Macroscopic changes in aquaporin-4 underlie blast traumatic brain injury-related impairment in glymphatic function.

Mild traumatic brain injury (mTBI) has emerged as a potential risk factor for the development of neurodegenerative conditions such as Alzheimer's disease and chronic traumatic encephalopathy. Blast mTBI, caused by exposure to a pressure wave from an explosion, is predominantly experienced by military personnel and has increased in prevalence and severity in recent decades. Yet the underlying pathology of blast mTBI is largely unknown. We examined the expression and localization of AQP4 in human post-mortem frontal cortex and observed distinct laminar differences in AQP4 expression following blast exposure. We also observed similar laminar changes in AQP4 expression and localization and delayed impairment of glymphatic function that emerged 28 days following blast injury in a mouse model of repetitive blast mTBI. In a cohort of veterans with blast mTBI, we observed that blast exposure was associated with an increased burden of frontal cortical MRI-visible perivascular spaces, a putative neuroimaging marker of glymphatic perivascular dysfunction. These findings suggest that changes in AQP4 and delayed glymphatic impairment following blast injury may render the post-traumatic brain vulnerable to post-concussive symptoms and chronic neurodegeneration.

Dynamic changes in perivascular space morphology predict signs of spaceflight-associated neuro-ocular syndrome in bed rest.

During long-duration spaceflight, astronauts experience headward fluid shifts and expansion of the cerebral perivascular spaces (PVS). A major limitation to our understanding of the changes in brain structure and physiology induced by spaceflight stems from the logistical difficulties of studying astronauts. The current study aimed to determine whether PVS changes also occur on Earth with the spaceflight analog head-down tilt bed rest (HDBR). We examined how the number and morphology of magnetic resonance imaging-visible PVS (MV-PVS) are affected by HDBR with and without elevated carbon dioxide (CO2). These environments mimic the headward fluid shifts, body unloading, and elevated CO2 observed aboard the International Space Station. Additionally, we sought to understand how changes in MV-PVS are associated with signs of Spaceflight Associated Neuro-ocular Syndrome (SANS), ocular structural alterations that can occur with spaceflight. Participants were separated into two bed rest campaigns: HDBR (60 days) and HDBR + CO2 (30 days with elevated ambient CO2). Both groups completed multiple magnetic resonance image acquisitions before, during, and post-bed rest. We found that at the group level, neither spaceflight analog affected MV-PVS quantity or morphology. However, when taking into account SANS status, persons exhibiting signs of SANS showed little or no MV-PVS changes, whereas their No-SANS counterparts showed MV-PVS morphological changes during the HDBR + CO2 campaign. These findings highlight spaceflight analogs as models for inducing changes in MV-PVS and implicate MV-PVS dynamic compliance as a mechanism underlying SANS. These findings may lead to countermeasures to mitigate health risks associated with human spaceflight.

Perivascular Space Burden and Cerebrospinal Fluid Biomarkers in US Veterans With Blast-Related Mild Traumatic Brain Injury.

Blast-related mild traumatic brain injury (mTBI) is recognized as the "signature injury" of the Iraq and Afghanistan wars. Sleep disruption, mTBI, and neuroinflammation have been individually linked to cerebral perivascular space (PVS) dilatation. Dilated PVSs are putative markers of impaired cerebrospinal fluid (CSF) and interstitial fluid exchange, which plays an important role in removing cerebral waste. The aim of this cross-sectional, retrospective study was to define associations between biomarkers of inflammation and MRI-visible PVS (MV-PVS) burden in Veterans after blast-related mTBI (blast-mTBI) and controls. The CSF and plasma inflammatory biomarker concentrations were compared between blast-mTBI and control groups and correlated with MV-PVS volume and number per white matter cm3. Multiple regression analyses were performed with inflammatory biomarkers as predictors and MV-PVS burden as the outcome. Correction for multiple comparisons was performed using the Banjamini-Hochberg method with a false discovery rate of 0.05. There were no group-wise differences in MV-PVS burden between Veterans with blast-mTBI and controls. Greater MV-PVS burden was significantly associated with higher concentrations of several proinflammatory biomarkers from CSF (i.e., eotaxin, MCP-1, IL-6, IL-8) and plasma (i.e., MCP-4, IL-13) in the blast-mTBI group only. After controlling for sleep time and symptoms of post-traumatic stress disorder, temporal MV-PVS burden remained significantly associated with higher CSF markers of inflammation in the blast-mTBI group only. These data support an association between central, rather than peripheral, neuroinflammation and MV-PVS burden in Veterans with blast-mTBI independent of sleep. Future studies should continue to explore the role of blast-mTBI related central inflammation in MV-PVS development, as well as investigate the impact of subclinical exposures on MV-PVS burden.

Manejo del estado epiléptico en niños: encuesta en hospitales pediátricos de la Ciudad Autónoma de Buenos Aires / Management of status epilepticus in childhood: a survey conducted at pediatric hospitals in the City of Buenos Aires

Introducción. El estado epiléptico constituye la emergencia neurológica más frecuente. Si bien la mortalidad en niños es baja, su morbilidad puede superar el 20 %. Objetivo. Conocer las pautas de manejo del estado epiléptico referidas por médicos pediatras que atienden esta patología en forma habitual. Población y métodos. Estudio descriptivo, transversal, basado en una encuesta a médicos de tres hospitales pediátricos monovalentes de gestión pública de la Ciudad Autónoma de Buenos Aires. Resultados. Se administraron 292 encuestas (la tasa de respuesta completa alcanzó el 86 %); el 77 % se administró a pediatras y el 16 %, a especialistas en cuidados intensivos. Un 47 % de los participantes refiere indicar la primera benzodiacepina en el tiempo correcto; el 56 % utilizar diazepam intrarrectal en ausencia de un acceso intravenoso; el 95 % elige lorazepam como benzodiacepina inicial en caso de contar con acceso intravenoso; el 58 % refiere iniciar la etapa de fármacos de segunda línea en tiempo adecuado; el 84 % opta por fenitoína como fármaco inicial de segunda línea, un 33 % no cronometra el tiempo durante el tratamiento. La adherencia global a las recomendaciones internacionales fue del 17 %. Conclusiones. Nuestro estudio advierte una baja adherencia referida de los pediatras a las guías internacionales, en particular en las decisiones tiempo-dependientes. También se observó mayor heterogeneidad en las conductas terapéuticas a medida que se avanza en el algoritmo de tratamiento.

Introduction. Status epilepticus is the most common neurological emergency. Although mortality in children is low, morbidity may exceed 20%. Objective. To evaluate the management of status epilepticus by pediatricians who usually treat this condition. Population and methods. Descriptive, cross-sectional study based on a survey administered to physicians from 3 pediatric hospitals in the City of Buenos Aires. Results. A total of 292 surveys were administered (complete response rate as high as 86%); 77% were administered to pediatricians and 16% to intensive care specialists. Forty-seven percent of the participants reported that they administer the first dose of a benzodiazepine within the correct timeframe; 56% use intrarectal diazepam when intravenous access is not available; 95% choose lorazepam as the initial benzodiazepine if an intravenous access is available; 58% initiate the administration of a second-line drug within the correct timeframe; 84% administer phenytoin as the first-choice, second-line drug; and 33% do not measure treatment time. Overall adherence to international recommendations was 17%. Conclusions. Our study highlights poor adherence of pediatricians to international guidelines, particularly in time-dependent decisions. Greater heterogeneity was observed in treatment approaches as the treatment algorithm progressed.