Vestibular symptoms, such as dizziness and balance impairment, are frequently reported following mild traumatic brain injury (mTBI) and are associated with a protracted recovery, yet the underlying ...neuroanatomical substrates remain unclear. The present study utilized advanced diffusion MRI (dMRI) techniques including both conventional diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to investigate microstructural white matter integrity in individuals with postconcussive vestibular dysfunction (PCVD) within the subacute injury period (median of 35 days from injury; IQR of 23). Study participants included 23 individuals with subacute PCVD and 37 healthy control subjects who underwent imaging and comprehensive clinical vestibular testing. Between-group voxelwise analysis of differences in white matter revealed areas of higher intra-neurite volume fraction (V
) and isotropic volume fraction (V
) within PCVD subjects compared to controls, which involved overlapping regions within the left hemisphere of the brain. Affected areas of higher V
and V
included the superior longitudinal fasciculus (SLF) and superior and posterior corona radiata (SCR and PCR, respectively). We examined the relationship between clinical vestibular measures and diffusion metrics including DTI (fractional anisotropy FA, mean diffusivity MD, radial diffusivity RD and axial diffusivity AD) and NODDI (intraneurite volume fraction V
, isotropic volume fraction V
, dispersion anisotropy DA, orientation dispersion index
ODI
) within 32 regions-of-interest. Clinical vestibular measures included self-reported measures, including the Dizziness Handicap Inventory, Visual Vertigo Analog Scale, and Vestibular/Ocular-Motor Screening, as well as objective vestibular testing using the sensory organization test. Significant correlations were found with clinical measures across all diffusion maps (except DA), within various regions of interest (ROIs), including SLF, SCR, and PCR. These results implicate several important association bundles that may potentiate sensory processing dysfunction related to PCVD. Whether these neuroanatomical differences found within the subacute phase of PCVD are in response to injury or represent preexisting structural variations that increase vulnerability to sensory processing dysfunction is unclear and remains an active area of study.
Given the prevalence of vestibular dysfunction in pediatric concussion, there is a need to better understand pathophysiological disruptions within vestibular and associated cognitive, affective, and ...sensory-integrative networks. Although current research leverages established intrinsic connectivity networks, these are nonspecific for vestibular function, suggesting that a pathologically guided approach is warranted. The purpose of this study was to evaluate the generalizability of the previously identified "vestibular neuromatrix" in adults with and without postconcussive vestibular dysfunction to young athletes aged 14-17.
This retrospective study leveraged resting-state functional MRI data from two sites. Site A included adults with diagnosed postconcussive vestibular impairment and healthy adult controls and Site B consisted of young athletes with preseason, postconcussion, and postseason time points (prospective longitudinal data). Adjacency matrices were generated from preprocessed resting-state data from each sample and assessed for overlap and network structure in MATLAB.
Analyses indicated the presence of a conserved "core" network of vestibular regions as well as areas subserving visual, spatial, and attentional processing. Other vestibular connections were also conserved across samples but were not linked to the "core" subnetwork by regions of interest included in this study.
Our results suggest that connections between central vestibular, visuospatial, and known intrinsic connectivity networks are conserved across adult and pediatric participants with and without concussion, evincing the significance of this expanded, vestibular-associated network. Our findings thus support this network as a workable model for investigation in future studies of dysfunction in young athlete populations.
The functional basis of cognitive and quality of life changes after liver transplant is unclear. We aimed to evaluate the neurometabolic and functional brain changes as modulators of cognition and ...quality of life after transplant in patients with cirrhosis who were with/without pretransplant cognitive impairment and hepatic encephalopathy (HE). Patients with cirrhosis underwent detailed cognitive and quality of life assessment at enrollment and 6 months after transplant. A subset underwent brain magnetic resonance imaging (functional magnetic resonance imaging fMRI, diffusion tensor imaging DTI, and magnetic resonance spectroscopy MRS) before and after transplant. Changes before and after transplant were analyzed in all patients and by dividing groups in those with/without pretransplant cognitive impairment or with/without pretransplant HE. MRS evaluated ammonia‐related metabolites; fMRI studied brain activation for correct lure inhibition on the inhibitory control test; and DTI studied white matter integrity. Sixty‐six patients (mean Model for End‐Stage Liver Disease score, 21.8; 38 HE patients and 24 cognitively impaired CI patients) were enrolled. Quality of life was significantly worse in CI and HE groups before transplant, which improved to a lesser extent in those with prior cognitive impairment. In the entire group after transplant, there was (1) significantly lower brain activation needed for lure inhibition (shown on fMRI); (2) reversal of pretransplant ammonia‐associated changes (shown on MRS); and (3) improved white matter integrity (shown on DTI). Importantly, study findings suggest that pretransplant cognitive impairment serves as a marker for clinical outcomes. Regardless of pretransplant history of HE, it was the pretransplant cognitive impairment that was predictive of both posttransplant cognitive and psychosocial outcomes. Therefore, when working with patients and their families, a clinician may rely on the pretransplant cognitive profile to develop expectations regarding posttransplant neurobehavioral recovery. We conclude that functional brain changes after liver transplant depend on pretransplant cognitive impairment and are ultimately linked with posttransplant cognition and quality of life in cirrhosis. Liver Transplantation 22 1379–1390 2016 AASLD.
Despite the associated adverse outcomes, pharmacologic intervention for covert hepatic encephalopathy (CHE) is not the standard of care. We hypothesized that a video game-based rehabilitation program ...would improve white matter integrity and brain connectivity in the visuospatial network on brain magnetic resonance imaging (MRI), resulting in improved cognitive function in CHE subjects on measures consistent with the cognitive skill set emphasized by the two video games (e.g., IQ Boost-visual working memory, and Aim and Fire Challenge-psychomotor speed), but also generalize to thinking skills beyond the focus of the cognitive training (Hopkins verbal learning test (HVLT)-verbal learning/memory) and improve their health-related quality of life (HRQOL). The trial included three phases over 8 weeks; during the learning phase (cognitive tests administered twice over 2 weeks without intervening intervention), training phase (daily video game training for 4 weeks), and post-training phase (testing 2 weeks after the video game training ended). Thirty CHE patients completed all visits with significant daily achievement on the video games. In a subset of 13 subjects that underwent brain MRI, there was a significant decrease in fractional anisotropy, and increased radial diffusivity (suggesting axonal sprouting or increased cross-fiber formation) involving similar brain regions (i.e., corpus callosum, internal capsule, and sections of the corticospinal tract) and improvement in the visuospatial resting-state connectivity corresponding to the video game training domains. No significant corresponding improvement in HRQOL or HVLT performance was noted, but cognitive performance did transiently improve on cognitive tests similar to the video games during training. Although multimodal brain imaging changes suggest reductions in tract edema and improved neural network connectivity, this trial of video game brain training did not improve the HRQOL or produce lasting improvement in cognitive function in patients with CHE.
Minimal hepatic encephalopathy (MHE) impairs daily functioning in cirrhosis, but its functional brain impact is not completely understood. To evaluate the effect of rifaximin, a gut-specific ...antibiotic, on the gut-liver-brain axis in MHE.
Hypothesis
: Rifaximin will reduce endotoxemia, enhance cognition, increase activation during working memory(N-back) and reduce activation needed for inhibitory control tasks.
Methods
: Cirrhotics with MHE underwent baseline endotoxin and cognitive testing, then underwent fMRI, diffusion tensor imaging and MR spectroscopy(MRS). On fMRI, two tasks; N-back (outcome: correct responses) and inhibitory control tests(outcomes: lure inhibition) were performed. All procedures were repeated after 8 weeks of rifaximin. Results were compared before/after rifaximin.
Results
: 20 MHE patients (59.7 years) were included; sixteen completed pre/post-rifaximin scanning with 92 % medication compliance. Pre-rifaximin patients had cognitive impairment. At trial-end, there was a significantly higher correct 2-back responses, ICT lure inhibitions and reduced endotoxemia(
p
= 0.002). This was accompanied by significantly higher activation from baseline in subcortical structures (thalamus, caudate, insula and hippocampus) and left parietal operculum (LPO) during N-back, decrease in fronto-parietal activation required for inhibiting lures, including LPO during ICT compared to baseline values. Connectivity studies in N-back showed significant shifts in linkages after therapy in fronto-parietal regions with a reduction in fractional anisotropy (FA) but not mean diffusivity (MD), and no change in MRS metabolites at the end of the trial. A significant improvement in cognition including working memory and inhibitory control, and fractional anisotropy without effect on MD or MRS, through modulation of fronto-parietal and subcortical activation and connectivity was seen after open-label rifaximin therapy in MHE.
Moral injury references emotional and spiritual/existential suffering that may emerge following psychological trauma. Despite being linked to adverse mental health outcomes, little is known about the ...neurophysiological mechanisms of this phenomenon. In this study, we examined neural correlates of moral injury exposure and distress using the Moral Injury Exposure and Symptom Scale for Civilians. We also examined potential moderation of these effects by race (Black vs. White individuals) given the likely intersection of race-related stress with moral injury.
Forty-eight adults ages 18 to 65 years (mean age = 30.56, SD = 11.93) completed the Moral Injury Exposure and Symptom Scale for Civilians and an affective attentional control measure, the affective Stroop task (AS), during functional magnetic resonance imaging; the AS includes presentation of threat-relevant and neutral distractor stimuli. Voxelwise functional connectivity of the bilateral amygdala was examined in response to threat-relevant versus neutral AS distractor trials.
Functional connectivity between the right amygdala and left postcentral gyrus/primary somatosensory cortex was positively correlated with the Moral Injury Exposure and Symptom Scale for Civilians exposure score (voxelwise p < .001, cluster false discovery rate-corrected p < .05) in response to threat versus neutral AS distractor trials. Follow-up analyses revealed significant effects of race; Black but not White participants demonstrated this significant pattern of amygdala-left somatosensory cortex connectivity.
Increased exposure to potentially morally injurious events may lead to emotion-somatosensory pathway disruptions during attention to threat-relevant stimuli. These effects may be most potent for individuals who have experienced multilayered exposure to morally injurious events, including racial trauma. Moral injury appears to have a distinct neurobiological signature that involves abnormalities in connectivity of emotion-somatosensory paths, which may be amplified by race-related stress.
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