity of the left LSAF, but not the UF, might play important roles in supporting residual language ability in individuals with acute/subacute PSA; simultaneous disruption of the dual-stream frontotemporal network mediated by the left LSAF and UF would not result in more severe aphasia than damage to either pathway alone.

Diffusion tensor imaging in trigeminal neuralgia: beyond the normal morphology

BackgroundTrigeminal neuralgia (TN) is an electric-like recurrent pain of a sudden onset and is localized to the area supplied by the trigeminal nerve, and the patients are usually free in between the attacks. It’s one of the most common causes of facial pain and is commonly induced by mechanical irritation, and there’s strong evidence suggesting an insult at the trigeminal nerve root which is usually caused by a neurovascular compression. The aim of the study was to evaluate the role of diffusion tensor imaging (DTI) in the detection of microstructural changes of normal appearing trigeminal nerve in patients with trigeminal neuralgia and the correlation between DTI parameters and pain severity.ResultsThirty one cases were included in the study (16 patients with TN and 15 healthy controls) underwent MRI with diffusion tensor imaging. The fractional anisotropy (FA) values of the trigeminal nerves were recorded and then comparison between the affected and unaffected sides in TN patients and healthy controls was done, also the degree of FA reduction was correlated with the pain severity in TN groups. The mean FA value of the affected trigeminal nerves was 0.43 ± 0.083, while that of the unaffected sides was 0.56 ± 0.058. The mean FA value of the trigeminal nerves in the healthy controls was 0.54 ± 0.057. A significant statistical differences was found between affected and unaffected sides (P < 0.00001) and between the affected sides and healthy controls (P < 0.0003), while no statistically significant difference was detected between the unaffected side and the healthy controls. A strong negative correlation was found between the pain score and the degree of FA reduction (P < 0.001).ConclusionsDiffusion tensor imaging is a functional MRI technique which can detect the microstructural changes in the normal appearing trigeminal nerves in patients with trigeminal neuralgia with a strong negative correlation between the severity of pain and the degree of FA reduction of the affected trigeminal nerve.