Prevalence of Neurological Soft Signs at Presentation in Pediatric Acute-Onset Neuropsychiatric Syndrome.

Importance: Studies of brain imaging and movements during REM sleep indicate basal ganglia involvement in pediatric acute-onset neuropsychiatric syndrome (PANS). Characterizing neurological findings commonly present in patients with PANS could improve diagnostic accuracy. Objective: To determine the prevalence of neurological soft signs which may reflect basal ganglia dysfunction (NSS-BG) in youth presenting with PANS and whether clinical characteristics of PANS correlate with NSS-BG. Design, Setting, and Participants: 135 new patients who were evaluated at the Stanford Children's Immune Behavioral Health Clinic between November 1, 2014 and March 1, 2020 and met strict PANS criteria were retrospectively reviewed for study inclusion. 16 patients were excluded because they had no neurological exam within the first three visits and within three months of clinical presentation. Main Outcomes and Measures: The following NSS-BG were recorded from medical record review: 1) glabellar tap reflex, 2) tongue movements, 3) milkmaid's grip, 4) choreiform movements, 5) spooning, and 6) overflow movements. We included data from prospectively collected symptoms and impairment scales. Results: The study included 119 patients: mean age at PANS onset was 8.2 years, mean age at initial presentation was 10.4 years, 55.5% were male, and 73.9% were non-Hispanic White. At least one NSS-BG was observed in 95/119 patients (79.8%). Patients had 2.1 NSS-BG on average. Patients with 4 or more NSS-BG had higher scores of global impairment (p=0.052) and more symptoms (p=0.008) than patients with 0 NSS-BG. There was no significant difference in age at visit or reported caregiver burden. On Poisson and linear regression, the number of NSS-BG was associated with global impairment (2.857, 95% CI: 0.092-5.622, p=0.045) and the number of symptoms (1.049, 95% CI: 1.018-1.082, p=0.002), but not age or duration of PANS at presentation. Conclusions and Relevance: We found a high prevalence of NSS-BG in patients with PANS and an association between NSS-BG and disease severity that is not attributable to younger age. PANS may have a unique NSS-BG profile, suggesting that targeted neurological exams may support PANS diagnosis.

Opening Pressure and Post-Lumbar Puncture Headache in Children Undergoing Intrathecal Baclofen Trial.

Aims: Post-lumbar puncture headache occurs in 5% to 12% of children. The purpose of this study was to determine the frequency and predictors of post-lumbar puncture headache in children with hypertonia undergoing lumbar puncture for intrathecal baclofen trial. Methods: This was a retrospective single-center review of all 43 children (<18 years) with hypertonia and/or dyskinesia undergoing intrathecal baclofen trial from 2013-2022. Predictors of post-lumbar puncture headache were evaluated via 2-way paired t test and Fisher exact test. Results: Seven subjects (16.3%) developed post-lumbar puncture headache. Of patients who developed post-lumbar puncture headache, 3 required emergency care or hospitalization. One was misdiagnosed with constipation. The 16 patients without opening pressure measured were excluded from subsequent analyses. Of the 27 patients with documented opening pressure, the mean opening pressure was 24.0 cm H2O (SD 6.5) and 5 (18.5%) had elevated opening pressure (>28 cm H2O). Mean opening pressure was higher for those with post-lumbar puncture headache (28.6 vs 22.4 cm H2O, P = .014). Sixty percent of patients with elevated opening pressure developed post-lumbar puncture headache. Baclofen pumps were placed in 4 (80%) patients with elevated opening pressure and 6 (85.7%) with post-lumbar puncture headaches without complications. Interpretation: The risk of post-lumbar puncture headache after intrathecal baclofen trial was higher than reported in the literature, likely because of greater rates of elevated opening pressure. Physicians may use opening pressure to predict risk for post-lumbar puncture headache and should educate families about symptoms. Elevated opening pressure or post-lumbar puncture headache may not preclude baclofen pump placement.

Stroke Alters the Function of Enteric Neurons to Impair Smooth Muscle Relaxation and Dysregulates Gut Transit.

BACKGROUND: Gut dysmotility is common after ischemic stroke, but the mechanism underlying this response is unknown. Under homeostasis, gut motility is regulated by the neurons of the enteric nervous system that control contractile/relaxation activity of muscle cells in the gut wall. More recently, studies of gut inflammation revealed interactions of macrophages with enteric neurons are also involved in modulating gut motility. However, whether poststroke gut dysmotility is mediated by direct signaling to the enteric nervous system or indirectly via inflammatory macrophages is unknown. METHODS AND RESULTS: We examined these hypotheses by using a clinically relevant permanent intraluminal midcerebral artery occlusion experimental model of stroke. At 24 hours after stroke, we performed in vivo and ex vivo gut motility assays, flow cytometry, immunofluorescence, and transcriptomic analysis. Stroke-induced gut dysmotility was associated with recruitment of muscularis macrophages into the gastrointestinal tract and redistribution of muscularis macrophages away from myenteric ganglia. The permanent intraluminal midcerebral artery occlusion model caused changes in gene expression in muscularis macrophages consistent with an altered phenotype. While the size of myenteric ganglia after stroke was not altered, myenteric neurons from post-permanent intraluminal midcerebral artery occlusion mice showed a reduction in neuronal nitric oxide synthase expression, and this response was associated with enhanced intestinal smooth muscle contraction ex vivo. Finally, chemical sympathectomy with 6-hydroxydopamine prevented the loss of myenteric neuronal nitric oxide synthase expression and stroke-induced slowed gut transit. CONCLUSIONS: Our findings demonstrate that activation of the sympathetic nervous system after stroke is associated with reduced neuronal nitric oxide synthase expression in myenteric neurons, resulting in impaired smooth muscle relaxation and dysregulation of gut transit.

Tenecteplase in Pediatric Stroke: Ready or Not.

BACKGROUND: Intravenous thrombolysis with tissue plasminogen activator is used for off-label treatment of acute childhood stroke. Tenecteplase (TNK) is used to treat acute stroke in adults at many institutions, although there are extremely few data about TNK use in children. We aimed to characterize pediatric stroke experts' experience and preferences with regard to TNK use in children with stroke. METHODS: Online survey distributed to members of the International Pediatric Stroke Organization in April 2023. RESULTS: We received 33 responses. Most (81.2%) respondents reported only being "a little familiar" or "somewhat familiar" with TNK. Only six (18%) respondents reported being "familiar" or "very familiar" with TNK. Seventy percent of respondents were willing to treat pediatric stroke with TNK, at least in some situations. In a hypothetical scenario of a child in an outside emergency room with only TNK available, 81.8% would consider recommending treatment with TNK. However, only three (9.1%) respondents had TNK in their stroke protocol and seven (21.2%) had TNK on formulary at their hospital. Two respondents reported direct awareness of a child treated with TNK. CONCLUSIONS: The majority of pediatric stroke neurologists responding to this survey reported a willingness to consider TNK use in children. However, data on TNK use in children, provider experience, and pediatric hospital preparedness are limited.

Femur Fractures in 5 Individuals With Pantothenate Kinase-associated Neurodegeneration: The Role of Dystonia and Suggested Management.

BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is a rare, neurodegenerative disorder that manifests with progressive loss of ambulation and refractory dystonia, especially in the early-onset classic form. This leads to osteopenia and stress on long bones, which pose an increased risk of atraumatic femur fractures. The purpose of this study is to describe the unique challenges in managing femur fractures in PKAN and the effect of disease manifestations on surgical outcomes. METHODS: A retrospective case review was conducted on 5 patients (ages 10 to 20 y) with PKAN with a femur fracture requiring surgical intervention. Data regarding initial presentation, surgical treatment, complications, and outcomes were obtained. RESULTS: All patients were non-ambulatory, with 4 of 5 patients sustaining an atraumatic femur fracture in the setting of dystonia episode. One patient had an additional contralateral acetabular fracture. Postoperatively, 4 of the 5 patients sustained orthopaedic complications requiring surgical revision, with 3 of these secondary to dystonia. Overall, 4 required prolonged hospitalization in the setting of refractory dystonia. CONCLUSION: Femur fractures in PKAN present distinct challenges for successful outcomes. A rigid intramedullary rod with proximal and distal interlocking screws is most protective against surgical complications associated with refractory dystonia occurring during the postoperative period. Multidisciplinary planning for postoperative care is essential and may include aggressive sedation and pain management to decrease the risk of subsequent injuries or complications. LEVEL OF EVIDENCE: Level IV.

Allelic strengths of encephalopathy-associated UBA5 variants correlate between in vivo and in vitro assays.

Protein UFMylation downstream of the E1 enzyme UBA5 plays essential roles in development and endoplasmic reticulum stress. Variants in the UBA5 gene are associated with developmental and epileptic encephalopathy 44 (DEE44), an autosomal recessive disorder characterized by early-onset encephalopathy, movement abnormalities, global developmental delay, intellectual disability, and seizures. DEE44 is caused by at least 12 different missense variants described as loss of function (LoF), but the relationships between genotypes and molecular or clinical phenotypes remain to be established. We developed a humanized UBA5 fly model and biochemical activity assays in order to describe in vivo and in vitro genotype-phenotype relationships across the UBA5 allelic series. In vivo, we observed a broad spectrum of phenotypes in viability, developmental timing, lifespan, locomotor activity, and bang sensitivity. A range of functional effects was also observed in vitro across comprehensive biochemical assays for protein stability, ATP binding, UFM1 activation, and UFM1 transthiolation. Importantly, there is a strong correlation between in vivo and in vitro phenotypes, establishing a classification of LoF variants into mild, intermediate, and severe allelic strengths. By systemically evaluating UBA5 variants across in vivo and in vitro platforms, this study provides a foundation for more basic and translational UBA5 research, as well as a basis for evaluating current and future individuals afflicted with this rare disease.

Although rare diseases only impact a small fraction of the population, they still affect hundreds of millions of people around the world. Many of these conditions are caused by variations in inherited genetic material, which nowadays can be readily detected using advanced sequencing technologies. However, establishing a connection between these genetic changes and the disease they cause often requires further in-depth study. One such rare inherited disorder is developmental and epileptic encephalopathy type 44 (DEE44), which is caused by genetic variations within the gene for UBA5 (short for ubiquitin-like modifier activating enzyme 5). For DEE44 to occur, both copies of the gene for UBA5, known as alleles, must contain one or more detrimental variation. Although all these variations prevent UBA5 from working correctly, the level of disruption they cause, known as allelic strength, varies between them. However, it remained unclear whether the severity of the DEE44 disease directly corresponds with the allelic strength of these variants. To answer this question, Pan et al. tested how different genetic variants found in patients with DEE44 affected the behavior and health of fruit flies. These results were then compared against in vitro biochemical assays testing how alleles containing these variants impacted the function of UBA5. When the fly gene for the enzyme was replaced with the human gene containing variations associated with DEE44, flies exhibited changes in their survival rates, developmental progress, lifespan, and neurological well-being. However, not all of the variants caused ill effects. Using this information, the patient variants were classified into three categories based on the severity of their effect: mild, intermediate, and severe. Biochemical assays supported this classification and revealed that the variants that caused more severe symptoms tended to inhibit the activity of UBA5 more significantly. Pan et al. further analyzed the nature of the variants in the patients and showed that most patients typically carried one mild and one strong variant, although some individuals did have two intermediate variants. Notably, no patients carried two severe variants. This indicates that DEE44 is the result of UBA5 only partially losing its ability to work correctly. The study by Pan et al. provides a framework for assessing the impact of genetic variants associated with DEE44, aiding the diagnosis and treatment of the disorder. However, further research involving more patients, more detailed clinical data, and testing other newly identified DEE44-causing variants is needed to solidify the correlation between allelic strength and disease severity.

Sympathetic-Mediated Intestinal Cell Death Contributes to Gut Barrier Impairment After Stroke.

Tissue injury induced by stroke is traditionally thought to be localised to the brain. However, there is an accumulating body of evidence to demonstrate that stroke promotes pathophysiological consequences in peripheral tissues including the gastrointestinal system. In this study, we investigated the mechanisms underlying gut permeability after stroke. We utilised the clinically relevant experimental model of stroke called permanent intraluminal middle cerebral artery occlusion (pMCAO) to examine the effect of cerebral ischaemia on the gut. We detected stroke-induced gut permeability at 5 h after pMCAO. At this timepoint, we observed significantly elevated intestinal epithelial cell death in post-stroke mice compared to their sham-operated counterparts. At 24 h after stroke onset when the gut barrier integrity is restored, our findings indicated that post-stroke intestinal epithelium had higher expression of genes associated with fructose metabolism, and hyperplasia of intestinal crypts and goblet cells, conceivably as a host compensatory mechanism to adapt to the impaired gut barrier. Furthermore, we discovered that stroke-induced gut permeability was mediated by the activation of the sympathetic nervous system as pharmacological denervation decreased the stroke-induced intestinal epithelial cell death, goblet cell and crypt hyperplasia, and gut permeability to baseline levels. Our study identifies a previously unknown mechanism in the brain-gut axis by which stroke triggers intestinal cell death and gut permeability.

SIGnature Libraries: A roadmap for the formation of special interest group libraries.

Objective: "SIGnature Libraries" channel the dynamism of academic society-based special interest groups (SIG) to systematically identify and provide user-oriented access to essential literature for a subspecialty field in a manner that keeps pace with the field's continuing evolution. The libraries include literature beyond clinical trial data to encompass historical context, diagnostic conceptualization, and community organization materials to foster a holistic understanding of how neurologic conditions affect individuals, their community, and their lived experience. Methods: Utilizing a modified-Delphi approach, Child Neurology Society's Cerebral Palsy (CP) SIG (n = 75) administered two rounds of literature submissions and ratings. A final review by an 11-member international advisory group determined threshold ratings for resource inclusion and the library's final structure. Results: Seventy-nine articles were submitted for the first Delphi round and 22 articles for the second Delphi round. Survey response rates among SIG members were 29/75 for the first round and 24/75 for the second round. The advisory board added additional articles in the final review process in view of the overall project goal. A total of 60 articles were included in the final library, and articles were divided into seven sections and stratified by rating scores. A process for ongoing revisions of the library was determined. The library will be published on the Child Neurology Society website and made publicly accessible. Conclusions: The CP SIGnature Library offers learners an unprecedented resource that provides equitable access to latest consensus guidelines, existing seminal datasets, up-to-date review articles, and other patient care tools. A distinctive feature of the library is its intentional large scope and depth, presented in a stratified fashion relative to the consensus-determined importance of each article. Learners can efficiently navigate the library based on individual interests and goals, and the library can be used as core curriculum for CP education.

Allelic strengths of encephalopathy-associated UBA5 variants correlate between in vivo and in vitro assays.

Protein UFMylation downstream of the E1 enzyme UBA5 plays essential roles in development and ER stress. Variants in the UBA5 gene are associated with developmental and epileptic encephalopathy 44 (DEE44), an autosomal recessive disorder characterized by early-onset encephalopathy, movement abnormalities, global developmental delay, intellectual disability, and seizures. DEE44 is caused by at least twelve different missense variants described as loss of function (LoF), but the relationships between genotypes and molecular or clinical phenotypes remains to be established. We developed a humanized UBA5 fly model and biochemical activity assays in order to describe in vivo and in vitro genotype-phenotype relationships across the UBA5 allelic series. In vivo, we observed a broad spectrum of phenotypes in viability, developmental timing, lifespan, locomotor activity, and bang sensitivity. A range of functional effects was also observed in vitro across comprehensive biochemical assays for protein stability, ATP binding, UFM1 activation, and UFM1 transthiolation. Importantly, there is a strong correlation between in vivo and in vitro phenotypes, establishing a classification of LoF variants into mild, intermediate, and severe allelic strengths. By systemically evaluating UBA5 variants across in vivo and in vitro platforms, this study provides a foundation for more basic and translational UBA5 research, as well as a basis for evaluating current and future individuals afflicted with this rare disease.

Tenecteplase in Acute Stroke: What About the Children?

Tenecteplase is replacing alteplase as the fibrinolytic agent of choice for the acute management of ischemic stroke in many adult stroke centers due to practical and pharmacokinetic advantages in the setting of similar outcomes. Although thrombolytic use is increasing for acute childhood stroke, there is very limited experience with tenecteplase in children for any indication, and importantly, there are no data on safety, dosing, or efficacy of tenecteplase for childhood stroke. Changes in fibrinolytic capacity over childhood, pediatric pharmacological considerations such as age-specific differences in drug clearance and volume of distribution, and practical aspects of drug delivery such as availability in children's hospitals may impact decisions about transitioning from alteplase to tenecteplase for acute pediatric stroke treatment. Pediatric and adult neurologists should prepare institution-specific guidelines and organize prospective data collection.

The Role of Child Neurologists in the Management of Motor Disability in Cerebral Palsy: Establishing the Path Forward.

BACKGROUND: Cerebral palsy (CP) is the most common motor disability of childhood, and yet the role of child neurologists and neurodevelopmentalists (CN/NDDs) in the management of children with CP is unclear. Although previous surveys showed that CN/NDDs believe they are uniquely expert in CP motor phenotyping and should be involved in CP management, others have demonstrated that training in CP management among CN/NDD residency programs is inadequate. METHODS: In this article, we surveyed a group of CN/NDDs at the Child Neurology Society Cerebral Palsy Special Interest Group meeting on January 27, 2022. Questions addressed provider comfort with CP tone management including motor phenotyping, pharmacologic and surgical management, barriers and solutions to improving practice, and the use of systems-based care. RESULTS: Responses from 42 participants demonstrated that CN/NDDs lack experience with CP tone management, with 48% and 58% of respondents reporting little to no experience in pharmacologic or surgical management, respectively. Primary barriers identified to improving comfort with CP tone management included lack of knowledge and ineffective treatment options, while most solutions centered on improving collaborations between CN/NDDs and other specialties. Only 50% of respondents reported currently using systems-based care in the management of patients with CP. CONCLUSIONS: An interdisciplinary, systems-based care model would allow for collaboration and knowledge sharing between involved specialties and provide high-value goal-directed care to maximize the functional outcomes for every individual with CP.

Abnormal Brain Iron Accumulation is a Rare Finding in Down Syndrome Regression Disorder.

BACKGROUND: Down syndrome regression disorder (DSRD) is characterized by the sudden loss of adaptive function, cognitive-executive function, and language with abnormal sleep and/or motor control. METHODS: Clinical, laboratory, and imaging data from three individuals with DSRD and iron on brain imaging were reviewed. RESULTS: Three patients with Down syndrome presented with new onset of flat affect, depression, reduced speech, and other neurological symptoms consistent with DSRD. Magnetic resonance imaging showed abnormal iron accumulation in the basal ganglia, as well as calcification in two cases. Molecular diagnostic testing for neurodegeneration with brain iron accumulation was negative in the two individuals tested. CONCLUSIONS: These individuals presented suggest that a subset of individuals with DSRD have abnormal brain iron accumulation. Motor control symptoms reported in DSRD, such as stereotypies and parkinsonism, may reflect this basal ganglia involvement. The presence of abnormal brain iron should not delay or preclude diagnosis and treatment for DSRD.

What state of the world are we in? Targeted monitoring to detect transitions in vegetation restoration projects.

Monitoring vegetation restoration is challenging because monitoring is costly, requires long-term funding, and involves monitoring multiple vegetation variables that are often not linked back to learning about progress toward objectives. There is a clear need for the development of targeted monitoring programs that focus on a reduced set of variables that are tied to specific restoration objectives. In this paper, we present a method to progress the development of a targeted monitoring program, using a pre-existing state-and-transition model. We (1) use field data to validate an expert-derived classification of woodland vegetation states; (2) use these data to identify which variable(s) help differentiate woodland states; and (3) identify the target threshold (for the variable) that signifies if the desired transition has been achieved. The measured vegetation variables from each site in this study were good predictors of the different states. We show that by measuring only a few of these variables, it is possible to assign the vegetation state for a collection of sites, and monitor if and when a transition to another state has occurred. For this ecosystem and state-and-transition models, out of nine vegetation variables considered, the density of immature trees and percentage of exotic understory vegetation cover were the variables most frequently specified as effective to define a threshold or transition. We synthesize findings by presenting a decision tree that provides practical guidance for the development of targeted monitoring strategies for woodland vegetation.

Adolescent Mental Health Priorities During the Covid-19 Pandemic.

Increasing evidence has shown that the Covid-19 outbreak has impacted adolescents' mental health. Utilising a mixed-method design, the current study examined a total of 518 adolescent perspectives (60% female), in Scotland, on what has and could help their mental health in the context of Covid-19. A reflexive thematic analysis revealed three themes in relation to what has helped adolescents' mental health since the Covid-19 outbreak. These related to findings about the value of: (1) engaging in recreational activities, (2) engaging with friends, and (3) the disruption to schooling. The remaining four themes related to what could have helped adolescents mental health and wellbeing since the Covid-19 outbreak. These focussed on (1) better support: in relation to mental health; school work; and communication, (2) contact with friends, and (3) more opportunities for recreational activities. Males were more likely to report recreational activities had helped and less likely to report better support could have helped. Adolescents who reached clinical threshold for depression and anxiety and those with elevated PTSD-like symptoms about Covid-19 were more likely to state more support could have helped, and adolescents who reached clinical threshold for depression were less likely to report that friends could have helped their mental health. The findings may inform mental health policy and interventions in the recovery from the Covid-19 pandemic.

Brain-associated innate leukocytes display diverse inflammatory states following experimental stroke.

Previous studies investigating innate leukocyte recruitment into the brain after cerebral ischemia have shown conflicting results. Using distinct cell surface and intracellular markers, the current study evaluated the contributions of innate immune cells to the poststroke brain following 1-h middle cerebral artery occlusion (tMCAO) or permanent MCAO (pMCAO), and assessed whether these cells ascribed to an inflammatory state. Moreover, we examined whether there is evidence for leukocyte infiltration into the contralateral (CL) hemisphere despite the absence of stroke infarct. We observed the recruitment of peripheral neutrophils, monocytes and macrophages into the hemisphere ipsilateral (IL) to the ischemic brain infarct at 24 and 96 h following both tMCAO and pMCAO. In addition, we found evidence of increased leukocyte recruitment to the CL hemisphere but to a lesser extent than the IL hemisphere after stroke. Robust production of intracellular cytokines in the innate immune cell types examined was most evident at 24 h after pMCAO. Specifically, brain-associated neutrophils, monocytes and macrophages demonstrated stroke-induced production of tumor necrosis factor-α (TNF-α) and interleukin (IL)-1ß, while only monocytes and macrophages exhibit a significant expression of arginase 1 (Arg1) after stroke. At 96 h after stroke, brain-resident microglia demonstrated production of TNF-α and IL-1ß following both tMCAO and pMCAO. At this later timepoint, neutrophils displayed TNF-α production and brain-associated macrophages exhibited elevation of IL-1ß and Arg1 after tMCAO. Further, pMCAO induced significant expression of Arg1 and IL-1ß in monocytes and macrophages at 96 h, respectively. These results revealed that brain-associated innate immune cells display various stroke-induced inflammatory states that are dependent on the experimental stroke setting.

Pediatric Stroke due to Thoracic Outlet Syndrome Treated with Thrombolysis and Thrombectomy: A Case Report.

Thoracic outlet syndrome (TOS) is a condition that results from the compression of neurovascular structures as they exit the thorax. Arterial ischemic stroke can occur in TOS due to retrograde embolism from the subclavian artery. We describe a 15-year-old girl who presented with left hemiplegia after 2 weeks of right arm numbness and tingling. Imaging showed an acute ischemic stroke due to a right middle cerebral artery occlusion. She was treated with intravenous tissue plasminogen activator at 1.3 h and mechanical thrombectomy at 2.4 h with successful recanalization. Review of her neck computed tomography angiogram suggested a right subclavian artery aneurysm, and upper-extremity imaging also demonstrated distal thrombosis and fusion of right first and second ribs, which was consistent with thoracic outlet syndrome. Three days later, she underwent a right subclavian artery aneurysm repair, right brachial and ulnar artery thrombectomy, and first rib resection. Three months later, she demonstrated good neurologic recovery. TOS is an uncommon cause of stroke in children, which may be heralded by upper-extremity symptoms. Interventionalists should be aware of the possibility of vascular anomalies in children; however, this finding does not exclude the possibility of acute stroke intervention.

Diagnosis and Initial Treatment of Functional Movement Disorders in Children.

Functional movement disorders (FMD) are complex neurobehavioral disorders that can be a significant source of disability for both children and their caregivers. While FMD in the adult population is better characterized, the aim of this paper is to review the pertinent clinical and historical features, diagnostic criteria, and multi-disciplinary management of FMD in the pediatric population. We highlight recent trends in pediatric FMD, including the increase in functional tic-like behaviors that has been observed during the COVID-19 pandemic.

Lung Imaging Reveals Stroke-Induced Impairment in Pulmonary Intravascular Neutrophil Function, a Response Exacerbated with Aging.

In stroke patients, infection is a significant contributor to morbidity and mortality. Moreover, older stroke patients show an increased risk of developing stroke-associated infection, although the mechanisms underlying this increased susceptibility to infection are unknown. In this study, using an experimental mouse model of ischemic stroke, we showed that older (12-15 mo of age) mice had elevated lung bacterial infection and inflammatory damage after stroke when compared with young (8-10 wk of age) counterparts, despite undergoing the same degree of brain injury. Intravital microscopy of the lung microvasculature revealed that in younger mice, stroke promoted neutrophil arrest in pulmonary microvessels, but this response was not seen in older poststroke mice. In addition, bacterial phagocytosis by neutrophils in the lung microvasculature was reduced by both aging and stroke, such that neutrophils in aged poststroke mice showed the greatest impairment in this function. Analysis of neutrophil migration in vitro and in the cremaster muscle demonstrated that stroke alone did not negatively impact neutrophil migration, but that the combination of increased age and stroke led to reduced effectiveness of neutrophil chemotaxis. Transcriptomic analysis of pulmonary neutrophils using RNA sequencing identified 79 genes that were selectively altered in the context of combined aging and stroke, and they were associated with pathways that control neutrophil chemotaxis. Taken together, the findings of this study show that stroke in older animals results in worsening of neutrophil antibacterial responses and changes in neutrophil gene expression that have the potential to underpin elevated risk of stroke-associated infection in the context of increased age.