Search Results (394)

Background/Objectives: Olfaction is in many ways the least understood sensory modality. Its organization and connectivity are still under debate. The aim of this study was to investigate the anatomy of the olfactory system by using a cadaver fiber dissection technique and in vivo tractography to attain a deeper understanding of the subcortical connectivity and organization. Methods: Ten cerebral hemispheres were used in this study for white matter dissection according to Klingler’s technique. Measurements of different cortical structures and interhemispheric symmetry were compared. Diffusion tensor imaging sequences from twenty-five healthy individuals from the Human Connectome Project dataset were used to explore the connectivity of the olfactory system using DSI Studio. White matter connectivity between the following were reconstructed in vivo: (1) Olfactory bulb to primary olfactory cortices; (2) Olfactory bulb to secondary olfactory cortices; (3) Primary to secondary olfactory cortices. The DTI metrics of the identified major associative, projection and commissural pathways were subsequently correlated with olfactory function and cognition in seventy-five healthy individuals with Spearman’s rank correlation and the Benjamini–Hochberg method for false discoveries (CI 95%, p < 0.05) using R. Results: 1. The dissection showed that the lateral stria was significantly longer on the left side and projected towards the amygdala, the entorhinal and piriform cortex. 2. The medial stria was not evident as a consistent white matter structure. 3. Both dissection and tractography showed that major associative white matter pathways such as the uncinate fasciculus, the inferior fronto-occipital fasciculus and cingulum supported the connectivity between olfactory areas together with the anterior commissure. 4. No significant correlation was found between DTI metrics and sensory or cognition test results. Conclusions: We present the first combined fiber dissection analysis and tractography of the olfactory system. We propose a novel definition where the primary olfactory network is defined by the olfactory tract/bulb and primary olfactory cortices through the lateral stria only. The uncinate fasciculus, inferior fronto-occipital fasciculus and cingulum are the associative pathways supporting the connectivity between primary and secondary olfactory areas together with the anterior commissure. We suggest considering these structures as a secondary olfactory network. Further work is needed to attain a deeper understanding of the pathological and physiological implications of the olfactory system. Full article

Background/Objectives: Cerebral palsy (CP), often caused by early brain injury such as perinatal stroke or hemorrhage, is the most common lifelong motor disability. Early identification of at-risk infants and timely access to rehabilitation interventions are essential for improving long-term outcomes. The General Movements Assessment (GMA), performed in the first months of life, has high sensitivity and specificity to predict CP; however, the neurological correlates of general movements remain unclear. This analysis aimed to investigate the relationship between white matter integrity and general movements in infants with perinatal brain injury using advanced neuroimaging techniques. Methods: Diffusion-weighted MRI data were analyzed in 17 infants, 12 with perinatal brain injury and 5 typically developing infants. Tractography was used to identify the corticospinal tract, a key motor pathway often affected by perinatal brain injury, and tract-based spatial statistics (TBSS) were used to examine broader white matter networks. Diffusion parameters from the diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) models were compared between infants with and without typical general movements. Results: Corticospinal tract integrity did not differ between groups when averaged across hemispheres. However, infants with asymmetric general movements exhibited greater corticospinal tract asymmetries. A subset of infants with atypical general movement trajectories at <6 weeks and 3–5 months of age showed reduced corticospinal tract integrity compared to those with typical general movements. TBSS revealed significant differences in white matter integrity between infants with typical and atypical general movements in several white matter pathways, including the corpus callosum, the right posterior corona radiata, bilateral posterior thalamic radiations, the left fornix/stria terminalis, and bilateral tapetum. Conclusions: These findings support and expand upon previous research suggesting that white matter integrity across multiple brain regions plays a role in the formation of general movements. Corticospinal integrity alone was not strongly associated with general movements; interhemispheric and cortical-subcortical connectivity appear critical. These findings underscore the need for further research in larger, diverse populations to refine early biomarkers of neurodevelopmental impairment and guide targeted interventions. Full article

Background/Objectives: Parkinson’s disease (PD) is characterized by progressive neurodegeneration affecting both motor and non-motor functions. Identifying early alterations in PD patients before the onset of dopaminergic therapy is crucial for understanding disease progression and developing targeted interventions. This study aimed to investigate early changes in the putamen and thalamus in de novo PD patients using diffusion tensor imaging (DTI) compared to healthy controls. Methods: Thirty-one de novo PD patients and thirty-three healthy controls underwent DTI scanning. Tract-based spatial statistics were used to compare fractional anisotropy (FA) values between groups. Results: De novo PD patients exhibited significantly lower FA values in the right thalamus compared to controls, suggesting alterations in neuronal integrity or fiber degeneration in the early stages of the disease. However, no significant differences were demonstrated for FA values in the putamen between groups. Conclusions: We demonstrated that the FA value in the right thalamus was lower in PD compared with healthy controls. These findings highlight the potential of DTI as a non-invasive tool for detecting early neural changes in PD patients. Further studies would be helpful to assess the clinical utility of serial FA measurements of the subcortical gray matter in objective quantification of disease progression and monitoring of the therapeutic response. Full article

Background: Inherited white matter (WM) disorders of the central nervous systems (CNS), or leukodystrophies, are devastating diseases that primarily affect children, many of whom die early in life or suffer from long-term disability. Methods: q-Space diffusion MR imaging (QSI) and diffusion tensor MR imaging (DTI) with the same resolution and timing parameters were used to study the spinal cords (SCs) of two myelin mutants that are experimental models of WM diseases of different severity, namely the 28-day-old taiep and Long–Evans Shaker (les) rats. The aim was to verify if and which of the diffusion methodologies used is more suitable for early detection of the milder taiep pathology and to characterize its early phase. We also aimed to compare the diffusion MRI results with quantitative electron microscopy (EM) findings. Results: We found that at this early age (28 days), both QSI and DTI were able to detect the severe les WM pathology, while the milder WM pathology in the SC of the taiep rats was detected only by QSI. An increase in the mean radial displacement (RaDis), representing the MRI axon diameter (AD), and a decrease in the probability for zero displacement (PZD) were observed in the dorsal column (ROI 1) of the taiep SCs. In other WM areas, the same trends were observed but the differences were not of statistical significance. In DTI, we found some lower fractional anisotropy (FA) values in the taiep SCs compared to the controls; however, these differences were not statistically significant. For the more severe les pathology, we observed a dramatic increase in the RaDis values and a large decrease in PZD values in all ROIs examined. There, even the FA values were lower than that of the control SCs in all ROIs, albeit with much smaller statistical significance. These MRI results, which show a higher detectability of WM pathology with heavier diffusion weighting, followed histological findings that showed significant myelin deficiency in the dorsal column in the taiep SCs and a practically complete myelin loss in all WM areas in the les SCs. This study also revealed that, under the experimental conditions used here, the apparent increase in RaDis agrees better with myelin thickness and not with average AD extracted form EM, probably reflecting the effect of water exchange. Conclusions: These results, corroborated by diffusion time-dependent QSI, also imply that while diffusion MRI in general and QSI in particular provide acceptable apparent axon diameter estimations in heathy and mature WM, this appears not to be the case in severely damaged WM where exchange appears to play a more important role. Full article

Background/Objectives: Infant FreeSurfer was introduced to address robust quantification and segmentation in the infant brain. The purpose of this study is to develop a new model for predicting the long-term neurodevelopmental outcomes of very low birth weight preterm infants using automated volumetry extracted from term-equivalent age (TEA) brain MRIs, diffusion tensor imaging, and clinical information. Methods: Preterm infants hospitalized at Severance Children’s Hospital, born between January 2012 and December 2019, were consecutively enrolled. Inclusion criteria included infants with birth weights under 1500 g who underwent both TEA MRI and Bayley Scales of Infant and Toddler Development, Second Edition (BSID-II), assessments at 18–24 months of corrected age (CA). Brain volumetric information was derived from Infant FreeSurfer using 3D T1WI of TEA MRI. Mean and standard deviation of fractional anisotropy of posterior limb of internal capsules were measured. Demographic information and comorbidities were used as clinical information. Study cohorts were split into training and test sets with a 7:3 ratio. Random forest and logistic regression models were developed to predict low Psychomotor Development Index (PDI < 85) and low Mental Development Index (MDI < 85), respectively. Performance metrics, including the area under the receiver operating curve (AUROC), accuracy, sensitivity, precision, and F1 score, were evaluated in the test set. Results: A total of 150 patient data were analyzed. For predicting low PDI, the random forest classifier was employed. The AUROC values for models using clinical variables, MR volumetry, and both clinical variables and MR volumetry were 0.8435, 0.7281, and 0.9297, respectively. To predict low MDI, a logistic regression model was chosen. The AUROC values for models using clinical variables, MR volumetry, and both clinical variables and MR volumetry were 0.7483, 0.7052, and 0.7755, respectively. The model incorporating both clinical variables and MR volumetry exhibited the highest AUROC values for both PDI and MDI prediction. Conclusions: This study presents a promising new prediction model utilizing an automated volumetry algorithm to distinguish long-term psychomotor developmental outcomes in preterm infants. Further research and validation are required for its clinical application. Full article

Background: Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent, heterogeneous neurodevelopmental disorder. Methods: This study presents, for the first time, a comprehensive investigation of white matter microstructural differences between familial ADHD (ADHD-F) and non-familial ADHD (ADHD-NF) using advanced diffusion tensor imaging analyses in a large community-based sample. Results: Children with ADHD-F exhibited significantly greater volume in the right anterior thalamic radiations and the left inferior fronto-occipital fasciculus compared to controls, and greater volume in the left inferior longitudinal fasciculus relative to ADHD-NF. The ADHD-NF group showed reduced fractional anisotropy in the left inferior longitudinal fasciculus compared to the controls. In both the ADHD-F and ADHD-NF groups, a greater volume of anterior thalamic radiation significantly contributed to reduced ADHD symptoms. Conclusions: Our findings suggest that white matter microstructural alterations along the frontal-thalamic pathways may play a critical role in hereditary factors among children with ADHD-F and significantly contribute to elevated inattentive and hyperactive/impulsive behaviors in the affected children. Full article

Background: This study used diffusion tensor imaging (DTI) to detect brain microstructural changes in participants with mild traumatic brain injury (mTBI) who experienced post-traumatic headaches, a common issue that affects quality of life and rehabilitation. Despite its prevalence, the mechanisms behind post-traumatic headache are not well understood. Methods: Participants were recruited from Level 1 trauma centers, and MRI scans, including T1-weighted anatomical imaging and DTI, were acquired 1 month post-injury. Advanced imaging techniques corrected artifacts and extracted diffusion tensor measures reflecting white-matter integrity. Pain sensitivity assays were collected at 1 and 6 months post-injury, including quantitative sensory testing and psychological assessments. Results: Significant aberrations in axial diffusivity in the forceps major were observed in mTBI participants (n = 12) compared to healthy controls (n = 10) 1 month post-injury (p = 0.02). Within the mTBI group, DTI metrics at 1 month were significantly associated with pain-related and psychological outcomes at 6 months. Statistical models revealed group differences in the right sagittal stratum (p < 0.01), left insula (p < 0.04), and left superior longitudinal fasciculus (p < 0.05). Conclusions: This study shows that DTI metrics at 1 month post-injury are sensitive to mTBI and predictive of chronic pain and psychological outcomes at 6 months. Full article

Background and objectives: Type 2 diabetes mellitus (T2DM) affects brain white matter microstructure. While diffusion tensor imaging (DTI) has been used to study white matter abnormalities in T2DM, it lacks specificity for complex white matter tracts. Neurite orientation dispersion and density imaging (NODDI) offers a more specific approach to characterising white matter microstructures. This study aims to explore white matter alterations in T2DM using both DTI and NODDI and assess their association with disease duration and glycaemic control, as indicated by HbA1c levels. Methods and Materials: We analysed white matter microstructure in 48 tracts using data from the UK Biobank, involving 1023 T2DM participants (39% women, mean age 66) and 30,744 non-T2DM controls (53% women, mean age 64). Participants underwent 3.0T multiparametric brain imaging, including T1-weighted and diffusion imaging for DTI and NODDI. We performed region-of-interest analyses on fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), orientation dispersion index (ODI), intracellular volume fraction (ICVF), and isotropic water fraction (IsoVF) to assess white matter abnormalities. Results: We observed reduced FA and ICVF, and increased MD, AD, RD, ODI, and IsoVF in T2DM participants compared to controls (p < 0.05). These changes were associated with longer disease duration and higher HbA1c levels (0 < r ≤ 0.2, p < 0.05). NODDI identified microstructural changes in white matter that were proxies for reduced neurite density and disrupted fibre orientation, correlating with disease progression and poor glucose control. In conclusion, NODDI contributed to DTI in capturing white matter differences in participants with type 2 diabetes, suggesting the feasibility of NODDI in detecting white matter alterations in type 2 diabetes. Type 2 diabetes can cause white matter microstructural abnormalities that have associations with glucose control. Conclusions: The NODDI diffusion model allows the characterisation of white matter neuroaxonal pathology in type 2 diabetes, giving biophysical information for understanding the impact of type 2 diabetes on brain microstructure. Future research should focus on the longitudinal tracking of these microstructural changes to better understand their potential as early biomarkers for cognitive decline in T2DM. Full article

Current research on the effects of childhood trauma largely focuses on maltreatment. In the current study, we used diffusion tensor imaging (DTI) to determine the association between potentially traumatic exposures not related to maltreatment and fractional anisotropy (FA) in 184 youth aged 9–14 years. The Trauma History Profile was used to determine how many traumatic events in different categories were experienced and create low- and high-trauma groups. FA values were compared between groups in twelve a priori chosen regions of interest (ROIs). Five of the twelve regions showed significantly lower FA in the high-trauma groups when compared to the low-trauma groups, including the body of the corpus callosum, the total corpus callosum, bilateral posterior thalamic radiation, and the left cingulate gyrus projection of the cingulum bundle. Group differences were also observed across a range of behaviors. However, FA was not associated with posttraumatic stress symptomology. The results support the hypothesis that the high-trauma group had lower FA compared to the low-trauma group. The significant ROIs represent a subset of regions identified in studies of adults exposed to traumatic childhood events or children with a history of maltreatment. These results, obtained from typically developing youth, underline the importance of examining childhood trauma exposure in future developmental studies. Full article

Early neurological deterioration is associated with poor functional outcomes in stroke patients, but the underlying mechanisms remain unclear. This study aims to understand the progression of stroke-related brain damage using a rhesus monkey model with ischemic occlusion. Multiparameter MRI was used to monitor the progressive evolution of the brain lesion following stroke. Resting-state functional MRI, dynamic susceptibility contrast perfusion MRI, diffusion tensor imaging, and T1- and T2-weighted scans were acquired prior to surgery and at 4–6 h, 48 h, and 96 h following the stroke. The results revealed a sudden increase in infarction volume after the hyper-acute phase but before 48 h on diffusion-weighted imaging (DWI), with a slight extension by 96 h. Lower relative cerebral blood flow (CBF) and time to maximum (Tmax) prior to the stroke, along with a progressive decrease post-stroke, were observed when compared to other stroke monkeys in the same cohort. Functional connectivity (FC) in the ipsilesional secondary somatosensory cortex (S2) and primary motor cortex (M1) exhibited an immediate decline on Day 0 compared to baseline and followed by a slight increase on Day 2 and a further decrease on Day 4. These findings provide valuable insights into infarction progression, emphasizing the critical role of collateral circulation and its impact on early neurological deterioration during acute stroke. Full article

Meticulous clinical examination is essential for spinal disorders to utilize the diagnostic methods and technologies that strongly support physicians and enhance clinical practice. A significant change in the approach to diagnosing spinal disorders has occurred in the last three decades, which has enhanced a more nuanced understanding of spine pathology. Traditional radiographic methods such as conventional and functional X-rays and CT scans are still the first line in the diagnosis of spinal disorders due to their low cost and accessibility. As more advanced imaging technologies become increasingly available worldwide, there is a constantly increasing trend in MRI scans for detecting spinal pathologies and making treatment decisions. Not only do MRI scans have superior diagnostic capabilities, but they also assist surgeons in performing meticulous preoperative planning, making them currently the most widely used diagnostic tool for spinal disorders. Positron Emission Tomography (PET) can help detect inflammatory lesions, infections, and tumors. Other advanced diagnostic tools such as CT/MRI fusion image, Functional Magnetic Resonance Imaging (fMRI), Upright and Kinetic MRI, magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI) could play an important role when it comes to detecting more special pathologies. However, some technical difficulties in the daily praxis and their high costs act as obstacles to their further spread. Integrating artificial intelligence and advancements in data analytics and virtual reality promises to enhance spinal procedures’ precision, safety, and efficacy. As these technologies continue to develop, they will play a critical role in transforming spinal surgery. This paradigm shift emphasizes the importance of continuous innovation and adaptability in improving the diagnosis and treatment of spinal disorders. Full article

The long-term impact of stroke on Alzheimer’s disease (AD) progression, particularly regarding sex-specific differences, remains unknown. Using a longitudinal study design, we investigated transient middle cerebral artery occlusion in 3.5-month-old APP_swe/PS1_dE9 (APP/PS1) and wild-type mice. In vivo, we assessed behavior, cerebral blood flow (CBF), and structural integrity by neuroimaging, as well as post-mortem myelin integrity (polarized light imaging, PLI), neuroinflammation, and amyloid beta (Aβ) deposition. APP/PS1 mice exhibited cognitive decline, white matter degeneration (reduced fractional anisotropy (FA) via diffusion tensor imaging (DTI)), and decreased myelin density via PLI. Despite early hypertension, APP/PS1 mice showed only sporadic hypoperfusion. Cortical thickening and hippocampal hypertrophy likely resulted from Aβ accumulation and neuroinflammation. Stroke-operated mice retained cognition despite cortical thinning and hippocampal atrophy due to cerebrovascular adaptation, including increased CBF in the hippocampus and thalamus. Stroke did not worsen AD pathology, nor did AD exacerbate stroke outcomes. Sex differences were found: female APP/PS1 mice had more severe Aβ deposition, hyperactivity, lower body weight, and reduced CBF but less neuroinflammation, suggesting potential neuroprotection. These findings highlight white matter degeneration and Aβ pathology as key drivers of cognitive decline in AD, with stroke-related deficits mitigated by (cerebro)vascular adaptation. Sex-specific therapies are crucial for AD and stroke. Full article

Purpose: Accurate and precise navigation in space and postural stability rely on the central integration of multisensory input (vestibular, proprioceptive, visual), weighted according to its reliability, to continuously update the internal estimate of the direction of gravity. In this study, we examined both peripheral and central vestibular functions in a world-renowned 53-year-old male tightrope walker and investigated the extent to which his exceptional performance was reflected in our findings. Methods: Comprehensive assessments were conducted, including semicircular canal function tests (caloric irrigation, rotatory-chair testing, video head impulse testing of all six canals, dynamic visual acuity) and otolith function evaluations (subjective visual vertical, fundus photography, ocular/cervical vestibular-evoked myogenic potentials [oVEMPs/cVEMPs]). Additionally, static and dynamic posturography, as well as video-oculography (smooth-pursuit eye movements, saccades, nystagmus testing), were performed. The participant’s results were compared to established normative values. High-resolution diffusion tensor magnetic resonance imaging (DT-MRI) was utilized to assess motor tract integrity. Results: Semicircular canal testing revealed normal results except for a slightly reduced response to right-sided caloric irrigation (26% asymmetry ratio; cut-off = 25%). Otolith testing, however, showed marked asymmetry in oVEMP amplitudes, confirmed with two devices (37% and 53% weaker on the left side; cut-off = 30%). Bone-conducted cVEMP amplitudes were mildly reduced bilaterally. Posturography, video-oculography, and subjective visual vertical testing were all within normal ranges. Diffusion tensor MRI revealed no structural abnormalities correlating with the observed functional asymmetry. Conclusions: This professional tightrope walker’s exceptional balance skills contrast starkly with significant peripheral vestibular (otolithic) deficits, while MR imaging, including diffusion tensor imaging, remained normal. These findings highlight the critical role of central computational mechanisms in optimizing multisensory input signals and fully compensating for vestibular asymmetries in this unique case. Full article

Recent interest in musculoskeletal connective tissues like tendons, aponeurosis, and deep fascia has led to a greater focus on in vivo medical imaging, particularly MRI. Given the rapid T₂* decay of collagenous tissues, advanced ultra-short echo time (UTE) MRI sequences have proven useful in generating high-signal images of these tissues. To further these advances, we discuss the integration of UTE with Diffusion Tensor Imaging (DTI) and explore image processing techniques to enhance the localization, labeling, and modeling of connective tissues. These techniques are especially valuable for extracting features from thin tissues that may be difficult to distinguish. We present data from lower leg scans of 30 healthy subjects using a non-Cartesian MRI sequence to acquire axial 2D images to segment skeletal muscle and connective tissue. DTI helped differentiate aponeurosis from deep fascia by analyzing muscle fiber orientations. The dual echo imaging methods yielded high-resolution images of deep fascia, where in-plane spatial resolutions were between 0.3 × 0.3 mm to 0.5 × 0.5 mm with a slice thickness of 3–5 mm. Techniques such as K-Means clustering, FFT edge detection, and region-specific scaling were most effective in enhancing images of deep fascia, aponeurosis, and tendon to enable high-fidelity modeling of these tissues. Full article

Purpose: Early treatment response assessments are crucial, and the results are known to better correlate with prognosis and survival outcomes. The present study was conducted to differentiate true progression (TP) from pseudoprogression (PsP) in long-term-surviving glioblastoma patients using our previously established multiparametric MRI-based predictive model, as well as to identify clinical factors impacting survival outcomes in these patients. Methods: We report six patients with glioblastoma that had an overall survival longer than 5 years. When tumor specimens were available from second-stage surgery, histopathological analyses were used to classify between TP (>25% characteristics of malignant neoplasms; n = 2) and PsP (<25% characteristics of malignant neoplasms; n = 2). In the absence of histopathology, modified RANO criteria were assessed to determine the presence of TP (n = 1) or PsP (n = 1). The predictive probabilities (PPs) of tumor progression were measured from contrast-enhancing regions of neoplasms using a multiparametric MRI-based prediction model. Subsequently, these PP values were used to define each lesion as TP (PP ≥ 50%) or PsP (PP < 50%). Additionally, detailed clinical information was collected. Results: Our predictive model correctly identified all patients with TP (n = 3) and PsP (n = 3) cases, reflecting a significant concordance between histopathology/modified RANO criteria and PP values. The overall survival varied from 5.1 to 12.3 years. Five of the six glioblastoma patients were MGMT promoter methylated. All patients were female, with a median age of 56 years. Moreover, all six patients had a good functional status (KPS ≥ 70), underwent near-total/complete resection, and received alternative therapies. Conclusions: Multiparametric MRI can aid in assessing treatment response in long-term-surviving glioblastoma patients. Full article