Kinetics of Hepatitis E Virus Infections in Asymptomatic Persons.

To determine the kinetics of hepatitis E virus (HEV) in asymptomatic persons and to evaluate viral load doubling time and half-life, we retrospectively tested samples retained from 32 HEV RNA-positive asymptomatic blood donors in Germany. Close-meshed monitoring of viral load and seroconversion in intervals of ≈4 days provided more information about the kinetics of asymptomatic HEV infections. We determined that a typical median infection began with PCR-detectable viremia at 36 days and a maximum viral load of 2.0 × 104 IU/mL. Viremia doubled in 2.4 days and had a half-life of 1.6 days. HEV IgM started to rise on about day 33 and peaked on day 36; IgG started to rise on about day 32 and peaked on day 53. Although HEV IgG titers remained stable, IgM titers became undetectable in 40% of donors. Knowledge of the dynamics of HEV viremia is useful for assessing the risk for transfusion-transmitted hepatitis E.

Prevalence and characteristics of rapid eye movement sleep behaviour disorder in adults with migraine: a cross-sectional screening study.

BACKGROUND AND PURPOSE: Migraine and sleep disorders share a bidirectional relationship, but little is known about the specific association between migraine and rapid eye movement (REM) sleep behaviour disorder (RBD). The aim was to assess the prevalence of RBD and associated clinical characteristics in adults with migraine. METHODS: This analysis is part of a cross-sectional survey study conducted at the Headache Centre of the Charité-Universitätsmedizin Berlin between August 2020 and March 2023. At the end of their regular medical consultation, patients with migraine filled out (1) the validated RBD Screening Questionnaire (RBDSQ), (2) a questionnaire on REM sleep intrusions and (3) the Depression, Anxiety and Stress Scale 21. The primary endpoint was the percentage of patients with a positive RBD screening. A multivariate analysis was performed to identify characteristics independently associated with features of RBD. RESULTS: A total of 751 patients (44.1 ± 13.2 years; 87.4% female) with complete RBDSQ were included in this analysis, of which 443 (58.9%) screened positive for RBD. In multivariate analysis, a positive screening for RBD was associated with younger age (odds ratio [OR] 0.9, 95% confidence interval [CI] 0.8-0.9 per 10-year increase; p = 0.005) and with features suggestive of REM sleep intrusions (OR 4.3, 95% CI 1.8-10.4; p = 0.001). Migraine aura remained in the model without reaching statistical significance (OR 1.3, 95% CI 0.9-1.8; p = 0.079). DISCUSSION: Symptoms of RBD are frequent in adults with migraine. Further studies including polysomnography are required to confirm this association, and to explore potential common pathophysiological mechanisms.

Hepatitis E virus infections in German blood donors: results of 8 years of screening, 2015 to 2022.

BackgroundAwareness of transfusion-transmitted hepatitis E raised in recent years led to the mandatory testing of blood donations in some European countries for hepatitis E virus (HEV) RNA. However, little is known about the epidemiology of HEV infections.AimTo and describe and analyse the epidemiology of HEV infections in blood donors in Germany.MethodsData from routine testing of therapeutic blood products donated between January 2015 and December 2022 at the Uni.Blutspendedienst OWL were analysed at the Institute of Laboratory and Transfusion Medicine, Heart and Diabetes Centre North Rhine-Westphalia. A total of 731,630 allogenic blood donations from 119,610 individual blood donors were tested for HEV RNA in minipools of 96 samples. The HEV RNA-positive donations were analysed for the presence of anti-HEV IgM and IgG. The HEV strains were genotyped and various clinical liver-specific parameters were determined.ResultsA total of 497 HEV-positive blood donations were identified, resulting in a yearly incidence of 1:1,474, from which 78.4% of the donations were RNA-only positive. Increased alanine aminotransferase activity was determined in 26.6% of HEV RNA-positive donors and was associated with the detection of IgG antibodies (1.2% anti-HEV IgM-positive, 11.9% anti-HEV IgM- and IgG-positive and 8.5% anti-HEV IgG-positive). An average incidence of 0.084-0.083% HEV RNA-positive donations in June and July in all years was observed, and a higher proportion of HEV RNA-positive men compared with women. All isolated HEV sequences corresponded to genotype 3.ConclusionOur results underline the necessity of HEV RNA screening in blood donations.

Prediction of Stroke Outcome in Mice Based on Noninvasive MRI and Behavioral Testing.

BACKGROUND: Prediction of poststroke outcome using the degree of subacute deficit or magnetic resonance imaging is well studied in humans. While mice are the most commonly used animals in preclinical stroke research, systematic analysis of outcome predictors is lacking. METHODS: We intended to incorporate heterogeneity into our retrospective study to broaden the applicability of our findings and prediction tools. We therefore analyzed the effect of 30, 45, and 60 minutes of arterial occlusion on the variance of stroke volumes. Next, we built a heterogeneous cohort of 215 mice using data from 15 studies that included 45 minutes of middle cerebral artery occlusion and various genotypes. Motor function was measured using a modified protocol for the staircase test of skilled reaching. Phases of subacute and residual deficit were defined. Magnetic resonance images of stroke lesions were coregistered on the Allen Mouse Brain Atlas to characterize stroke topology. Different random forest prediction models that either used motor-functional deficit or imaging parameters were generated for the subacute and residual deficits. RESULTS: Variance of stroke volumes was increased by 45 minutes of arterial occlusion compared with 60 minutes. The inclusion of various genotypes enhanced heterogeneity further. We detected both a subacute and residual motor-functional deficit after stroke in mice and different recovery trajectories could be observed. In mice with small cortical lesions, lesion volume was the best predictor of the subacute deficit. The residual deficit could be predicted most accurately by the degree of the subacute deficit. When using imaging parameters for the prediction of the residual deficit, including information about the lesion topology increased prediction accuracy. A subset of anatomic regions within the ischemic lesion had particular impact on the prediction of long-term outcomes. Prediction accuracy depended on the degree of functional impairment. CONCLUSIONS: For the first time, we developed and validated a robust tool for the prediction of functional outcomes after experimental stroke in mice using a large and genetically heterogeneous cohort. These results are discussed in light of study design and imaging limitations. In the future, using outcome prediction can improve the design of preclinical studies and guide intervention decisions.

Deep Isoflurane Anesthesia Is Associated with Alterations in Ion Homeostasis and Specific Na+/K+-ATPase Impairment in the Rat Brain.

BACKGROUND: Maintenance of ion homeostasis is essential for normal brain function. Inhalational anesthetics are known to act on various receptors, but their effects on ion homeostatic systems, such as sodium/potassium-adenosine triphosphatase (Na+/K+-ATPase), remain largely unexplored. Based on reports demonstrating global network activity and wakefulness modulation by interstitial ions, the hypothesis was that deep isoflurane anesthesia affects ion homeostasis and the key mechanism for clearing extracellular potassium, Na+/K+-ATPase. METHODS: Using ion-selective microelectrodes, this study assessed isoflurane-induced extracellular ion dynamics in cortical slices of male and female Wistar rats in the absence of synaptic activity, in the presence of two-pore-domain potassium channel antagonists, during seizures, and during spreading depolarizations. The specific isoflurane effects on Na+/K+-ATPase function were measured using a coupled enzyme assay and studied the relevance of the findings in vivo and in silico. RESULTS: Isoflurane concentrations clinically relevant for burst suppression anesthesia increased baseline extracellular potassium (mean ± SD, 3.0 ± 0.0 vs. 3.9 ± 0.5 mM; P < 0.001; n = 39) and lowered extracellular sodium (153.4 ± 0.8 vs. 145.2 ± 6.0 mM; P < 0.001; n = 28). Similar changes in extracellular potassium and extracellular sodium and a substantial drop in extracellular calcium (1.5 ± 0.0 vs. 1.2 ± 0.1 mM; P = 0.001; n = 16) during inhibition of synaptic activity and two-pore-domain potassium suggested a different underlying mechanism. After seizure-like events and spreading depolarization, isoflurane greatly slowed extracellular potassium clearance (63.4 ± 18.2 vs. 196.2 ± 82.4 s; P < 0.001; n = 14). Na+/K+-ATPase activity was markedly reduced after isoflurane exposure (greater than 25%), affecting specifically the α2/3 activity fraction. In vivo, isoflurane-induced burst suppression resulted in impaired extracellular potassium clearance and interstitial potassium accumulation. A computational biophysical model reproduced the observed effects on extracellular potassium and displayed intensified bursting when Na+/K+-ATPase activity was reduced by 35%. Finally, Na+/K+-ATPase inhibition with ouabain induced burst-like activity during light anesthesia in vivo. CONCLUSIONS: The results demonstrate cortical ion homeostasis perturbation and specific Na+/K+-ATPase impairment during deep isoflurane anesthesia. Slowed potassium clearance and extracellular accumulation might modulate cortical excitability during burst suppression generation, while prolonged Na+/K+-ATPase impairment could contribute to neuronal dysfunction after deep anesthesia.

Near-death experiences are associated with rapid eye movement (REM) sleep intrusions in migraine patients, independent of migraine aura.

BACKGROUND AND PURPOSE: Migraine aura, near-death experiences (NDEs), and rapid eye movement (REM) sleep intrusions might share common mechanisms. Here, we investigated the prevalence of NDEs and REM sleep intrusions in people with migraine. We hypothesized that NDEs and REM sleep intrusions are more prevalent in migraine patients with aura than in those without. METHODS: We conducted a prospective cross-sectional cohort study at a tertiary headache center, based on a prespecified sample size (n = 808). Migraine patients completed a series of questionnaires, including questions about demographic and headache characteristics, the 16-item Greyson NDE scale, four questions about REM sleep intrusions, and the Depression, Anxiety, and Stress Scale 21 (DASS-21). RESULTS: Of 808 migraine patients (mean age 44.4 ± 13.3 years, 87.0% women), 353 (43.7%) had a current or previous history of migraine aura. Prevalence of NDE was 2.7% and not different in patients with and without aura (2.8% vs. 2.6%; p > 0.999). REM sleep intrusions were reported by 5.4% of participants and in a similar proportion of patients with and without aura (6.3% vs. 4.9%; p = 0.43). However, participants with REM sleep intrusions had had an NDE more often than participants without REM sleep intrusions (n = 5/44, 11.4% vs. n = 17/754, 2.2%; p = 0.005). Higher DASS-21 scores were associated with REM sleep intrusions (p < 0.001). CONCLUSIONS: In this tertiary center cohort study, the prevalence of NDE and REM sleep intrusions was not influenced by migraine aura status. However, we identified an association between NDE and REM sleep intrusions, which corroborates the notion that they might share pathophysiological mechanisms.

Spreading depolarizations in ischaemia after subarachnoid haemorrhage, a diagnostic phase III study.

Focal brain damage after aneurysmal subarachnoid haemorrhage predominantly results from intracerebral haemorrhage, and early and delayed cerebral ischaemia. The prospective, observational, multicentre, cohort, diagnostic phase III trial, DISCHARGE-1, primarily investigated whether the peak total spreading depolarization-induced depression duration of a recording day during delayed neuromonitoring (delayed depression duration) indicates delayed ipsilateral infarction. Consecutive patients (n = 205) who required neurosurgery were enrolled in six university hospitals from September 2009 to April 2018. Subdural electrodes for electrocorticography were implanted. Participants were excluded on the basis of exclusion criteria, technical problems in data quality, missing neuroimages or patient withdrawal (n = 25). Evaluators were blinded to other measures. Longitudinal MRI, and CT studies if clinically indicated, revealed that 162/180 patients developed focal brain damage during the first 2 weeks. During 4.5 years of cumulative recording, 6777 spreading depolarizations occurred in 161/180 patients and 238 electrographic seizures in 14/180. Ten patients died early; 90/170 developed delayed infarction ipsilateral to the electrodes. Primary objective was to investigate whether a 60-min delayed depression duration cut-off in a 24-h window predicts delayed infarction with >0.60 sensitivity and >0.80 specificity, and to estimate a new cut-off. The 60-min cut-off was too short. Sensitivity was sufficient [= 0.76 (95% confidence interval: 0.65-0.84), P = 0.0014] but specificity was 0.59 (0.47-0.70), i.e. <0.80 (P < 0.0001). Nevertheless, the area under the receiver operating characteristic (AUROC) curve of delayed depression duration was 0.76 (0.69-0.83, P < 0.0001) for delayed infarction and 0.88 (0.81-0.94, P < 0.0001) for delayed ischaemia (reversible delayed neurological deficit or infarction). In secondary analysis, a new 180-min cut-off indicated delayed infarction with a targeted 0.62 sensitivity and 0.83 specificity. In awake patients, the AUROC curve of delayed depression duration was 0.84 (0.70-0.97, P = 0.001) and the prespecified 60-min cut-off showed 0.71 sensitivity and 0.82 specificity for reversible neurological deficits. In multivariate analysis, delayed depression duration (ß = 0.474, P < 0.001), delayed median Glasgow Coma Score (ß = -0.201, P = 0.005) and peak transcranial Doppler (ß = 0.169, P = 0.016) explained 35% of variance in delayed infarction. Another key finding was that spreading depolarization-variables were included in every multiple regression model of early, delayed and total brain damage, patient outcome and death, strongly suggesting that they are an independent biomarker of progressive brain injury. While the 60-min cut-off of cumulative depression in a 24-h window indicated reversible delayed neurological deficit, only a 180-min cut-off indicated new infarction with >0.60 sensitivity and >0.80 specificity. Although spontaneous resolution of the neurological deficit is still possible, we recommend initiating rescue treatment at the 60-min rather than the 180-min cut-off if progression of injury to infarction is to be prevented.

Cerebrovascular Pressure Reactivity According to Long-Pressure Reactivity Index During Spreading Depolarizations in Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND: Spreading depolarization (SD) has been linked to the impairment of neurovascular coupling. However, the association between SD occurrence and cerebrovascular pressure reactivity as a surrogate of cerebral autoregulation (CA) remains unclear. Therefore, we analyzed CA using the long-pressure reactivity index (L-PRx) during SDs in patients with aneurysmal subarachnoid hemorrhage (aSAH). METHODS: A retrospective study of patients with aSAH who were recruited at two centers, Heidelberg (HD) and Berlin (BE), was performed. Continuous monitoring of mean arterial pressure (MAP) and intracranial pressure (ICP) was recorded. ICP was measured using an intraparenchymal probe in HD patients and was measure in BE patients through external ventricular drainage. Electrocorticographic (ECoG) activity was continuously recorded between 3 and 13 days after hemorrhage. Autoregulation according to L-PRx was calculated as a moving linear Pearson's correlation of 20-min averages of MAP and ICP. For every identified SD, 60-min intervals of L-PRx were averaged, plotted, and analyzed depending on SD occurrence. Random L-PRx recording periods without SDs served as the control. RESULTS: A total of 19 patients (HD n = 14, BE n = 5, mean age 50.4 years, 9 female patients) were monitored for a mean duration of 230.4 h (range 96-360, STD ± 69.6 h), during which ECoG recordings revealed a total number of 277 SDs. Of these, 184 represented a single SD, and 93 SDs presented in clusters. In HD patients, mean L-PRx values were 0.12 (95% confidence interval [CI] 0.11-0.13) during SDs and 0.07 (95% CI 0.06-0.08) during control periods (p < 0.001). Similarly, in BE patients, a higher L-PRx value of 0.11 (95% CI 0.11-0.12) was detected during SDs than that during control periods (0.08, 95% CI 0.07-0.09; p < 0.001). In a more detailed analysis, CA changes registered through an intraparenchymal probe (HD patients) revealed that clustered SD periods were characterized by signs of more severely impaired CA (L-PRx during SD in clusters: 0.23 [95% CI 0.20-0.25]; single SD: 0.09 [95% CI 0.08-0.10]; control periods: 0.07 [95% CI 0.06-0.08]; p < 0.001). This group also showed significant increases in ICP during SDs in clusters compared with single SD and control periods. CONCLUSIONS: Neuromonitoring for simultaneous assessment of cerebrovascular pressure reactivity using 20-min averages of MAP and ICP measured by L-PRx during SD events is feasible. SD occurrence was associated with significant increases in L-PRx values indicative of CA disturbances. An impaired CA was found during SD in clusters when using an intraparenchymal probe. This preliminary study validates the use of cerebrovascular reactivity indices to evaluate CA disturbances during SDs. Our results warrant further investigation in larger prospective patient cohorts.

Perfusion-Dependent Cerebral Autoregulation Impairment in Hemispheric Stroke.

OBJECTIVE: Loss of cerebral autoregulation (CA) plays a key role in secondary neurologic injury. However, the regional distribution of CA impairment after acute cerebral injury remains unclear because, in clinical practice, CA is only assessed within a limited compartment. Here, we performed large-scale regional mapping of cortical perfusion and CA in patients undergoing decompressive surgery for malignant hemispheric stroke. METHODS: In 24 patients, autoregulation over the affected hemisphere was calculated based on direct, 15 to 20-minute cortical perfusion measurement with intraoperative laser speckle imaging and mean arterial blood pressure (MAP) recording. Cortical perfusion was normalized against noninfarcted tissue and 6 perfusion categories from 0% to >100% were defined. The interaction between cortical perfusion and MAP was estimated using a linear random slope model and Pearson correlation. RESULTS: Cortical perfusion and CA impairment were heterogeneously distributed across the entire hemisphere. The degree of CA impairment was significantly greater in areas with critical hypoperfusion (40-60%: 0.42% per mmHg and 60-80%: 0.46% per mmHg) than in noninfarcted (> 100%: 0.22% per mmHg) or infarcted (0-20%: 0.29% per mmHg) areas (*p < 0.001). Pearson correlation confirmed greater CA impairment at critically reduced perfusion (20-40%: r = 0.67; 40-60%: r = 0.68; and 60-80%: r = 0.68) compared to perfusion > 100% (r = 0.36; *p < 0.05). Tissue integrity had no impact on the degree of CA impairment. INTERPRETATION: In hemispheric stroke, CA is impaired across the entire hemisphere to a variable extent. Autoregulation impairment was greatest in hypoperfused and potentially viable tissue, suggesting that precise localization of such regions is essential for effective tailoring of perfusion pressure-based treatment strategies. ANN NEUROL 2021;89:358-368.

Numerical Simulation of Concussive-Generated Cortical Spreading Depolarization to Optimize DC-EEG Electrode Spacing for Noninvasive Visual Detection.

BACKGROUND: Cortical spreading depolarization (SD) is a propagating depolarization wave of neurons and glial cells in the cerebral gray matter. SD occurs in all forms of severe acute brain injury, as documented by using invasive detection methods. Based on many experimental studies of mechanical brain deformation and concussion, the occurrence of SDs in human concussion has often been hypothesized. However, this hypothesis cannot be confirmed in humans, as SDs can only be detected with invasive detection methods that would require either a craniotomy or a burr hole to be performed on athletes. Typical electroencephalography electrodes, placed on the scalp, can help detect the possible presence of SD but have not been able to accurately and reliably identify SDs. METHODS: To explore the possibility of a noninvasive method to resolve this hurdle, we developed a finite element numerical model that simulates scalp voltage changes that are induced by a brain surface SD. We then compared our simulation results with retrospectively evaluated data in patients with aneurysmal subarachnoid hemorrhage from Drenckhahn et al. (Brain 135:853, 2012). RESULTS: The ratio of peak scalp to simulated peak cortical voltage, Vscalp/Vcortex, was 0.0735, whereas the ratio from the retrospectively evaluated data was 0.0316 (0.0221, 0.0527) (median [1st quartile, 3rd quartile], n = 161, p < 0.001, one sample Wilcoxon signed-rank test). These differing values provide validation because their differences can be attributed to differences in shape between concussive SDs and aneurysmal subarachnoid hemorrhage SDs, as well as the inherent limitations in human study voltage measurements. This simulated scalp surface potential was used to design a virtual scalp detection array. Error analysis and visual reconstruction showed that 1 cm is the optimal electrode spacing to visually identify the propagating scalp voltage from a cortical SD. Electrode spacings of 2 cm and above produce distorted images and high errors in the reconstructed image. CONCLUSIONS: Our analysis suggests that concussive (and other) SDs can be detected from the scalp, which could confirm SD occurrence in human concussion, provide concussion diagnosis on the basis of an underlying physiological mechanism, and lead to noninvasive SD detection in the setting of severe acute brain injury.

The Relationship Between Seizures and Spreading Depolarizations in Patients with Severe Traumatic Brain Injury.

BACKGROUND: Both seizures and spreading depolarizations (SDs) are commonly detected using electrocorticography (ECoG) after severe traumatic brain injury (TBI). A close relationship between seizures and SDs has been described, but the implications of detecting either or both remain unclear. We sought to characterize the relationship between these two phenomena and their clinical significance. METHODS: We performed a post hoc analysis of a prospective observational clinical study of patients with severe TBI requiring neurosurgery at five academic neurotrauma centers. A subdural electrode array was placed intraoperatively and ECoG was recorded during intensive care. SDs, seizures, and high-frequency background characteristics were quantified offline using published standards and terminology. The primary outcome was the Glasgow Outcome Scale-Extended score at 6 months post injury. RESULTS: There were 138 patients with valid ECoG recordings; the mean age was 47 ± 19 years, and 104 (75%) were men. Overall, 2,219 ECoG-detected seizures occurred in 38 of 138 (28%) patients in a bimodal pattern, with peak incidences at 1.7-1.8 days and 3.8-4.0 days post injury. Seizures detected on scalp electroencephalography (EEG) were diagnosed by standard clinical care in only 18 of 138 (13%). Of 15 patients with ECoG-detected seizures and contemporaneous scalp EEG, seven (47%) had no definite scalp EEG correlate. ECoG-detected seizures were significantly associated with the severity and number of SDs, which occurred in 83 of 138 (60%) of patients. Temporal interactions were observed in 17 of 24 (70.8%) patients with both ECoG-detected seizures and SDs. After controlling for known prognostic covariates and the presence of SDs, seizures detected on either ECoG or scalp EEG did not have an independent association with 6-month functional outcome but portended worse outcome among those with clustered or isoelectric SDs. CONCLUSIONS: In patients with severe TBI requiring neurosurgery, seizures were half as common as SDs. Seizures would have gone undetected without ECoG monitoring in 20% of patients. Although seizures alone did not influence 6-month functional outcomes in this cohort, they were independently associated with electrographic worsening and a lack of motor improvement following surgery. Temporal interactions between ECoG-detected seizures and SDs were common and held prognostic implications. Together, seizures and SDs may occur along a dynamic continuum of factors critical to the development of secondary brain injury. ECoG provides information integral to the clinical management of patients with TBI.

The Critical Role of Spreading Depolarizations in Early Brain Injury: Consensus and Contention.

BACKGROUND: When a patient arrives in the emergency department following a stroke, a traumatic brain injury, or sudden cardiac arrest, there is no therapeutic drug available to help protect their jeopardized neurons. One crucial reason is that we have not identified the molecular mechanisms leading to electrical failure, neuronal swelling, and blood vessel constriction in newly injured gray matter. All three result from a process termed spreading depolarization (SD). Because we only partially understand SD, we lack molecular targets and biomarkers to help neurons survive after losing their blood flow and then undergoing recurrent SD. METHODS: In this review, we introduce SD as a single or recurring event, generated in gray matter following lost blood flow, which compromises the Na+/K+ pump. Electrical recovery from each SD event requires so much energy that neurons often die over minutes and hours following initial injury, independent of extracellular glutamate. RESULTS: We discuss how SD has been investigated with various pitfalls in numerous experimental preparations, how overtaxing the Na+/K+ ATPase elicits SD. Elevated K+ or glutamate are unlikely natural activators of SD. We then turn to the properties of SD itself, focusing on its initiation and propagation as well as on computer modeling. CONCLUSIONS: Finally, we summarize points of consensus and contention among the authors as well as where SD research may be heading. In an accompanying review, we critique the role of the glutamate excitotoxicity theory, how it has shaped SD research, and its questionable importance to the study of early brain injury as compared with SD theory.

Questioning Glutamate Excitotoxicity in Acute Brain Damage: The Importance of Spreading Depolarization.

BACKGROUND: Within 2 min of severe ischemia, spreading depolarization (SD) propagates like a wave through compromised gray matter of the higher brain. More SDs arise over hours in adjacent tissue, expanding the neuronal damage. This period represents a therapeutic window to inhibit SD and so reduce impending tissue injury. Yet most neuroscientists assume that the course of early brain injury can be explained by glutamate excitotoxicity, the concept that immediate glutamate release promotes early and downstream brain injury. There are many problems with glutamate release being the unseen culprit, the most practical being that the concept has yielded zero therapeutics over the past 30 years. But the basic science is also flawed, arising from dubious foundational observations beginning in the 1950s METHODS: Literature pertaining to excitotoxicity and to SD over the past 60 years is critiqued. RESULTS: Excitotoxicity theory centers on the immediate and excessive release of glutamate with resulting neuronal hyperexcitation. This instigates poststroke cascades with subsequent secondary neuronal injury. By contrast, SD theory argues that although SD evokes some brief glutamate release, acute neuronal damage and the subsequent cascade of injury to neurons are elicited by the metabolic stress of SD, not by excessive glutamate release. The challenge we present here is to find new clinical targets based on more informed basic science. This is motivated by the continuing failure by neuroscientists and by industry to develop drugs that can reduce brain injury following ischemic stroke, traumatic brain injury, or sudden cardiac arrest. One important step is to recognize that SD plays a central role in promoting early neuronal damage. We argue that uncovering the molecular biology of SD initiation and propagation is essential because ischemic neurons are usually not acutely injured unless SD propagates through them. The role of glutamate excitotoxicity theory and how it has shaped SD research is then addressed, followed by a critique of its fading relevance to the study of brain injury. CONCLUSIONS: Spreading depolarizations better account for the acute neuronal injury arising from brain ischemia than does the early and excessive release of glutamate.

Oxygen-Induced and pH-Induced Direct Current Artifacts on Invasive Platinum/Iridium Electrodes for Electrocorticography.

BACKGROUND: Spreading depolarization (SD) and the initial, still reversible phase of neuronal cytotoxic edema in the cerebral gray matter are two modalities of the same process. SD may thus serve as a real-time mechanistic biomarker for impending parenchyma damage in patients during neurocritical care. Using subdural platinum/iridium (Pt/Ir) electrodes, SD is observed as a large negative direct current (DC) shift. Besides SD, there are other causes of DC shifts that are not to be confused with SD. Here, we systematically analyzed DC artifacts in ventilated patients by observing changes in the fraction of inspired oxygen. For the same change in blood oxygenation, we found that negative and positive DC shifts can simultaneously occur at adjacent Pt/Ir electrodes. METHODS: Nurses and intensivists typically increase blood oxygenation by increasing the fraction of inspired oxygen at the ventilator before performing manipulations on the patient. We retrospectively identified 20 such episodes in six patients via tissue partial pressure of oxygen (ptiO2) measurements with an intracortical O2 sensor and analyzed the associated DC shifts. In vitro, we compared Pt/Ir with silver/silver chloride (Ag/AgCl) to assess DC responses to changes in pO2, pH, or 5-min square voltage pulses and investigated the effect of electrode polarization on pO2-induced DC artifacts. RESULTS: Hyperoxygenation episodes started from a ptiO2 of 37 (30-40) mmHg (median and interquartile range) reaching 71 (50-97) mmHg. During a total of 20 episodes on each of six subdural Pt/Ir electrodes in six patients, we observed 95 predominantly negative responses in six patients, 25 predominantly positive responses in four patients, and no brain activity changes. Adjacent electrodes could show positive and negative responses simultaneously. In vitro, Pt/Ir in contrast with Ag/AgCl responded to changes in either pO2 or pH with large DC shifts. In response to square voltage pulses, Pt/Ir falsely showed smaller DC shifts than Ag/AgCl, with the worst performance under anoxia. In response to pO2 increase, Pt/Ir showed DC positivity when positively polarized and DC negativity when negatively polarized. CONCLUSIONS: The magnitude of pO2-induced subdural DC shifts by approximately 6 mV was similar to that of SDs, but they did not show a sequential onset at adjacent recording sites, could be either predominantly negative or positive in contrast with the always negative DC shifts of SD, and were not accompanied by brain activity depression. Opposing polarities of pO2-induced DC artifacts may result from differences in baseline electrode polarization or subdural ptiO2 inhomogeneities relative to subdermal ptiO2 at the quasi-reference.

Comparison of a New IgG-EIA for the Detection of Anti-Plasmodium Antibodies with Two Currently Used Assays.

BACKGROUND: Malaria is a mosquito-borne infectious disease caused by protozoan parasites of the genus Plasmodium. As migration of populations from endemic areas to Europe and overseas recreational travel to endemic regions increase, there is also a growing risk of transfusion-transmitted tropical diseases by blood components. MATERIAL AND METHODS: In the present study two routine Plasmodium spp. ELISA (CAPTIA™ Malaria EIA, Trinity Biotech, and Malaria EIA, BioRad) were compared with a new commercial ELISA (ELISA IgG, EUROIMMUN). From December 1, 2015 until November 30, 2016, 1,096 plasma samples from blood donors with a potential risk of malaria infection were collected at two blood transfusion centres in Germany and Switzerland. RESULTS: The samples were tested comparatively with the ELISA from EUROIMMUN and the routine test used at the respective centre. Thirty-four of 595 (5.7%) tested blood samples from centre 1 and 49 of 501 (9.8%) tested blood samples from centre 2 showed reactivity on either or both ELISAs. All 83 reactive samples were sent for confirmation to the Diagnostic Centre of the Swiss Tropical and Public Health Institute (Swiss TPH) in Basel, Switzerland. Sixteen samples, which previously were reactive in the routine Plasmodium spp. EIA assays, were proven positive after confirmation testing (i.e., 4 positive and 12 inconclusive results), indicating an anti-Plasmodium antibody prevalence in blood donations of 1.5%. From these 16 reactive samples, 13 were also detected by the index test, resulting in an assay sensitivity of 81.2%. A specificity of 98.6% was calculated (1,065/1,080 confirmed negative samples). The overall agreement with the reference centre was 95.8% in centre 1 and 94% in centre 2. CONCLUSION: The comparison of the new EUROIMMUN ELISA and the established CAPTIA™ Malaria EIA (Trinity Biotech) and Malaria EIA (BioRad) used for routine blood donor screening in two laboratory blood donation centres revealed that all tested ELISAs show comparable sensitivities and are equally suitable for anti-Plasmodium antibody screening in blood banks.

Brainstem and Cortical Spreading Depolarization in a Closed Head Injury Rat Model.

Traumatic brain injury (TBI) is the leading cause of death in young individuals, and is a major health concern that often leads to long-lasting complications. However, the electrophysiological events that occur immediately after traumatic brain injury, and may underlie impact outcomes, have not been fully elucidated. To investigate the electrophysiological events that immediately follow traumatic brain injury, a weight-drop model of traumatic brain injury was used in rats pre-implanted with epidural and intracerebral electrodes. Electrophysiological (near-direct current) recordings and simultaneous alternating current recordings of brain activity were started within seconds following impact. Cortical spreading depolarization (SD) and SD-induced spreading depression occurred in approximately 50% of mild and severe impacts. SD was recorded within three minutes after injury in either one or both brain hemispheres. Electrographic seizures were rare. While both TBI- and electrically induced SDs resulted in elevated oxidative stress, TBI-exposed brains showed a reduced antioxidant defense. In severe TBI, brainstem SD could be recorded in addition to cortical SD, but this did not lead to the death of the animals. Severe impact, however, led to immediate death in 24% of animals, and was electrocorticographically characterized by non-spreading depression (NSD) of activity followed by terminal SD in both cortex and brainstem.

What Should a Clinician Do When Spreading Depolarizations are Observed in a Patient?

The International Conference on Spreading Depolarizations (iCSD) held in Boca Raton, Florida, in the September of 2018 devoted a section to address the question, "What should a clinician do when spreading depolarizations are observed in a patient?" Discussants represented a wide range of expertise, including neurologists, neurointensivists, neuroradiologists, neurosurgeons, and pre-clinical neuroscientists, to provide both clinical and basic pathophysiology perspectives. A draft summary of viewpoints offered was then written by a multidisciplinary writing group of iCSD members, based on a transcript of the session. Feedback of all discussants was formally collated, reviewed, and incorporated into the final document which was subsequently approved by all authors.

Which Spreading Depolarizations Are Deleterious To Brain Tissue?

Spreading depolarizations (SDs) are profound disruptions of cellular homeostasis that slowly propagate through gray matter and present an extraordinary metabolic challenge to brain tissue. Recent work has shown that SDs occur commonly in human patients in the neurointensive care setting and have established a compelling case for their importance in the pathophysiology of acute brain injury. The International Conference on Spreading Depolarizations (iCSD) held in Boca Raton, Florida, in September of 2018 included a discussion session focused on the question of "Which SDs are deleterious to brain tissue?" iCSD is attended by investigators studying various animal species including invertebrates, in vivo and in vitro preparations, diseases of acute brain injury and migraine, computational modeling, and clinical brain injury, among other topics. The discussion included general agreement on many key issues, but also revealed divergent views on some topics that are relevant to the design of clinical interventions targeting SDs. A draft summary of viewpoints offered was then written by a multidisciplinary writing group of iCSD members, based on a transcript of the session. Feedback of all discussants was then formally collated, reviewed and incorporated into the final document. It is hoped that this report will stimulate collection of data that are needed to develop a more nuanced understanding of SD in different pathophysiological states, as the field continues to move toward effective clinical interventions.

Flavin Adenine Dinucleotide Fluorescence as an Early Marker of Mitochondrial Impairment During Brain Hypoxia.

Multimodal continuous bedside monitoring is increasingly recognized as a promising option for early treatment stratification in patients at risk for ischemia during neurocritical care. Modalities used at present are, for example, oxygen availability and subdural electrocorticography. The assessment of mitochondrial function could be an interesting complement to these modalities. For instance, flavin adenine dinucleotide (FAD) fluorescence permits direct insight into the mitochondrial redox state. Therefore, we explored the possibility of using FAD fluorometry to monitor consequences of hypoxia in brain tissue in vitro and in vivo. By combining experimental results with computational modeling, we identified the potential source responsible for the fluorescence signal and gained insight into the hypoxia-associated metabolic changes in neuronal energy metabolism. In vitro, hypoxia was characterized by a reductive shift of FAD, impairment of synaptic transmission and increasing interstitial potassium [K+]o. Computer simulations predicted FAD changes to originate from the citric acid cycle enzyme α-ketoglutarate dehydrogenase and pyruvate dehydrogenase. In vivo, the FAD signal during early hypoxia displayed a reductive shift followed by a short oxidation associated with terminal spreading depolarization. In silico, initial tissue hypoxia followed by a transient re-oxygenation phase due to glucose depletion might explain FAD dynamics in vivo. Our work suggests that FAD fluorescence could be readily used to monitor mitochondrial function during hypoxia and represents a potential diagnostic tool to differentiate underlying metabolic processes for complementation of multimodal brain monitoring.

Cilostazol decreases duration of spreading depolarization and spreading ischemia after aneurysmal subarachnoid hemorrhage.

OBJECTIVE: Traditionally, angiographic vasospasm (aVS) has been thought to cause delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). However, successful treatment of aVS alone does not result in improved neurological outcome. Therefore, there may be other potential causes of poor neurological outcome, including spreading depolarization (SD). A recent study showed beneficial effects of cilostazol on DCI and neurological outcome. The present prospective clinical trial and experimental study focused on effects of cilostazol on SDs. METHODS: Fifty aSAH patients were treated with clip ligation and randomly assigned to a cilostazol (n = 23) or control group (n = 27). Effects of cilostazol on DCI, aVS, and SDs, measured with subdural electrodes, were examined. The effect of cilostazol on SD-induced perfusion deficits (spreading ischemia) was assessed in an aSAH-mimicking model. RESULTS: There was a trend for less DCI in the cilostazol group, but it did not reach our threshold for statistical significance (13.0% vs 40.0%, odds ratio = 0.266, 95% confidence interval [CI] = 0.059-1.192, p = 0.084). However, the total SD-induced depression duration per recording day (22.2 vs 30.2 minutes, ß = -251.905, 95% CI = -488.458 to -15.356, p = 0.043) and the occurrence of isoelectric SDs (0 vs 4 patients, ß = -0.916, 95% CI = -1.746 to -0.085, p = 0.037) were significantly lower in the cilostazol group. In rats, cilostazol significantly shortened SD-induced spreading ischemia compared to vehicle (Student t test, difference = 30.2, 95% CI = 5.3-55.1, p = 0.020). INTERPRETATION: Repair of the neurovascular response to SDs by cilostazol, as demonstrated in the aSAH-mimicking model, may be a promising therapy to control DCI. Ann Neurol 2018;84:873-885.