Interhemispheric Structural Connectivity Underlies Motor Recovery after Stroke.

OBJECTIVE: Although ample evidence highlights that the ipsilesional corticospinal tract (CST) plays a crucial role in motor recovery after stroke, studies on cortico-cortical motor connections remain scarce and provide inconclusive results. Given their unique potential to serve as structural reserve enabling motor network reorganization, the question arises whether cortico-cortical connections may facilitate motor control depending on CST damage. METHODS: Diffusion spectrum imaging (DSI) and a novel compartment-wise analysis approach were used to quantify structural connectivity between bilateral cortical core motor regions in chronic stroke patients. Basal and complex motor control were differentially assessed. RESULTS: Both basal and complex motor performance were correlated with structural connectivity between bilateral premotor areas and ipsilesional primary motor cortex (M1) as well as interhemispheric M1 to M1 connectivity. Whereas complex motor skills depended on CST integrity, a strong association between M1 to M1 connectivity and basal motor control was observed independent of CST integrity especially in patients who underwent substantial motor recovery. Harnessing the informational wealth of cortico-cortical connectivity facilitated the explanation of both basal and complex motor control. INTERPRETATION: We demonstrate for the first time that distinct aspects of cortical structural reserve enable basal and complex motor control after stroke. In particular, recovery of basal motor control may be supported via an alternative route through contralesional M1 and non-crossing fibers of the contralesional CST. Our findings help to explain previous conflicting interpretations regarding the functional role of the contralesional M1 and highlight the potential of cortico-cortical structural connectivity as a future biomarker for motor recovery post-stroke. ANN NEUROL 2023;94:785-797.

Early motor network connectivity after stroke: An interplay of general reorganization and state-specific compensation.

Motor recovery after stroke relies on functional reorganization of the motor network, which is commonly assessed via functional magnetic resonance imaging (fMRI)-based resting-state functional connectivity (rsFC) or task-related effective connectivity (trEC). Measures of either connectivity mode have been shown to successfully explain motor impairment post-stroke, posing the question whether motor impairment is more closely reflected by rsFC or trEC. Moreover, highly similar changes in ipsilesional and interhemispheric motor network connectivity have been reported for both rsFC and trEC after stroke, suggesting that altered rsFC and trEC may capture similar aspects of information integration in the motor network reflecting principle, state-independent mechanisms of network reorganization rather than state-specific compensation strategies. To address this question, we conducted the first direct comparison of rsFC and trEC in a sample of early subacute stroke patients (n = 26, included on average 7.3 days post-stroke). We found that both rsFC and trEC explained motor impairment across patients, stressing the clinical potential of fMRI-based connectivity. Importantly, intrahemispheric connectivity between ipsilesional M1 and premotor areas depended on the activation state, whereas interhemispheric connectivity between homologs was state-independent. From a mechanistic perspective, our results may thus arise from two distinct aspects of motor network plasticity: task-specific compensation within the ipsilesional hemisphere and a more fundamental form of reorganization between hemispheres.

Acute ischaemic stroke alters the brain's preference for distinct dynamic connectivity states.

Acute ischaemic stroke disturbs healthy brain organization, prompting subsequent plasticity and reorganization to compensate for the loss of specialized neural tissue and function. Static resting state functional MRI studies have already furthered our understanding of cerebral reorganization by estimating stroke-induced changes in network connectivity aggregated over the duration of several minutes. In this study, we used dynamic resting state functional MRI analyses to increase temporal resolution to seconds and explore transient configurations of motor network connectivity in acute stroke. To this end, we collected resting state functional MRI data of 31 patients with acute ischaemic stroke and 17 age-matched healthy control subjects. Stroke patients presented with moderate to severe hand motor deficits. By estimating dynamic functional connectivity within a sliding window framework, we identified three distinct connectivity configurations of motor-related networks. Motor networks were organized into three regional domains, i.e. a cortical, subcortical and cerebellar domain. The dynamic connectivity patterns of stroke patients diverged from those of healthy controls depending on the severity of the initial motor impairment. Moderately affected patients (n = 18) spent significantly more time in a weakly connected configuration that was characterized by low levels of connectivity, both locally as well as between distant regions. In contrast, severely affected patients (n = 13) showed a significant preference for transitions into a spatially segregated connectivity configuration. This configuration featured particularly high levels of local connectivity within the three regional domains as well as anti-correlated connectivity between distant networks across domains. A third connectivity configuration represented an intermediate connectivity pattern compared to the preceding two, and predominantly encompassed decreased interhemispheric connectivity between cortical motor networks independent of individual deficit severity. Alterations within this third configuration thus closely resembled previously reported ones originating from static resting state functional MRI studies post-stroke. In summary, acute ischaemic stroke not only prompted changes in connectivity between distinct networks, but it also caused characteristic changes in temporal properties of large-scale network interactions depending on the severity of the individual deficit. These findings offer new vistas on the dynamic neural mechanisms underlying acute neurological symptoms, cortical reorganization and treatment effects in stroke patients.

Local neuronal sleep after stroke: The role of cortical bistability in brain reorganization.

BACKGROUND: Acute cerebral ischemia triggers a number of cellular mechanisms not only leading to excitotoxic cell death but also to enhanced neuroplasticity, facilitating neuronal reorganization and functional recovery. OBJECTIVE: Transferring these cellular mechanisms to neurophysiological correlates adaptable to patients is crucial to promote recovery post-stroke. The combination of TMS and EEG constitutes a promising readout of neuronal network activity in stroke patients. METHODS: We used the combination of TMS and EEG to investigate the development of local signal processing and global network alterations in 40 stroke patients with motor deficits alongside neural reorganization from the acute to the chronic phase. RESULTS: We show that the TMS-EEG response reflects information about reorganization and signal alterations associated with persistent motor deficits throughout the entire post-stroke period. In the early post-stroke phase and in a subgroup of patients with severe motor deficits, TMS applied to the lesioned motor cortex evoked a sleep-like slow wave response associated with a cortical off-period, a manifestation of cortical bistability, as well as a rapid disruption of the TMS-induced formation of causal network effects. Mechanistically, these phenomena were linked to lesions affecting ascending activating brainstem fibers. Of note, slow waves invariably vanished in the chronic phase, but were highly indicative of a poor functional outcome. CONCLUSION: In summary, we found evidence that transient effects of sleep-like slow waves and cortical bistability within ipsilesional M1 resulting in excessive inhibition may interfere with functional reorganization, leading to a less favorable functional outcome post-stroke, pointing to a new therapeutic target to improve recovery of function.

Corticospinal premotor fibers facilitate complex motor control after stroke.

OBJECTIVE: The corticospinal tract (CST) is considered the most important motor output pathway comprising fibers from the primary motor cortex (M1) and various premotor areas. Damage to its descending fibers after stroke commonly leads to motor impairment. While premotor areas are thought to critically support motor recovery after stroke, the functional role of their corticospinal output for different aspects of post-stroke motor control remains poorly understood. METHODS: We assessed the differential role of CST fibers originating from premotor areas and M1 in the control of basal (single-joint muscle synergies and strength) and complex motor control (involving inter-joint coordination and visuomotor integration) using a novel diffusion imaging approach in chronic stroke patients. RESULTS: While M1 sub-tract anisotropy was positively correlated with basal and complex motor skills, anisotropy of PMd, PMv, and SMA sub-tracts was exclusively associated with complex motor tasks. Interestingly, patients featuring persistent motor deficits showed an additional positive association between premotor sub-tract integrity and basal motor control. INTERPRETATION: While descending M1 output seems to be a prerequisite for any form of upper limb movements, complex motor skills critically depend on output from premotor areas after stroke. The additional involvement of premotor tracts in basal motor control in patients with persistent deficits emphasizes their compensatory capacity in post-stroke motor control. In summary, our findings highlight the pivotal role of descending corticospinal output from premotor areas for motor control after stroke, which thus serve as prime candidates for future interventions to amplify motor recovery.

Unilateral Variant of NGT Syndrome: An Uncommon Complication of a Very Common Intervention.

The common complications of nasogastric tube placement include gastrointestinal-tube malposition, coiling, or knotting, impaired function of the lower esophageal sphincter leading to reflux of gastric contents, esophagitis, gastrointestinal bleeding, and aspiration pneumonia. Sofferman et al. in 1990, described a clinical entity constituted by life-threatening bilateral vocal cord paralysis, presenting as throat pain, stridor and respiratory compromise as Nasogastric syndrome (NGTS). There are fewer than 50 cases of NGTS described in the literature, till date, let alone a unilateral variant of the same. Here we have described two cases of unilateral variant of NGTS, the management, outcome, and a detailed literature review of the previous reported cases. The two cases described were identified in the same year, highlighting the fact that, the entity might be more common, and needs more clinical attention than previously estimated.

The role of corticospinal and extrapyramidal pathways in motor impairment after stroke.

Anisotropy of descending motor pathways has repeatedly been linked to the severity of motor impairment following stroke-related damage to the corticospinal tract. Despite promising findings consistently tying anisotropy of the ipsilesional corticospinal tract to motor outcome, anisotropy is not yet utilized as a biomarker for motor recovery in clinical practice as several methodological constraints hinder a conclusive understanding of degenerative processes in the ipsilesional corticospinal tract and compensatory roles of other descending motor pathways. These constraints include estimating anisotropy in voxels with multiple fibre directions, sampling biases and confounds due to ageing-related atrophy. The present study addressed these issues by combining diffusion spectrum imaging with a novel compartmentwise analysis approach differentiating voxels with one dominant fibre direction (one-directional voxels) from voxels with multiple fibre directions. Compartmentwise anisotropy for bihemispheric corticospinal and extrapyramidal tracts was compared between 25 chronic stroke patients, 22 healthy age-matched controls, and 24 healthy young controls and its associations with motor performance of the upper and lower limbs were assessed. Our results provide direct evidence for Wallerian degeneration along the entire length of the ipsilesional corticospinal tract reflected by decreased anisotropy in descending fibres compared with age-matched controls, while ageing-related atrophy was observed more ubiquitously across compartments. Anisotropy of descending ipsilesional corticospinal tract voxels showed highly robust correlations with various aspects of upper and lower limb motor impairment, highlighting the behavioural relevance of Wallerian degeneration. Moreover, anisotropy measures of two-directional voxels within bihemispheric rubrospinal and reticulospinal tracts were linked to lower limb deficits, while anisotropy of two-directional contralesional rubrospinal voxels explained gross motor performance of the affected hand. Of note, the relevant extrapyramidal structures contained fibres crossing the midline, fibres potentially mitigating output from brain stem nuclei, and fibres transferring signals between the extrapyramidal system and the cerebellum. Thus, specific parts of extrapyramidal pathways seem to compensate for impaired gross arm and leg movements incurred through stroke-related corticospinal tract lesions, while fine motor control of the paretic hand critically relies on ipsilesional corticospinal tract integrity. Importantly, our findings suggest that the extrapyramidal system may serve as a compensatory structural reserve independent of post-stroke reorganization of extrapyramidal tracts. In summary, compartment-specific anisotropy of ipsilesional corticospinal tract and extrapyramidal tracts explained distinct aspects of motor impairment, with both systems representing different pathophysiological mechanisms contributing to motor control post-stroke. Considering both systems in concert may help to develop diffusion imaging biomarkers for specific motor functions after stroke.

A cross-sectional study from Qatar on the effect of influenza vaccination on the severity of COVID-19.

To assess and compare the severity of corona virus disease 2019 (COVID-19) infection in patients with and without a history of influenza vaccination. In this cross-sectional study descriptive statistics were used to analyze COVID-19-related parameters, including demographics, comorbidities, and severity. Normally distributed data with mean, standard deviation, and 95% confidence interval (CI) were reported, while non-normally distributed data was presented with median and inter-quartile range. Categorical data was summarized using frequencies and percentages. Associations were assessed using Pearson Chi-square, Fisher Exact, t test, or Mann-Whitney U test. Univariate and multivariate logistic regression methods were used to evaluate the relationship between disease severity, clinical outcomes, influenza vaccination status, and other predictors. Significance was considered for p values < 0.05. Statistical analyses were done using SPSS V.27.0 (IBM Corp) and Epi Info (CDC) software. Between March 2020 and December 2020 before the availability of COVID-19 vaccination, 148,215 severe acute respiratory syndrome corona virus 2 positive patients were studied, with 3519 vaccinated against influenza, and 144,696 unvaccinated. After random sampling at 1:2 ratio, the final analysis included 3234 vaccinated and 5640 unvaccinated patients. The majority (95.4%) had mild or asymptomatic COVID-19, while 4.6% had severe or critical cases as defined by World Health Organization severity grading. Multivariate logistic regression analysis revealed that the vaccinated group had significantly less severe (adjusted odds ratio [OR] 0.683; 95% CI 0.513-0.911, P = .009) and critical (adjusted OR 0.345; 95% CI 0.145-0.822, P = .016) COVID-19 and were less likely to require oxygen therapy (adjusted OR 0.696; 95% CI 0.531-0.912, P = .009) after adjusting for confounders like age, gender and comorbidities. No significant differences in Intensive care unit admissions (adjusted OR 0.686; 95% CI 0.425-1.11, P = .122), mechanical ventilation (adjusted OR 0.631; 95% CI 0.308-1.295, P = .209) and mortality (adjusted OR 1.105; 95% CI 0.348-3.503, P = .866) were noted between the 2 groups. Influenza vaccination may significantly reduce the severity of COVID-19 but has no significant effect on intensive care unit admissions, mechanical ventilation and all- cause mortality.

Temperature-dependent Cu and Ag ion mobility and associated changes of transport properties in pavonite-type Cu1.4Ag0.4Bi5.4Se9.

Cu1.4Ag0.4Bi5.4Se9, the first quaternary compound in the system Cu/Ag/Bi/Se, was obtained from the elements by melt synthesis after pre-reaction and annealing steps. It exhibits a 4P pavonite-type crystal structure in the spacegroup C2/m, which consists of NaCl-type building blocks extending in two dimensions that are separated by rods of edge-sharing BiSe7 polyhedra and "clusters" of several partially occupied Cu atom sites. Temperature-dependent single crystal X-ray diffraction up to 350 °C helped to explain thermoelectric properties. Cu atoms occupy more and different disordered sites at ≥200 °C. Ag atoms share Bi atom sites and prefer different sites as a function of temperature. Cu1.4Ag0.4Bi5.4Se9 is a metallic n-type thermoelectric material with Seebeck coefficients up to -150 µV K-1. Lattice thermal conductivity significantly decreases from 0.55 W mK-1 to 0.42 W mK-1 with increasing structural disorder. Cu1.4Ag0.4Bi5.4Se9 may thus be described with the phonon-liquid electron-crystal (PLEC) concept and reaches a figure of merit of zTmax = 0.23 at 450 °C. B-factor analysis based on a single parabolic band model shows that the chemical potential of electrons approaches the one corresponding to optimal charge carrier concentration, especially at higher temperatures. With respect to most properties and the easily reproducible synthesis, the compound can well compete with other sulfosalt-like thermoelectric materials and is considerably less toxic than most of them.

Characterization of Drug Release from Mesoporous SiO2-Based Membranes with Variable Pore Structure and Geometry.

Transdermal drug delivery systems (TDDSs) play important roles in therapy due to distinct advantages over other forms and types of drug application. While common TDDS patches mainly consist of polymeric matrices so far, inorganic carriers show numerous advantages such as high mechanical stability, possible re-use and re-loading of drugs, and a broad chemical compatibility with therapeutically relevant compounds and chemical enhancers. Mesoporous glasses can be prepared in different monolithic shapes, and offer a particularly wide range of possible pore volumes, pore diameters, and specific surface areas. Further, they show high loading capacities and favorable physical, technical, and biological properties. Here, we explored for the first time monolithic SiO2-based carriers as sustained release systems of therapeutic drugs. In an ideally stirred vessel as model system, we systematically analyzed the influence of pore diameter, pore volume, and the dimensions of glass monoliths on the loading and sustained release of different drugs, including anastrozole, xylazine, imiquimod, levetiracetam, and flunixin. Through multilinear regression, we calculated the influence of different parameters on drug loading and diffusion coefficients. The systematic variation of the mesoporous glass properties revealed pore volumes and drug loading concentrations, but not pore diameter or pore surface area as important parameters of drug loading and release kinetics. Other relevant effectors include the occurrence of lateral diffusion within the carrier and drug-specific properties such as adsorption. The structure-property relationships derived from our data will allow further fine-tuning of the systems according to their desired properties as TDDS, thus guiding towards optimal systems for their use in transdermal drug applications.

Metastatic Adenocarcinoma of the Lung Mimicking Miliary Tuberculosis and Pott's Disease.

Tuberculous spondylitis (Pott's disease) is among the frequent extra-pulmonary presentations of tuberculosis (TB). The global incidence of lung adenocarcinoma is on the rise, and it is a rare differential diagnosis of miliary shadows on chest imaging. It has a predilection to metastasize to ribs and spine in particular. There is a very close clinical and radiological resemblance in the presentation of spinal metastasis of lung cancer and Potts's disease. It poses a diagnostic challenge to clinicians particularly in TB endemic areas to arrive at an accurate diagnosis, leading to disease progression and poor outcome. We report a 54-year-old female patient presented with constitutional symptoms of on and off fever and back pain. Her chest X-ray revealed miliary shadows, and acid-fast bacilli (AFB) sputum smear and TB polymerase chain reaction (PCR) test came negative; radiological diagnosis of tuberculous spondylitis was done on computerized tomography (CT) chest and magnetic resonance imaging (MRI) spine. Subsequent bronchoscopy and bronchoalveolar lavage (BAL) cytology showed malignant cells and CT-guided lung biopsy confirmed lung adenocarcinoma with spinal and brain metastasis. Despite being started on chemo-immunotherapy and radiotherapy her outcome was poor due to advanced metastatic disease. This case highlights the significance of considering metastatic adenocarcinoma of the lung a rare but ominous possibility in the differential diagnosis of miliary shadows on chest imaging. Early bronchoscopy and biopsy must be considered in all patients presenting with miliary pulmonary lesions and spinal lesions to make a correct diagnosis, preventing an unnecessary delay in starting proper treatment and poor outcome. It also emphasizes the importance of better understanding the different radiographic features of the two common mimics, spinal tuberculosis, and metastatic spinal tumors.

Dasatinib-induced chylothorax: An unusual presentation of a common adverse event-A case report with literature review.

Tyrosine kinase inhibitors (TKIs) are the key agents for treating CML and BCR-ABL+ B-ALL. Dasatinib is a potent second-generation TKI. Here, we have discussed the case of a 51-year-old gentleman diagnosed with B-myeloid mixed-phenotype acute leukemia with t(9;22)(q34.1;q11.2); BCR-ABL1p210, in complete hematological, cytogenetic, and molecular remission, who developed chylothorax. Though pleural effusion is a commonly observed adverse effect of dasatinib therapy, chylothorax is rare. The ability of Dasatinib to inhibit multiple families of tyrosine kinases could be considered the etiology. Discontinuation of the drug resolved the symptom, but pleural effusion recurred once Dasatinib was resumed. Chylothorax induced by Dasatinib is a differential to be kept in mind, owing to the limited number of cases being reported.

Case Report: Ischemic Colitis in Severe COVID-19 Pneumonia: An Unforeseen Gastrointestinal Complication.

Clinical manifestations and complications of SARS-CoV-2 are still emerging and variant. Gastrointestinal (GI) manifestations and complications are hugely under-recognized. The presence of angiotensin converting enzyme-2 receptors in the intestinal enterocytes, the receptors primarily involved in the pathogenesis of COVID-19 pneumonia, maybe the key factor contributing to the pathogenesis of GI manifestations. Ischemic colitis, although the most common ischemic pathology of the GI tract, is relatively rare, occurring as a result of colonic hypoperfusion. The innumerable causes of colonic ischemia are categorized into occlusive and nonocclusive pathologies. Here, we have discussed a case of severe COVID-19 pneumonia, developing ischemic colitis, as a rare GI complication. The cause of ischemia in COVID-19 pneumonia is multifactorial, including hypercoagulable state, coagulopathy leading to thromboembolic complications, and use of vasopressors in severely ill patients with hemodynamic compromise.