Altered Brain Structure in Hemifacial Spasm Patients: A Multimodal Brain Structure Study.

Objective: Hemifacial spasm (HFS) is a clinical neurosurgical disease, which brain structural alterations caused by HFS remain a topic of debate. We evaluated changes in brain microstructure associated with HFS and observed their relevance to clinical characteristics. Methods: We enrolled 72 participants. T1-weighted structural and diffusion tensor images were collected from all participants using 3.0T magnetic resonance equipment. Voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) were used to identify changes in gray matter volume (GMV) and disruptions in white matter (WM) integrity. The severity of the spasms was graded using the Cohn scale. Results: VBM analysis revealed that the GMV was significantly reduced in the left Thalamus and increased GMV in the right Cerebellum IV-V of the HFS group. TBSS analysis showed that FA in the left superior longitudinal fasciculus (SLF) of the HFS group was significantly increased. GMV in the thalamus showed a negative correlation with disease duration and Cohn grade, while FA in the left SLF had a positive correlation with both the disease duration and Cohn grade. Conclusion: We identified regions with altered GMV in HFS patients. Additionally, we determined that FA in the left SLF might serve as a significant neural indicator of HFS.

Neuroanatomical profiles of cognitive phenotypes in patients with primary brain tumors.

Background: Patients with brain tumors demonstrate heterogeneous patterns of cognitive impairment, likely related to multifactorial etiologies and variable tumor-specific factors. Cognitive phenotyping offers a patient-centered approach to parsing heterogeneity by classifying individuals based on patterns of impairment. The aim of this study was to investigate the neuroanatomical patterns associated with each phenotype to gain a better understanding of the mechanisms underlying impairments. Methods: Patients with primary brain tumors were recruited for a prospective, observational study. Patients were cognitively phenotyped using latent profile analysis in a prior study, revealing 3 distinct groups: generalized, isolated verbal memory, and minimal impairment. Whole brain cortical thickness (CT), fractional anisotropy, and mean diffusivity (MD) were compared across phenotypes, and associations between imaging metrics and cognitive scores were explored. Results: Neurocognitive, structural MRI, and diffusion MRI data were available for 82 participants at baseline. Compared to the minimal impairment group, the generalized impairment group showed a widespread, bi-hemispheric pattern of decreased CT (P-value range: .004-.049), while the verbal memory impairment group showed decreased CT (P-value range: .006-.049) and increased MD (P-value range: .015-.045) bilaterally in the temporal lobes. In the verbal memory impairment group only, increased parahippocampal MD was associated with lower verbal memory scores (P-values < .01). Conclusions: Cognitive phenotypes in patients with brain tumors showed unique patterns of brain pathology, suggesting different underlying mechanisms of their impairment profiles. These distinct patterns highlight the biological relevance of our phenotyping approach and help to identify areas of structural and microstructural vulnerability that could inform treatment decisions.

Investigating the relationship between cognitive impairment and brain white matter tracts using diffusion tensor imaging in patients with prolactinoma.

BACKGROUND: Cognitive impairment is known to occur in patients with prolactinoma, but the underlying mechanism is unclear. OBJECTIVE: To evaluate cognitive function in patients with prolactinoma and to investigate the basis of possible cognitive impairment in brain white matter changes using diffusion tensor imaging (DTI). METHODS: 37 consecutive patients with prolactinoma and 37 healthy controls of similar age, sex, and education were enrolled in the study. Hormone levels were determined in all participants, comprehensive neuropsychological testing was performed, and DTI was used to reconstruct and evaluate white matter tracts. RESULTS: In patients with prolactinoma, short- and long-term visual and verbal memory, attention, concentration, and executive and language functions were impaired compared to the healthy group. When comparing the DTI results, lower fractional anisotropy (FA) values were found in the patients' right uncinate fasciculus (R-UF), indicating neuronal damage. After applying the Bonferroni correction, the two groups had no significant difference in 42 tracts (p > 0.0012 for all). A positive correlation was found between poor FA scores on the R-UF and low scores on long-term memory, category and letter fluency tests. In addition, patients with hypoprolactinemia had the worst short-term memory scores, while normoprolactinemia had the best scores. Also, the poorer R-UF FA values were found in the patients with hypoprolactinemia and the highest in those with normoprolactinemia. CONCLUSION: This study is the first to investigate reasons for cognitive dysfunction in patients with prolactinoma by DTI. No significant structural changes were found in brain tracts of patients with prolactinoma. Still, there may be a link between potential damage in the R-UF and cognitive dysfunction, and further research is needed. In addition, the results showed that the development of hypoprolactinemia is associated with cognitive dysfunction and emphasized that overtreatment should be avoided.

Predictive value of dynamic diffusion tensor imaging for surgical outcomes in patients with cervical spondylotic myelopathy.

BACKGROUND: Cervical spondylotic myelopathy (CSM) is the most common chronic spinal cord injury with poor surgical and neurologic recovery in the advanced stages of the disease. DTI parameters can serve as important biomarkers for CSM prognosis. The study aimed to investigate the predictive value of dynamic diffusion tensor imaging (DTI) for the postoperative outcomes of CSM. METHODS: One hundred and five patients with CSM who underwent surgery were included in this study. Patients were assessed using the Modified Japanese Orthopedic Association Score (mJOA) before and one year after surgery and then divided into groups with good (≥ 50%) and poor (< 50%) prognoses according to the rate of recovery. All patients underwent preoperative dynamic magnetic resonance imaging of the cervical spine, including T2WI and DTI in natural(N), extension (E), and flexion (F) positions. ROM, Cross-sectional area, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were measured at the narrowest level in three neck positions. Univariate and multivariate logistic regression were used to identify risk factors for poor postoperative recovery based on clinical characteristics, dynamic T2WI, and DTI parameters. Predictive models were developed for three different neck positions. RESULTS: Forty-four (41.9%) patients had a good postoperative prognosis, and 61 (58.1%) had a poor prognosis. Univariate analysis showed statistically significant differences in diabetes, number of compression segments, preoperative mJOA score, cross-sectional area ((Area-N), (Area-E), (Area-F)), ADC((ADC-N), (ADC-E), (ADC-F)) and FA (((FA-N), (FA-E), (FA-F)) (p < 0.05). Multivariable logistic regression showed that natural neck position: Area-N ([OR] 0.226; [CI] 0.069-0.732, p = 0.013),FA-N([OR]3.028;[CI]1.12-8.19,p = 0.029); extension ne-ck position: Area-E([OR]0.248;[CI]0.076-0.814,p = 0.021), FA-E([OR]4.793;[CI]1.737-13.228,p = 0.002);And flextion neck postion: Area-F([OR] 0.288; [CI] 0.095-0.87, p = 0.027),FA-F ([OR] 2.964; [CI] 1.126-7.801, p = 0.028) were independent risk factors for poor prognosis.The area under the curve (AUC) of the prediction models in the natural neck position, extension neck position, and flexion neck positions models were 0.708[(95% CI:0.608∼0.808), P < 0.001]; 0.738 [(95% CI:0.641∼0.835), P < 0.001]; 0.703 [(95% CI:0.602∼0.803), P < 0.001], respectively. CONCLUSION: Dynamic DTI can predict postoperative outcomes in CSM. Reduced FA in the extension position is a valid predictor of poor postoperative neurological recovery in patients with CSM.

White matter microstructure damage measured by automated fiber quantification correlates with pain symptoms in lung cancer patients.

To investigative the white matter (WM) alterations in lung cancer patients with cancer pain (CP+), and explore the correlations between damaged WM fiber tracts and clinical indicators. Twenty-six CP+, 26 lung cancer patients without CP (CP-), and 31 healthy controls (HC) were recruited. All participants underwent diffusion tensor imaging (DTI) and clinical assessments. Automated fiber quantification (AFQ) technique was performed to identify the 20 WM fiber bundles, and the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were extracted. Intergroup comparisons of these diffusion metrics were conducted based on the entire fiber bundle level and 100 node levels along each tract. The associations between altered diffusion metrics and the numeric rating scale (NRS) scores, as well as the pain duration, were analyzed. At the entire level, the CP + group showed impaired WM structure in the right cingulum hippocampus (CH_R). At the pointwise level, the CP + group exhibited extensive nodal FA reduction or MD, RD, and AD elevation. In addition, the AD of the posterior portion of the right inferior longitudinal fasciculus (ILF_R, nodes 71-75) in the CP + group was positively correlated with the pain duration, and the FA of CH_R (nodes 22-38) was negatively correlated with NRS score. Extensive WM microstructural damage may be a pattern of brain abnormalities in lung cancer patients with CP, and in particular, specific nodal disruption along pain-related fiber tracts may be a sensitive imaging biomarker to characterize the severity and duration of CP.

Utilizing diffusion tensor imaging as an image biomarker in exploring the therapeutic efficacy of forniceal deep brain stimulation in a mice model of Alzheimer's disease.

Objective.With prolonged life expectancy, the incidence of memory deficits, especially in Alzheimer's disease (AD), has increased. Although multiple treatments have been evaluated, no promising treatment has been found to date. Deep brain stimulation (DBS) of the fornix area was explored as a possible treatment because the fornix is intimately connected to memory-related areas that are vulnerable in AD; however, a proper imaging biomarker for assessing the therapeutic efficiency of forniceal DBS in AD has not been established.Approach.This study assessed the efficacy and safety of DBS by estimating the optimal intersection volume between the volume of tissue activated and the fornix. Utilizing a gold-electroplating process, the microelectrode's surface area on the neural probe was increased, enhancing charge transfer performance within potential water window limits. Bilateral fornix implantation was conducted in triple-transgenic AD mice (3 × Tg-AD) and wild-type mice (strain: B6129SF1/J), with forniceal DBS administered exclusively to 3 × Tg-AD mice in the DBS-on group. Behavioral tasks, diffusion tensor imaging (DTI), and immunohistochemistry (IHC) were performed in all mice to assess the therapeutic efficacy of forniceal DBS.Main results.The results illustrated that memory deficits and increased anxiety-like behavior in 3 × Tg-AD mice were rescued by forniceal DBS. Furthermore, forniceal DBS positively altered DTI indices, such as increasing fractional anisotropy (FA) and decreasing mean diffusivity (MD), together with reducing microglial cell and astrocyte counts, suggesting a potential causal relationship between revised FA/MD and reduced cell counts in the anterior cingulate cortex, hippocampus, fornix, amygdala, and entorhinal cortex of 3 × Tg-AD mice following forniceal DBS.Significance.The efficacy of forniceal DBS in AD can be indicated by alterations in DTI-based biomarkers reflecting the decreased activation of glial cells, suggesting reduced neural inflammation as evidenced by improvements in memory and anxiety-like behavior.

White matter microstructure and functional connectivity in the brains of infants with Turner syndrome.

Turner syndrome, caused by complete or partial loss of an X-chromosome, is often accompanied by specific cognitive challenges. Magnetic resonance imaging studies of adults and children with Turner syndrome suggest these deficits reflect differences in anatomical and functional connectivity. However, no imaging studies have explored connectivity in infants with Turner syndrome. Consequently, it is unclear when in development connectivity differences emerge. To address this gap, we compared functional connectivity and white matter microstructure of 1-year-old infants with Turner syndrome to typically developing 1-year-old boys and girls. We examined functional connectivity between the right precentral gyrus and five regions that show reduced volume in 1-year old infants with Turner syndrome compared to controls and found no differences. However, exploratory analyses suggested infants with Turner syndrome have altered connectivity between right supramarginal gyrus and left insula and right putamen. To assess anatomical connectivity, we examined diffusivity indices along the superior longitudinal fasciculus and found no differences. However, an exploratory analysis of 46 additional white matter tracts revealed significant group differences in nine tracts. Results suggest that the first year of life is a window in which interventions might prevent connectivity differences observed at later ages, and by extension, some of the cognitive challenges associated with Turner syndrome.

Radiomics based on diffusion tensor imaging and 3D T1-weighted MRI for essential tremor diagnosis.

Background: Due to the absence of biomarkers, the misdiagnosis of essential tremor (ET) with other tremor diseases and enhanced physiologic tremor is very common in practice. Combined radiomics based on diffusion tensor imaging (DTI) and three-dimensional T1-weighted imaging (3D-T1) with machine learning (ML) give a most promising way to identify essential tremor (ET) at the individual level and further reveal the potential imaging biomarkers. Methods: Radiomics features were extracted from 3D-T1 and DTI in 103 ET patients and 103 age-and sex-matched healthy controls (HCs). After data dimensionality reduction and feature selection, five classifiers, including the support vector machine (SVM), random forest (RF), logistic regression (LR), extreme gradient boosting (XGBoost) and multi-layer perceptron (MLP), were adopted to discriminate ET from HCs. The mean values of the area under the curve (mAUC) and accuracy were used to assess the model's performance. Furthermore, a correlation analysis was conducted between the most discriminative features and clinical tremor characteristics. Results: All classifiers achieved good classification performance (with mAUC at 0.987, 0.984, 0.984, 0.988 and 0.981 in the test set, respectively). The most powerful discriminative features mainly located in the cerebella-thalamo-cortical (CTC) and visual pathway. Furthermore, correlation analysis revealed that some radiomics features were significantly related to the clinical tremor characteristics in ET patients. Conclusion: These results demonstrated that combining radiomics with ML algorithms could not only achieve high classification accuracy for identifying ET but also help us to reveal the potential brain microstructure pathogenesis in ET patients.

Comparing the imaging characteristics of middle-aged patients with multiple sclerosis and CADASIL: A retrospective cross-sectional study.

BACKGROUND: Few studies have quantitatively analyzed the imaging disparities between multiple sclerosis (MS) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). We aimed to compare the imaging characteristics of MS and CADASIL in middle-aged patients. MATERIALS AND METHODS: This retrospective study used a single-center database and included patients aged 40-60 years with MS and CADASIL who underwent the designated imaging protocol including 3D T1-weighted imaging and fluid attenuated inversion recovery (FLAIR), diffusion tensor imaging and susceptibility-weighted imaging between January 2018 and March 2023. Patients with MRI-detected macrobleeds were excluded. RESULTS: A total of 27 patients with MS (mean age, 46.7 years ± 4.4, 8 men) and 30 patients with CADASIL (mean age, 51.6 years ± 5.8, 14 men) were included. No significant differences were observed in the Fazekas grades of white matter lesions (WMLs). Patients with CADASIL exhibited greater external capsule involvement (56.7% vs.18.5 %; p = 0.006), whereas the MS group had more lesions in the corpus callosum (81.5% vs. 53.3 %, p = 0.02) and brainstem (74.1% vs. 46.7 %, p = 0.04). The CADASIL group exhibited a higher incidence of microbleeds (12.07 vs. 0.11, p = 0.001). The WMLs in the MS group exhibited a lower T1 lesion/cerebrospinal fluid signal index (2.206 vs. 2.882, p < 0.001). A value of ≤2.57 demonstrated a sensitivity of 92.6 % and a specificity of 90.0 % in differentiating MS. Patients with MS had a thinner corpus callosum (7.18 mm vs 7.86 mm, p = 0.04), while patients with CADASIL showed significantly higher mean diffusivity (0.8776 × 10-3 vs. 0.7637 × 10-3 mm2/s, p = 0.03) and lower fractional anisotropy (0.7581 vs. 0.8389, p = 0.04) in the splenium of the corpus callosum. CONCLUSION: Middle-aged patients with MS and CADASIL showed comparable Fazekas grades for WMLs. However, lesion distribution, T1 signal characteristics, and splenic diffusivity changes can help differentiate between MS and CADASIL.

Diffusion tensor imaging biomarkers and clinical assessments in amyotrophic lateral sclerosis (ALS) patients: an exploratory study.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of upper and lower motor neurons. Biomarkers are needed to improve diagnosis, gauge progression, and evaluate treatment. Diffusion tensor imaging (DTI) is a promising biomarker for detecting microstructural alterations in the white matter tracts. This study aimed to assess DTI metrics as biomarkers and to examine their relationship with clinical assessments in patients with ALS. Eleven patients with ALS and 21 healthy controls (HCs) underwent 3T MRI with DTI. DTI metrics, including fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), were compared between key motor and extra-motor tract groups. Group comparisons and correlations between DTI metrics also correlated with clinical scores of disability (ALSFRS-R), muscle strength (dynamometry), and motor unit loss (MUNIX). Widespread differences were found between patients with ALS and HCs in DTI metrics, including decreased FA and increased diffusivity metrics. However, MD and RD are more sensitive metrics for detecting white matter changes in patients with ALS. Significant interhemispheric correlations between the tract DTI metrics were also observed. DTI metrics showed symmetry between the hemispheres and correlated with the clinical assessments. MD, RD, and AD increases significantly correlated with lower ALSFRS-R and MUNIX scores and weaker dynamometry results. DTI reveals microstructural damage along the motor and extra-motor regions in ALS patients. DTI metrics can serve as quantitative neuroimaging biomarkers for diagnosis, prognosis, monitoring of progression, and treatment. Combined analysis of imaging, electrodiagnostic, and functional biomarkers shows potential for characterizing disease pathophysiology and progression.

A comparative study of vestibular projection connectivity and balance in healthy young adults and elderly subjects.

OBJECTIVE: Vestibular function is controlled by interactions between various neuropathways that have different effects on balance and are connected to various brain areas. However, few studies have investigated the relation between changes in VN connectivity and aging using neuroimaging. We investigated neural connectivities in the vestibular nucleus (VN) and ventralis intermedius (VIM) nucleus of the thalamus in young and old healthy adults by diffusion tensor imaging. METHODS: This study recruited twenty-three normal healthy adults with no history of a neurological or musculoskeletal disease, that is, eleven old healthy adults (6 males, 5 females; mean age 63.36 ± 4.25 years) and 12 young healthy adults (7 males, 5 females; mean age 28.42 ± 4.40 years). Connectivity was defined as the incidence of connection between the VN, VIM, and target brain regions. Incidence of connection was counted from VN and VIM to each brain region. The subjective visual vertical (SVV) and the Berg balance scale (BBS) were used to assess vestibular function and balance. RESULTS: The VN showed high connectivity with brainstem (dentate nucleus, medial longitudinal fasciculus, and VIM), but relatively low connectivity with cerebral cortex (parieto-insular vestibular cortex (PIVC) and primary somatosensory cortex) at a threshold of 30 streamlines. In particular, VN connectivity with PIVC was significantly lower in elderly adults (> 60 years old) than in young adults (20-40 years old) (p < 0.05). VIM showed high to mid connectivity with brainstems and cerebral cortexes at a threshold of 30, but no significant difference was observed between young and old adults (p > 0.05). SVV and BBS showed no significant differences between young and old adults (p > 0.05). CONCLUSION: We investigated incidences of neural connectivities of VN and VIM in young and old healthy adults. Our results provide basic data that might be clinically useful following injury of vestibular-related areas.

Microstructural Changes in the Corpus Callosum in Neurodegenerative Diseases.

The corpus callosum, the largest white matter structure in the brain, plays a crucial role in interhemispheric communication and cognitive function. This review examines the microstructural changes observed in the corpus callosum across various neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS). New neuroimaging studies, mainly those that use diffusion tensor imaging (DTI) and advanced tractography methods, were put together to show how changes have happened in the organization of white matter and the connections between them. Some of the most common ways the corpus callosum breaks down are discussed, including less fractional anisotropy, higher mean diffusivity, and atrophy in certain regions. The relationship between these microstructural changes and cognitive decline, motor dysfunction, and disease progression is explored. Additionally, we consider the potential of corpus callosum imaging as a biomarker for early disease detection and monitoring. Studies show that people with these disorders have lower fractional anisotropy and higher mean diffusivity in the corpus callosum, often in ways that are specific to the disease. These changes often happen before gray matter atrophy and are linked to symptoms, which suggests that the corpus callosum could be used as an early sign of neurodegeneration. The review also highlights the implications of these findings for understanding disease mechanisms and developing therapeutic strategies. Future directions, including the application of advanced imaging techniques and longitudinal studies, are discussed to elucidate the role of corpus callosum degeneration in neurodegenerative processes. This review underscores the importance of the corpus callosum in understanding the pathophysiology of neurodegenerative diseases and its potential as a target for therapeutic interventions.

In vivo cardiac diffusion tensor imaging on an MR system featuring ultrahigh performance gradients with 200 mT/m maximum gradient strength.

PURPOSE: Our aim is to assess the potential of an MR system with ultrahigh performance gradients (200 mT/m maximum gradient strength) to address two interrelated challenges in cardiac DTI: low SNR and sensitivity to bulk motion. METHODS: Imaging was performed in 20 healthy volunteers, two patients, and one swine post-myocardial infarction. The impact of maximum gradient strength was assessed with spin echo cardiac DTI featuring second-order motion compensation and varying maximum system gradient strengths (40, 80, 200 mT/m). Motion compensation requirements at 200 mT/m were assessed with sequences featuring zeroth-, first-, and second-order motion compensation. SNR, mean diffusivity, fractional anisotropy, helix angle transmurality, and secondary eigenvector angle in the left ventricle were compared. RESULTS: Increasing maximum system gradient strength from 40 and 80 mT/m to 200 mT/m increased SNR of b = 500 s/mm2 images by 150% and 40% due to reductions in TE. Observed improvements in DTI metrics included reduction in variance in mean diffusivity and helix angle transmurality across healthy volunteers, improved visualization of myocardial borders and delineation of suspected scar. Whereas second-order motion compensation acquisitions were robust to motion-induced signal dropout, zeroth- and first-order motion compensation acquisitions suffered from severe signal loss and localized signal voids, respectively. CONCLUSION: Ultrahigh performance gradients (200 mT/m) enable high SNR DWIs of the heart and resultant improvements in diffusion tensor metrics. Despite reduced diffusion-encoding duration, second-order motion compensation is required to overcome sensitivity to cardiac motion.

Diffusion Tensor Imaging of Rat Rotator Cuff Muscle with Histopathological Correlation: An Exploratory Study.

Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that can be used to assess microstructural features of skeletal muscle that are related to tissue function. Although widely used, direct correlations between DTI derived metrics such as fractional anisotropy and spatially matched tissue microstructure assessed with histology have not been performed. This study investigated the relationship between scalar-based DTI measurements and histologically derived muscle microstructural measurements in rat rotator cuff muscles. Despite meticulous co-localization of MRI and histology data, negligible correlations were found between DTI metrics and histological measurements including muscle fiber diameter, cross-sectional area, and surface-to-volume ratio. These findings highlight the challenges in validating DTI with histology due to requirements in anatomical co-localization, necessity of high-quality histology, and consideration of diffusion measurement scales. Our findings underscore the need for further research with optimized imaging parameters to enhance our knowledge regarding the sensitivity of DTI to important features of muscle microstructure.

Increased extracellular free water is related to white matter hyperintensity burden.

BACKGROUND: Extracellular free water (FW) has important roles in the occurrence and development of white matter hyperintensity (WMH). PURPOSE: To explore the correlations between FW and WMH burden. MATERIAL AND METHODS: A prospective analysis was conducted using magnetic resonance imaging (MRI) data from 126 individuals. WMH burden was determined based on WMH volumes and Fazekas scores from deep and periventricular white matter hyperintensity (DWMH and PWMH, respectively) in fluid-attenuated inversion recovery (FLAIR) images. FW values were taken from diffusion tensor imaging (DTI). RESULTS: Univariate analysis showed that FW values were correlated with WMH burden, including WMH volumes and DWMH and PWMH Fazekas scores (P < 0.05). After multivariate analysis, FW values were correlated with WMH volumes and DWMH and PWMH Fazekas scores when adjusted for age and hypertension (P < 0.05). CONCLUSION: Using MRI, increasing extracellular FW was related to WMH burden.

Outcome Prediction by Diffusion Tensor Imaging (DTI) in Patients with Traumatic Injuries of the Median Nerve.

Background/Objectives: The accurate quantification of peripheral nerve axonal regeneration after injury is critically important. Current strategies are limited to detecting early reinnervation. DTI is an MRI modality permitting the assessment of fractional anisotropy, which increases with axonal regeneration. The aim of this pilot study is to evaluate DTI as a potential predictive factor of clinical outcome after median nerve section and microsurgical repair. Methods: We included 10 patients with a complete section of the median nerve, who underwent microsurgical repair up to 7 days after injury. The follow-up period was 1 year, including the current strategy with clinical visits, the Rosén-Lundborg score and electroneuromyography. Additionally, DTI MRI of the injured wrist was planned 1, 3 and 12 months post-operatively and once for the contralateral wrist. Results: The interobserver reliability of DTI measures was almost perfect (ICC 0.802). We report an early statistically significant increase in the fractional anisotropy value after median nerve repair, especially in the region located distal to the suture. Meanwhile, Rosén-Lundborg score gradually increased between the third and sixth month, and continued to increase between the sixth and twelfth month. Conclusions: DTI outcomes three months post-operation could offer greater predictability compared to current strategies. This would enable faster decision-making regarding the need for a potential re-operation in cases of inadequate early reinnervation.

Similarity and characterization of structural and functional neural connections within species under isoflurane anesthesia in the common marmoset.

The common marmoset is an essential model for understanding social cognition and neurodegenerative diseases. This study explored the structural and functional brain connectivity in a marmoset under isoflurane anesthesia, aiming to statistically overcome the effects of high inter-individual variability and noise-related confounds such as physiological noise, ensuring robust and reliable data. Similarities and differences in individual subject data, including assessments of functional and structural brain connectivities derived from resting-state functional MRI and diffusion tensor imaging were meticulously captured. The findings highlighted the high consistency of structural neural connections within the species, indicating a stable neural architecture, while functional connectivity under anesthesia displayed considerable variability. Through independent component and dual regression analyses, several distinct brain connectivities were identified, elucidating their characteristics under anesthesia. Insights into the structural and functional features of the marmoset brain from this study affirm its value as a neuroscience research model, promising advancements in the field through fundamental and translational studies.

Atrophy in the supramarginal gyrus associated with impaired cognitive inhibition in grieving Chinese Shidu parents.

Background: The loss of an only child, known as Shidu in China, is a profoundly distressing experience, often leading to Prolonged Grief Disorder (PGD). Despite its impact, the structural brain alterations associated with PGD, potentially influencing cognitive impairments in Shidu parents, remain understudied.Objective: This study aims to identify brain structural abnormalities related to prolonged grief and their relation with cognitive inhibition in Shidu parents.Methods: The study included 40 Shidu parents and 42 non-bereaved participants. Prolonged grief was evaluated using the Prolonged Grief Questionnaire (PG-13). We employed voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) to assess brain structural alterations and their correlation with cognitive inhibition, as measured by Stroop interference scores.Results: Findings suggest that greater prolonged grief intensity correlates with reduced grey matter volume in the right amygdala and the left supramarginal gyrus (SMG). Additionally, enhanced amygdala-to-whole-brain structural connectivity showed a marginal association with prolonged grief, particularly with emotional-related symptoms. Furthermore, a decrease in SMG volume was found to mediate the relation between prolonged grief and Stroop Time Inference (TI) score, indicating an indirect effect of prolonged grief on cognitive inhibition.Conclusions: The study provides insight into the neural correlates of prolonged grief in Shidu parents, highlighting the SMG's role in cognitive inhibition. These findings emphasise the need for comprehensive grief interventions to address the complex cognitive and emotional challenges faced by this unique bereaved population.

The Shidu parents had a delay in cognitive inhibition when performing the Stroop test, compared to the control group.Prolonged grief intensity was linked to decreased grey matter in the right amygdala and a potential increase in amygdala-to-whole-brain structural connectivity. These volumes were associated with prolonged grief symptoms related to emotions.A higher level of prolonged grief was also associated with reduced grey matter volume in the left supramarginal gyrus, mediating the relationship between prolonged grief and Stroop Time Inference score, which indicates cognitive inhibition.

Modeling electrical impedance in brain tissue with diffusion tensor imaging for functional neurosurgery applications.

Objective.Decades ago, neurosurgeons used electrical impedance measurements in the brain for coarse intraoperative tissue differentiation. Over time, these techniques were largely replaced by more refined imaging and electrophysiological localization. Today, advanced methods of diffusion tensor imaging (DTI) and finite element method (FEM) modeling may permit non-invasive, high-resolution intracerebral impedance prediction. However, expectations for tissue-impedance relationships and experimentally verified parameters for impedance modeling in human brains are lacking. This study seeks to address this need.Approach.We used FEM to simulate high-resolution single- and dual-electrode impedance measurements along linear electrode trajectories through (1) canonical gray and white matter tissue models, and (2) selected anatomic structures within whole-brain patient DTI-based models. We then compared intraoperative impedance measurements taken at known locations along deep brain stimulation (DBS) surgical trajectories with model predictions to evaluate model accuracy and refine model parameters.Main results.In DTI-FEM models, single- and dual-electrode configurations performed similarly. While only dual-electrode configurations were sensitive to white matter fiber orientation, other influences on impedance, such as white matter density, enabled single-electrode impedance measurements to display significant spatial variation even within purely white matter structures. We compared 308 intraoperative single-electrode impedance measurements in five DBS patients to DTI-FEM predictions at one-to-one corresponding locations. After calibration of model coefficients to these data, predicted impedances reliably estimated intraoperative measurements in all patients (R=0.784±0.116, n=5). Through this study, we derived an updated value for the slope coefficient of the DTI conductance model published by Tuch et al., k=0.0649 S·s/mm3(original k=0.844), for use specifically in humans at physiological frequencies.Significance.This is the first study to compare impedance estimates from imaging-based models of human brain tissue to experimental measurements at the same locations in vivo. Accurate, non-invasive, imaging-based impedance prediction has numerous applications in functional neurosurgery, including tissue mapping, intraoperative electrode localization, and DBS.

Properties of the prefrontal tracts and cingulum bundle in children with prenatal alcohol exposure.

BACKGROUND: Prenatal alcohol exposure (PAE) significantly impacts brain structure and function, including cognition and behavior. The cingulum bundle and frontal lobe mediate social-, emotional- and cognitive-related functioning that are affected by PAE. However, the neurobehavioural development of the cingulum and intra-frontal tracts has not been examined in people with PAE. METHODS: We recruited 29 children and adolescents with PAE and 42 age- and gender-matched unexposed controls. Diffusion magnetic resonance imaging (MRI) data were acquired on a 3 T scanner. The rostral, dorsal and parahippocampal cingulum as well as medio-orbitofrontal, lateral-orbitofrontal, dorsolateral-prefrontal and medial-prefrontal tracts, were delineated and their fractional anisotropy and mean (MD), radial (RD), and axial (AD) diffusivities were calculated using constrained spherical deconvolution and deterministic tractography. We measured behavioural and emotional difficulties using the Behavior Assessment System for Children, 2nd Edition, Parent Rating Scale, and then explored their associations with diffusion metrics that differed between groups. RESULTS: We found lower MD, RD, and AD in the right parahippocampal cingulum and multiple intra-frontal tracts in youth with PAE compared to controls; however, these differences did not withstand correction for multiple comparisons. While, youth with PAE showed significantly more emotional and behavioural difficulties compared to unexposed controls, these challenges were not associated with differences in diffusion metrics between groups. CONCLUSION: PAE may be weakly associated with restricted diffusion in the right parahippocampal cingulum and multiple intra-frontal tracts. However, diffusivity changes related to PAE might not be the primary contributor to emotional and behavioural challenges in children and adolescents with PAE.