Diffusion Metrics Research Articles

Comparison of four MRI diffusion models to differentiate benign from metastatic retropharyngeal lymph nodes

BackgroundConventional magnetic resonance diffusion-weighted imaging (DWI) and morphological features have limitations in distinguishing benign from metastatic retropharyngeal lymph nodes (RLNs). We aimed to compare the value of continuous-time random walk (CTRW), fractional-order calculus (FROC), stretched-exponential model (SEM), and conventional DWI, in combination with morphological features, for differentiating between the two groups.MethodsFifty-nine patients with 68 RLNs (23 benign and 45 metastatic) were enrolled. All patients underwent DWI with 12 b-values. Diffusion data were reconstructed using conventional DWI, SEM, FROC, and CTRW models, yielding nine parameters: apparent diffusion coefficient (ADC), distributed diffusion coefficient (DDC)SEM, αSEM, DFROC, βFROC, μFROC, DCTRW, αCTRW, and βCTRW. Diffusion parameters and morphological features were compared using Mann–Whitney U, independent sample t, or χ2 tests. Logistic regression analysis was performed to identify the best diffusion indicator for classification and to develop a multiparameter model combining morphological features. Area under the receiver operating curve (AUC) and DeLong tests were used.ResultsSignificant differences in diffusion parameters were found between benign and metastatic RLNs, except for αCTRW (p ≤ 0.022). Benign RLNs exhibited higher ADC, DDCSEM, DFROC, and DCTRW, while metastatic RLNs had higher αSEM, βFROC, μFROC, and βCTRW. Multivariate logistic regression analysis identified βCTRW as the optimal single diffusion indicator (AUC = 0.913). The combined model of βCTRW with morphological features further improved diagnostic performance and yielded an AUC of 0.948.ConclusionβCTRW is an effective noninvasive biomarker for distinguishing between benign and metastatic RLNs. Thus, combining βCTRW with morphological features enhances diagnostic efficiency.Relevance statementThis study demonstrates that βCTRW, derived from the continuous-time random walk diffusion model, when integrated with morphological features, offers a reliable, noninvasive diagnostic approach for differentiating between benign and metastatic retropharyngeal lymph nodes.Key PointsNon-Gaussian diffusion metrics outperformed conventional DWI.βCTRW was the best indicator for distinguishing benign from metastatic lymph nodes.Combining βCTRW with minimal axial diameter further improved diagnostic efficiency.Graphical

Decoupling of Neurochemical and White Matter Microstructural Integrity in Posterior Cingulate Cortex Predicts Early Alzheimer's Disease Progression.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by early metabolic and structural brain changes. These alterations are often detectable during mild cognitive impairment due to AD (AD-MCI), a prodromal stage of the disease. The posterior cingulate cortex (PCC), a critical brain region involved in memory and self-referential processing, is particularly vulnerable to these changes. We recruited 21 healthy controls (HC) and 20 AD-MCI patients to participate in this study. Point-Resolved Echo Spin Spectroscopy (PRESS) combined with MEGA-PRESS was employed to accurately measure levels of Gamma-Aminobutyric Acid (GABA) and Glx (Combination of Glutamate and Glutamine) in the PCC. Additionally, diffusion tensor imaging (DTI) was utilized to assess white matter (WM) microstructure integrity. Key metabolites, including N-acetylaspartate (NAA), choline (Cho), and myo-inositol (mI), were quantified to provide insights into neuronal health and metabolic status, while WM integrity was evaluated using fractional anisotropy (FA) and mean diffusivity (MD) metrics. In the PCC, AD-MCI patients exhibited a significant reduction in tNAA/tCr (1.22 ± 0.09 vs. HC 1.32 ± 0.07, p < 0.001) and NAA/mI (1.22 ± 0.12 vs. HC 1.44 ± 0.12, p < 0.001), along with an increase in mI/Cr (1.84 ± 0.28 vs. HC 1.60 ± 0.29, p = 0.012) and decreased GABA+/water (2.23 ± 0.78 vs. HC 2.98 ± 0.73, p = 0.003). Diffusion metrics revealed higher mean diffusivity in PCC-connected gray matter (GM_MD: 10.40 ± 0.79 vs. 9.53 ± 0.80 × 10⁻⁴ mm²/s, p < 0.01) and white matter (WM_MD: 0.09 ± 0.01 vs. 0.08 ± 0.01 × 10⁻² mm²/s, p < 0.01). Notably, in AD-MCI, NAA/mI was negatively correlated with WM_MD (r = - 0.462, p = 0.047), and tNAA/tCr was positively correlated with WM_FA (r = 0.580, p = 0.009). PCC neurochemical-microstructural decoupling (NAA/mI-MD dissociation with preserved tNAA/tCr-FA coupling) marks early AD progression. This dissociation pattern, reflecting concurrent neuronal dysfunction and compensatory glial responses, proposes a novel multimodal biomarker for tracking axonal degeneration prior to overt cognitive decline.

Microstructural differentiation of cerebral metastases, glioblastoma, meningioma and primary CNS lymphoma using advanced diffusion imaging techniques

Abstract Background Microstructural tumor characteristics discriminate metastases, glioblastoma, meningioma and primary CNS lymphoma. We aimed to assess these intracranial neoplasms utilizing multiparametric diffusion imaging as a translational measure of morphology. Methods We investigated 101 newly diagnosed intracranial tumors (35 metastases, 34 glioblastomas(GB), 21 meningiomas, 11 primary CNS lymphomas(PCNSL)) with advanced diffusion MRI including Diffusion Tensor Imaging (DTI), Neurite Orientation and Dispersion Imaging (NODDI), and Diffusion Microstructure Imaging (DMI). Beyond DTI-derived metrics (aD, FA, MD, rD), we extracted the NODDI and DMI intra-axonal (NODDI ICVF, DMI V-intra), extra-axonal cellular (DMI V-extra), and free water (NODDI ISO-VF, DMI V-CSF) fractions using a multi-compartment model. These metrics were read from contrast-enhancing tumor portions and compared across the entities Results Various microstructural parameters served as effective discriminators in pair-wise comparisons: ISO-VF demonstrated high accuracy in distinguishing metastases from PCNSL (accuracy 90.13%) and meningiomas (accuracy 80.69%). aD was most accurate in discriminating GB from PCNSL (accuracy 89.57%) and meningioma from PCNSL (accuracy 74.03%), similar to MD which distinguished GB from meningiomas (accuracy 77.73%). FA performed best in discriminating GB from metastases (accuracy 83.11%). Discrimination on two axes of directionality and compartmentalization illustrate the comprehensive approach of tumor assessment. Conclusion Advanced microstructural imaging facilitates discrimination of four common intracranial neoplasms. Features such as cell density, extent of free water, and directional cellular elements are reflected in the diffusion metrics to varying degrees. As part of a first non-invasive assessment, they may direct early diagnostic and therapeutic procedures.

Noise reduction in magnitude diffusion-weighted images using spatial similarity and diffusion redundancy.

Noise reduction in magnitude diffusion-weighted images using spatial similarity and diffusion redundancy.

Early life adversity and white matter microstructural organization-a systematic review.

Early life adversity, defined as exposure to stressful events during childhood, is a significant risk factor for the development of psychiatric disorders. Diffusion tensor imaging studies employing tract-based spatial statistics have shown microstructural abnormalities in white matter among individuals exposed to early life adversity; however, robust conclusions are yet to be drawn. This systematic review synthesizes findings of previous tract-based spatial statistics studies to identify the white matter alterations in adult brains exposed to early life adversity, in papers with methodological consistency. The literature search (April 2024) was conducted to identify tract-based spatial statistics studies that compared diffusion metrics between adults exposed to early life adversity and adults not. Embase, Pubmed, and PsycInfo were searched, retrieving 2458 articles. Following deduplication, 1739 titles and/or abstracts were screened. 1699 articles were excluded, and 40 full texts were reviewed. Seven articles, reporting on 764 subjects, met the inclusion criteria and were included in the narrative synthesis. Compared to controls, adults exposed to early life adversity showed lower fractional anisotropy values in white matter tracts of the limbic and visual processing systems, specifically the anterior thalamic radiation, inferior longitudinal fasciculus, corona radiata, uncinate fasciculus, inferior fronto-occipital fasciculus, and cingulum bundle. This systematic review highlights that early life adversity may underlie emotional dysregulation and contribute to an increased risk of psychopathology in later life and explores the potential neurobiological mechanisms that underpin these structural changes. Understanding these associations is crucial for developing targeted interventions aimed at mitigating the long-term impact of early life adversity.

The pattern and dynamics of white matter alterations in Spinocerebellar ataxia type 1: A diffusion-weighted magnetic resonance imaging study.

Spinocerebellar ataxia type 1 (SCA1) is a rare, neurodegenerative disease. Upcoming clinical disease-modifying trials require biomarkers sensitive to disease progression. This study aims to investigate diffusion MRI (dMRI) metrics as a possible outcome measure in such trials. 46 participants (26 SCA1, 20 matched healthy controls (HC)) underwent 3T MRI examination and clinical assessment of ataxia severity (SARA) at three timepoints over the duration of two years, including dMRI. Diffusion metrics (fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity) were examined using tract-based spatial statistics (TBSS) and ROI-based extraction. Results were evaluated for change over time and relation to disease severity. Cerebellar white matter, in particular all cerebellar peduncles, showed significant (p<0.001) differences between SCA1 and HC groups at baseline in all diffusion metrics. After two years, dynamics were only observed in the inferior cerebellar peduncle (ICP). However, a sub-group of early-stage disease patients (SARA ≤ 11) showed significant change in the corticospinal tract (CST) and pontine crossing tract (PCT), indicating stage-dependent dynamics. Cortical regions did not show cross-sectional differences between groups, but did change significantly in both anterior and posterior regions in the SCA1 group (p<0.001). SCA1 patients showed ignificantly impaired white matter integrity in the cerebellar regions, when compared to HC. At the group level, diffusion metrics show dynamic effects in the ICP and in cortical regions. Patients in early disease stages furthermore show dynamic change in the CST and PCT. This indicates that white matter alterations follow a specific pattern throughout the disease and that measurements thereof are most useful in clinical trials targeting early disease stages.

Experimentally induced colitis impacts myelin development and home-cage behavior in young pigs regardless of supplementation with oral gamma-cyclodextrin-encapsulated tributyrin.

Colitis, a chronic intestinal disorder that causes inflammation of the colonic mucosa, has been linked with structural brain abnormalities. To combat intestinal inflammation, researchers have investigated how nutritional supplementation, such as butyric acid, may ameliorate untoward effects. By encapsulating and using conjugates of butyrate, such as butyrate glycerides (i.e., tributyrin), slower release to the lower portions of the gastrointestinal tract can be achieved. Additionally, butyrate supplementation has been linked with supporting brain function and regulating integrity. In the present study, a total of 24 intact male pigs were artificially reared and randomly assigned to 1 of 3 treatment conditions: (1) a control milk replacer (CON), (2) control plus oral dextran sodium sulfate (DSS) to induce colitis, or (3) control supplemented with 9.0 mM of gamma-cyclodextrin encapsulated tributyrin (TBCD) plus oral DSS (TBCD+DSS). Pigs were orally administered DSS treatments daily from postnatal day (PND) 14-18. Continuous video recording began on PND 3 and ceased on PND 27 or 28, with videos processed and analyzed for home-cage tracking behavior. On PND 26 or 27, pigs underwent neuroimaging procedures to assess overall brain anatomy (MPRAGE), microstructure (DTI), and myelin (MWF). Home-cage spatial preference was not altered prior to DSS dosing or during the overall study period. However, TBCD+DSS pigs spent less (p < 0.05) time within quadrant 4 when compared with CON pigs. Across almost all 29 brain regions assessed, absolute volumes were observed to be smaller in the TBCD+DSS group compared with CON and DSS groups. However, once individual volumes were assessed relative to the whole brain, most treatment effects dissipated other than for gray matter volume (p = 0.041). Diffusivity was found to be altered in several regions across treatment groups, thereby indicating differences in fiber organization. In areas like the hippocampus and thalamus, when fractional anisotropy (FA) values were highest for a given treatment, in the other diffusion metrics (mean, radial, axial diffusivity) values were lowest for that same treatment, indicating more organized cellular structure. Several other diffusion trends and differences were observed across various regions. Lastly, myelin water fraction (MWF) values were lowest in DSS-treated groups compared with CON (p < 0.05) for the whole brain and left/right cortices. Overall, fiber organization and myelination were observed to be altered by experimentally induced colitis and contrary to expectations, tributyrin supplementation did not ameliorate these effects. Future work is warranted to investigate other protective nutritional mechanisms for colitis.

Connectivity related to major brain functions in Alzheimer disease progression: microstructural properties of the cingulum bundle and its subdivision using diffusion-weighted MRI

BackgroundThe cingulum bundle is a brain white matter fasciculus associated with the cingulate gyrus. It connects areas from the temporal to the frontal lobe. It is composed of fibers with different terminations, lengths, and structural properties, related to specific brain functions. We aimed to automatically reconstruct this fasciculus in patients with Alzheimer disease (AD) and mild cognitive impairment (MCI) and to assess whether trajectories have different microstructural properties in relation to dementia progression.MethodsMulti-shell high angular resolution diffusion imaging−HARDI image datasets from the "Alzheimer's Disease Neuroimaging Initiative"−ADNI repository of 10 AD, 18 MCI, and 21 cognitive normal (CN) subjects were used to reconstruct three subdivisions of the cingulum bundle, using a probabilistic approach, combined with measurements of diffusion tensor and neurite orientation dispersion and density imaging metrics in each subdivision.ResultsThe subdivisions exhibit different pathways, terminations, and structural characteristics. We found differences in almost all the diffusivity metrics among the subdivisions (p < 0.001 for all the metrics) and between AD versus CN and MCI versus CN subjects for mean diffusivity (p = 0.007–0.038), radial diffusivity (p = 0.008–0.049) and neurite dispersion index (p = 0.005–0.049).ConclusionResults from tractography analysis of the subdivisions of the cingulum bundle showed an association in the role of groups of fibers with their functions and the variance of their properties in relation to dementia progression.Relevance statementThe cingulum bundle is a complex tract with several pathways and terminations related to many cognitive functions. A probabilistic automatic approach is proposed to reconstruct its subdivisions, showing different microstructural properties and variations. A larger sample of patients is needed to confirm results and elucidate the role of diffusion parameters in characterizing alterations in brain function and progression to dementia.Key PointsThe microstructure of the cingulum bundle is related to brain cognitive functions.A probabilistic automatic approach is proposed to reconstruct the subdivisions of the cingulum bundle by diffusion-weighted images.The subdivisions showed different microstructural properties and variations in relation to the progression of dementia.Graphical

Tractography Analysis of White Matter Pathways Associated with Speech Impairment in Parkinson's Disease

Purpose: Parkinson’s disease (PD) is a progressive neurodegenerative disorder affecting multiple systems. Speech disorders, stemming from motor and nonmotor deficits, affect up to 89% of PD patients. This study examines the arcuate fasciculus (AF) and frontal aslant tract (FAT), white matter pathways linked to verbal fluency, which have not been previously assessed in PD. Methods: We included publicly available high-quality diffusion-weighted images (DWI) acquired with 120 gradient directions (b = 2500 s/mm²) from 27 PD patients (Age: 66 ± 8, 14 M, 13 F) and 26 age-, sex-, and education-matched controls (Age: 64 ± 8, 14 M, 12 F), processed using the Generalized Q-sampling Imaging (GQI) model (DSI Studio software) for white matter pathway reconstruction. The Automatic Fiber Tracking (AutoTrack) option in DSI Studio was used for virtual dissection of the AF and FAT. Diffusion metrics of mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), fractional anisotropy (FA), quantitative anisotropy (QA), and track volume measures were obtained and analyzed. Results: No significant correlation was observed between quantitative anisotropy and verbal fluency measures across PD and control groups. However, male PD patients exhibited reduced left FAT volume and significantly lower QA in bilateral FAT and left AF. Microstructural changes in the FAT were observed in male PD patients, but no correlation was found between verbal fluency scores and QA. Conclusion: Our results suggest a more severe impact on the microstructure of the FAT in male PD patients compared to females.

Left parietal structural connectivity mediates typical and atypical language laterality in temporal lobe epilepsy.

Subjects with left temporal lobe epilepsy may either show altered hemispheric language lateralization or retain typical, left lateralization. Examining the integrity of white matter pathways involved in the adaptation or maintenance of language lateralization in these patients could have important clinical implications for preserving or potentiating compensatory language mechanisms. We combined task functional magnetic resonance imaging and structural diffusion metrics to determine the dependency of lobe-based language laterality on white matter integrity in healthy participants and left temporal lobe epilepsy (TLE) patients. We tested for differences between individuals who expressed typical, left hemisphere laterality compared to those with atypical laterality patterns (bilateral or right hemisphere biased). A total of 41 left TLE patients and 51 sex- and age-matched healthy participants (HPs) were enrolled. In left temporal lobe epilepsy, typical patterns of frontal and temporal lateralities were less conditioned by the language-related white matter connections of the left temporal lobe. In typically organized epilepsy subjects, temporal lobe language laterality was dependent upon the structural connectivities of the left parietal lobe. Among atypically organized individuals, compared to HPs, TLE patients displayed frontal and parietal language lateralities mediated by the structural connectivities of the left parietal lobe. Language-related left parietal lobe connections were critical both for maintaining typical left hemisphere-biased language processing in the temporal lobe and for the formation of noncanonical, potentially adaptive language processing asymmetries in the frontal and parietal lobes. Assessments of the laterality and integrity of language skills in left temporal lobe epilepsy will require modeling white matter structural influences.

White matter microstructural alterations are associated with cognitive decline in benzodiazepine use disorders: a multi-shell diffusion magnetic resonance imaging study.

Benzodiazepine use disorders (BUDs) have become a public health issue that cannot be ignored. We aimed to demonstrate that patients with BUDs might undergo changes in white matter (WM) integrity, which are related to impaired cognitive function. We used diffusion tensor imaging (DTI), diffusion kurtosis imaging (DKI), neurite orientation dispersion and density imaging (NODDI), and mean apparent propagator (MAP) to observe changes in WM structure from 29 patients with sleep disorders with BUD (SDBUD), 33 patients with sleep disorders with non-BUD (SDNBUD), and 25 healthy participants. We also compared the diagnostic performance of the diffusion metrics and models in predicting the status of BUDs and evaluated the relationship between WM changes and cognitive impairment. BUD was closely associated with WM damage in the corpus callosum (CC) and pontine crossing tract (PCT). There were 14 main diffusion metrics that could be used to predict BUD status (P=0.001-0.023). DTI, DKI, NODDI, and MAP had similar satisfactory performance for predicting BUD status (P=0.001-0.021). Pearson correlation analysis showed a close relationship between the Trail Making Test B (TMT-B) and DTI/NODDI metrics in the splenium of the CC and PCT and between the Montreal Cognitive Assessment (MoCA) and MAP metrics in the splenium of the CC in the SDBUD group (P=0.008-0.040). Our findings provide evidence for the neurobiological mechanism of benzodiazepine addiction and a novel method for the clinical diagnosis of BUDs.

Denoising Improves Cross-Scanner and Cross-Protocol Test-Retest Reproducibility of Diffusion Tensor and Kurtosis Imaging.

The clinical translation of diffusion magnetic resonance imaging (dMRI)-derived quantitative contrasts hinges on robust reproducibility, minimizing both same-scanner and cross-scanner variability. As multi-site data sets, including multi-shell dMRI, expand in scope, enhancing reproducibility across variable MRI systems and MRI protocols becomes crucial. This study evaluates the reproducibility of diffusion kurtosis imaging (DKI)metrics (beyond conventional diffusion tensor imaging (DTI)), at the voxel and region-of-interest (ROI) levels on magnitude and complex-valued dMRI data, using denoising with and without harmonization. We compared same-scanner, cross-scanner, and cross-protocol variability for a multi-shell dMRI protocol (2-mm isotropic resolution, b = 0, 1000, 2000 s/mm2) in 20 subjects. We first evaluated the effectiveness of Marchenko-Pastur Principal Component Analysis (MPPCA) based denoising strategies for both magnitude and complex data to mitigate noise-induced bias and variance, to improve dMRI parametric maps and reproducibility. Next, we examined the impact of denoising under different population analysis approaches, specifically comparing voxel-wise versus region of interest (ROI)-based methods. We also evaluated the role of denoising when harmonizing dMRI across scanners and protocols. The results indicate that DTI and DKI maps visually improve after MPPCA denoising, with noticeably fewer outliers in kurtosis maps. Denoising, either using magnitude or complex dMRI, enhances voxel-wise reproducibility, with test-retest variability of kurtosis indices reduced from 15%-20% without denoising to 5%-10% after denoising. Complex dMRI denoising reduces the noise floor by up to 60%. Denoising not only reduced variability across scans and protocols, but also increased statistical power for low SNR voxel-wise comparisons when comparing cross sectional groups. In conclusion, MPPCA denoising, either over magnitude or complex dMRI data, enhances the reproducibility and precision of higher-order diffusion metrics across same-scanner, cross-scanner, and cross-protocol assessments. The enhancement in data quality and precision facilitates the broader application and acceptance of these advanced imaging techniques in both clinical practice and large-scale neuroimaging studies.

Thalamic microstructural alterations in cerebral small vessel disease with mild cognitive impairment: insights from diffusion kurtosis imaging.

This study aimed to investigate thalamic microstructural alterations in cerebral small vessel disease (CSVD) patients with mild cognitive impairment (MCI) using diffusion kurtosis imaging (DKI), and to examine the associations between DKI parameters and cognitive performance. The study included 80 CSVD patients and 40 healthy controls (HC). Based on Montreal Cognitive Assessment (MoCA) scores, CSVD patients were divided into MCI (n = 40) and non-MCI (n = 40) groups. DKI parameters of the thalamus and its subregions were compared among the three groups and correlated with cognitive performance. CSVD-MCI patients exhibited significant alterations in DKI parameters, predominantly in the left thalamus. Compared to HC, CSVD-MCI patients showed reduced FA and decreased kurtosis parameters (KFA, MK, AK), along with increased diffusivity metrics (MD, AD, RD). Subregional analysis revealed the most pronounced changes in the left posterior, medial, and ventral groups. The lateral geniculate nucleus showed particularly significant reductions in FA and KFA. Cognitive assessments revealed significant correlations between DKI parameters and cognitive performance, with BNT and VFT scores showing strong correlations with DKI parameters in the left thalamus, particularly in the posterior nucleus and pulvinar. Thalamic microstructural alterations may play a crucial role in cognitive decline among CSVD patients. Diffusion kurtosis imaging parameters may provide novel perspectives for investigating the mechanisms of cognitive deterioration in CSVD patients.

Microstructural alterations in superficial white matter associated with anhedonia and suicidal ideation in major depressive disorder.

Microstructural alterations in superficial white matter associated with anhedonia and suicidal ideation in major depressive disorder.

Structural and functional connectomics of the olfactory system in Parkinson's disease: a systematic review.

Structural and functional connectomics of the olfactory system in Parkinson's disease: a systematic review.

Construction of brain age models based on structural and white matter information.

Construction of brain age models based on structural and white matter information.

Characterizing the Effect of Repetitive Head Impact Exposure and mTBI on Adolescent Collision Sports Players' Brain with Diffusion Magnetic Resonance Imaging.

Athletes in collision sports frequently sustain repetitive head impacts (RHI), which, while not individually severe enough for a clinical mild traumatic brain injury (mTBI) diagnosis, can compromise neuronal organization by transferring mechanical energy to the brain. Although numerous studies target athletes with mTBI, there is a lack of longitudinal research on young collision sport participants, highlighting an unaddressed concern regarding cumulative RHI effects on brain microstructures. Therefore, this study aimed to investigate the microstructural changes in the brains' of high school rugby players due to repeated head impacts and to establish a correlation between clinical symptoms, cumulative effects of RHI exposure, and changes in the brain's microstructure. We conducted a longitudinal magnetic resonance imaging (MRI) study on 36 male high school rugby players across a season using 3D T1-weighted and multi-shell diffusion MRI sequences, comparing them with 20 matched controls. Players with concussions were separately tracked up to 6 weeks post-injury with three-times scans within this period. The Sport Concussion Assessment Tool (SCAT5) symptom scale assessed mTBI symptoms, and mouthguard-embedded kinematic sensors recorded head impacts. No significant volumetric changes in subcortical structures were found post-rugby season. However, there were substantial differences in mean diffusivity (MD) and axial diffusivity (AD) between the rugby players and controls across widespread brain regions. Diffusion metrics, especially AD, MD, and radial diffusivity of certain brain tracts, displayed strong correlations with SCAT5 symptom severity. Repeated head impacts during a rugby season may adversely affect the structural organization of the brain's white matter. The observed diffusion changes, closely tied to SCAT5 symptom burden, stress the profound effects of seasonal head impacts and highlight individual variability in response to repetitive head impact exposure. To better manage sports-related mTBI and guide return-to-play decisions, comprehensive studies on brain injury mechanisms and recovery post-mTBI/RHI exposure are required.

Quantifying neurodegeneration within subdivisions of core motor pathways in amyotrophic lateral sclerosis using diffusion MRI

BackgroundDiffusion MRI is sensitive to white matter changes in amyotrophic lateral sclerosis (ALS). The current study aimed to establish disease profiles across core motor pathways, and their relevance to clinical progression in ALS.MethodsSixty-five participants (ALS = 47; Control = 18) were recruited for the study. White matter integrity of motor, somatosensory, and premotor subdivisions within the corticospinal tract and corpus callosum were quantified by fibre density, fibre-bundle cross-section, structural connectivity, and fractional anisotropy. Analyses focused on identifying diffusion metrics and tract profiles sensitive to ALS pathology, and their association with clinical progression.ResultsReduced fibre density of the motor subdivision of the corpus callosum (CC) and corticospinal tract (CST) demonstrated best performance in classifying ALS from controls (area-under-curve: CCmotor = 0.81, CSTmotor = 0.76). Significant reductions in fibre density (CCmotor: p < 0.001; CSTmotor: p = 0.016), and structural connectivity (CCmotor: p = 0.008; CSTsomatosensory: p = 0.012) indicated presence of ALS pathology. Reduced fibre density & cross-section significantly correlated with severity of functional impairment (ALSFRS-R; CCmotor: r = 0.52, p = 0.019; CSTmotor: r = 0.59, p = 0.016). The largest effect sizes were generally found for motor and somatosensory subdivisions across both major white matter bundles.ConclusionCurrent findings suggest that ALS does not uniformly impact the corticospinal tract and corpus callosum. There is a preferential disease profile of neurodegeneration mainly impacting primary motor fibres. Microstructural white matter abnormality indicated presence of ALS pathology while macrostructural white matter abnormality was associated with severity of functional impairment. Quantification of white matter abnormality in corticospinal tract and callosal subdivisions holds translational potential as an imaging biomarker for neurodegeneration in ALS.

Functional connectivity and white matter microstructural alterations in patients with left basal ganglia acute ischemic stroke.

Lesions in the basal ganglia present different neuroimaging manifestations compared to other regions. The functional connectivity and white matter (WM) microstructural alterations in patients with left basal ganglia acute ischemic stroke (AIS) remain unknown. This study aimed to explore the alterations of functional connectivity and WM microstructure, as well as their relationship with cognitive performance in patients with left basal ganglia AIS. We acquired resting-state functional MRI (rs-fMRI) and diffusion kurtosis imaging (DKI) data from 41 individuals with left basal ganglia AIS and 41 healthy controls (HC). The degree centrality (DC) method was applied to calculate the functional connectivity and Tract-Based Spatial Statistics was employed to evaluate the voxel-based group differences of diffusion metrics for the values of fractional anisotropy (FA), mean diffusivity, axial diffusivity (AD), radial diffusivity, mean kurtosis (MK), axial kurtosis, and radial kurtosis (RK). AIS showed attenuated DC in the bilateral precuneus and enhanced DC in the left caudate nucleus, compared with HC. In AIS, DC in the left caudate nucleus correlated positively with the Montreal Cognitive Assessment (MoCA) score (r = 0.681, p < 0.05). AIS had significantly decreased FA, AD, MK, and RK in WM tracts, including the internal capsule (IC), genu of corpus callosum (CC), body of CC, left superior longitudinal fasciculus (SLF), left cerebral peduncle, left corticospinal tract, anterior corona radiata (ACR), and left cingulum gyrus (CG). The MK in a cluster including the body of CC, right IC, left cingulate, SLF, ACR, and left CG was also significantly negatively correlated with MoCA scores (r = -0.508, p < 0.05). This study revealed that left basal ganglia AIS not only disrupted the functional connectivity of the whole brain but also had a pervasive impact on the WM microstructure of the whole brain. These findings provide novel insights into the underlying neural mechanisms of early cognitive decline in patients after AIS.

Altered white matter microstructural integrity in patients with postherpetic neuralgia: a combined DTI and DTI-NODDI study.

Postherpetic neuralgia (PHN) is a debilitating condition resulting from herpes zoster infection, characterized by persistent pain that significantly impacts quality of life. This study aimed to investigate the white matter microstructural alterations associated with PHN and to assess the relationship between diffusion metrics and clinical symptoms. A total of 29 patients with PHN, 28 patients recovering from herpes zoster (RHZ), and 27 healthy controls (HC) were recruited, and clinical assessments were obtained to evaluate pain intensity and psychological distress. Diffusion tensor imaging (DTI) data was collected, followed by analysis of diffusion and neurite orientation dispersion and density imaging (NODDI) metrics. Statistical analyses included ANOVA to compare groups and Pearson correlation coefficients to assess relationships between imaging metrics and clinical outcomes. PHN patients exhibited significantly altered white matter integrity, specifically in neurite density index (NDI) and orientation dispersion index, compared to both RHZ patients and HC. Significant correlations were also found between altered imaging metrics and clinical assessments of pain and emotional distress, with lower fractional anisotropy (FA) and NDI associated with higher pain scores and psychological symptoms. Our study highlights significant microstructural changes in white matter tracts in patients with PHN, indicating compromised neural integrity that correlates with increased pain perception and emotional distress. NODDI demonstrated superior sensitivity in detecting these alterations compared to traditional DTI metrics, underscoring its potential for enhancing diagnostic and therapeutic approaches in managing chronic pain conditions like PHN.