Characteristics of postischemic seizures in hyperglycemic rats

Specificity and sensitivity of the SeLECT score in predicting late seizures in patients undergoing intravenous thrombolytic treatment and the effect of diabetes mellitus and leukoaraiosis

BACKGROUND

 Seizures after stroke can negatively affect the prognosis of ischemic stroke and cause a decrease in quality of life. The efficacy of intravenous (IV) recombinant tissue plasminogen activator (rt-PA) treatment in acute ischemic stroke has been demonstrated in many studies, and IV rt-PA treatment has been increasingly used around the world. The SeLECT score is a useful score for the prediction of late seizures after stroke and includes the severity of stroke (Se), large artery atherosclerosis (L), early seizure (E), cortical involvement (C), and the territory of the middle cerebral artery (T). However, the specificity and sensitivity of the SeLECT score have not been studied in acute ischemic stroke patients that received IV rt-PA treatment.

OBJECTIVE

 In the present study, we aimed to validate and develop the SeLECT score in acute ischemic stroke patients receiving IV rt-PA treatment.

METHODS

 The present study included 157 patients who received IV thrombolytic treatment in our third-stage hospital. The 1-year seizure rates of the patients were detected. SeLECT scores were calculated.

RESULTS

 In our study, we found that the SeLECT score had low sensitivity but high specificity for predicting the likelihood of late seizure after stroke in patients administered IV rt-PA therapy. In addition to the SeLECT score, we found that the specificity and sensitivity were higher when we evaluated diabetes mellitus (DM) and leukoaraiosis.

CONCLUSION

 We found that DM was an independent risk factor for late seizures after stroke in a patient group receiving thrombolytic therapy, and late seizures after stroke were less frequent in patients with leukoaraiosis.

Predictive Factors of Acute Symptomatic Seizures in Patients With Ischemic Stroke Due to Large Vessel Occlusion

Introduction

Acute symptomatic seizures (ASz) after ischemic stroke are associated with increased mortality; therefore, identifying predictors of ASz is important. The purpose of this study was to analyze predictors of ASz in a population of patients with ischemic stroke due to large arterial vessel occlusion (LVO).

Materials and Methods

This retrospective study examined patients with acute ischemic stroke caused by LVO between 2016 and 2020. Identification of predictive factors was performed using univariate and subsequent multiple logistic regression analysis. In addition, subgroup analysis regarding seizure semiology and time of seizure occurrence (≤ 24 h and > 24 h after stroke) was performed.

Results

The frequency of ASz among 979 patients was 3.9 % (n = 38). Univariate logistic regression analysis revealed an increased risk of ASz in patients with higher National Institutes of Health Stroke Scale (NIHSS) score at admission or 24 h after admission, hypernatremia at admission ≥ 145 mmol/L, and pneumonia. Further multiple logistic regression analysis revealed that NIHSS 24 h after admission was the strongest predictor of ASz, particularly relating to ASz occurring later than 24 h after stroke. Patients who experienced a seizure within the first 24 h after stroke were more likely to have a generalized tonic-clonic (GTCS) and focal motor seizure; beyond 24 h, seizures with impaired awareness and non-convulsive status epilepticus were more frequent.

Conclusion

NIHSS score 24 h after admission is a strong predictive factor for the occurrence of ASz in patients with ischemic stroke caused by LVO. The semiology of ASz varied over time, with GTCS occurring more frequently in the first 24 h after stroke.

Embracing Biological and Methodological Variance in a New Approach to Pre-Clinical Stroke Testing

High-profile failures in stroke clinical trials have discouraged clinical translation of neuroprotectants. While there are several plausible explanations for these failures, we believe that the fundamental problem is the way clinical and pre-clinical studies are designed and analyzed for heterogeneous disorders such as stroke due to innate biological and methodological variability that current methods cannot capture. Recent efforts to address pre-clinical rigor and design, while important, are unable to account for variability present even in genetically homogenous rodents. Indeed, efforts to minimize variability may lessen the clinical relevance of pre-clinical models. We propose a new approach that recognizes the important role of baseline stroke severity and other factors in influencing outcome. Analogous to clinical trials, we propose reporting baseline factors that influence outcome and then adapting for the pre-clinical setting a method developed for clinical trial analysis where the influence of baseline factors is mathematically modeled and the variance quantified. A new therapy's effectiveness is then evaluated relative to the pooled outcome variance at its own baseline conditions. In this way, an objective threshold for robustness can be established that must be overcome to suggest its effectiveness when expanded to broader populations outside of the controlled environment of the PI's laboratory. The method is model neutral and subsumes sources of variance as reflected in baseline factors such as initial stroke severity. We propose that this new approach deserves consideration for providing an objective method to select agents worthy of the commitment of time and resources in translation to clinical trials.

Reduced expression of IA channels is associated with postischemic seizures in hyperglycemic rats

Poststroke seizures are considered to be the major cause of epilepsy in the elderly. The mechanisms of poststroke seizures remain unclear. A history of diabetes mellitus has been identified as an independent predictor of acute poststroke seizures in stroke patients. The present study sought to reveal the mechanisms for the development of postischemic seizures under hyperglycemic conditions. Transient forebrain ischemia was produced in adult Wistar rats by using the four-vessel occlusion method. At the normal blood glucose level, seizures occurred in ∼50% of rats after 25 min of ischemia. However, in rats with hyperglycemia, the incidence rate of postischemic seizures was significantly increased to 100%. The occurrence of postischemic seizures was not correlated with the severity of brain damage in hyperglycemic rats. Mannitol, an osmotic diuretic agent, could neither prevent postischemic seizures nor alleviate the exacerbated brain damage in the presence of hyperglycemia. K(+) channels play a critical role in controlling neuronal excitability. The expression of A-type K(+) channel subunit Kv4.2 in the hippocampus and the cortex was significantly reduced in hyperglycemic rats with seizures compared with those without seizures. These results suggest that the reduction of Kv4.2 expression could contribute to the development of postischemic seizures in hyperglycemia.

Poststroke epilepsy: occurrence, predictors and treatment

Although a well-known clinical phenomenon, there still remain some questions regarding the definitions, pathophysiology and epidemiology of early and late poststroke seizures and of poststroke epilepsy. Poststroke seizures and epilepsy constitute important complications in patients surviving a stroke. Several studies of the prevalence and possible predictors of poststroke seizures and epilepsy have been undertaken during the past few decades. Unfortunately, these studies have not consistently used the established definitions. There are only few studies concerning treatment of poststroke epilepsy in the elderly, especially regarding the effect of the newer antiepileptic drugs. The aim of this article is to give an overview of the latest studies of poststroke seizures, with special emphasis on poststroke epilepsy, by presenting data on occurrence, predictors and treatment. The results from the recent studies on both poststroke seizures (early and late) and poststroke epilepsy are quite consistent. Poststroke epilepsy appears to occur in 2-4% of patients. The most convincing predictors of late poststroke seizures and epilepsy and treatment options are discussed in this review.

The role of ethanol on the anticonvulsant effect of valproic acid and cortical microvascular changes after epileptogenesis in mice

There have been conflicting reports regarding the role of ethanol in seizure. Another effect of ethanol is vascular damage in cerebral tissue. This study investigates the influence of ethanol on antiepileptic efficacy of valproic acid (VPA) and cerebral microvascular structure. In this study, four groups of mice (25-30 g) received pentylenetetrazole (PTZ) i.p. (37 mg/kg) every other day. Different groups of animals received an injection of saline, ethanol (1 g/kg), VPA (100 mg/kg), or VPA and ethanol 30 min before PTZ. Animals in groups 5 and 6 received only ethanol and saline, respectively. After recording seizure parameters, the animals were sacrificed under deep anesthesia and the brains of the animals were removed and fixed, thereafter coronal sections were prepared from cerebral cortex. Then, the cerebral microvessels were counted in microscopic sections after hematoxylin-eosin staining. Ethanol injection (1 g/kg) for 7 days decreased stage 4 duration and increased latency to the onset of stage 1 and stage 4 of seizure (p < 0.001). Concomitant injection of VPA (5 min before ethanol) and ethanol had significantly stronger anticonvulsant effects than VPA alone (p < 0.001). Furthermore, the findings showed that not only the cerebral microvessels increased significantly in ethanol group compared with saline group (p < 0.05), but also there were morphological changes in vascular endothelium in ethanol group. The obtained results show that short-term ethanol administration has anticonvulsant effects along with VPA, and enhances the anticonvulsant effects of VPA. Furthermore, it is possible that VPA leads to decreased ethanol-induced vascular damage.

Seizures in acute stroke: incidence, risk factors and prognosis

BACKGROUND AND PURPOSE

Studies on post-stroke seizures have produced conflicting results. Our study aim was to further elucidate the incidence and predictive factors of early post-stroke seizures (ES) and their relationship with outcome.

METHODS

relevant clinical data were prospectively collected in 2,053 patients with acute stroke admitted to the Stroke Unit from 2004 to 2008.

RESULTS

Sixty-six patients (8 hemorrhagic and 58 ischemic strokes) aged 73-88 years (mean age 82 years) presented seizures in the first week after stroke onset. The type of ischemic stroke was atherothrombotic in 10 patients, cardioembolic in 21, lacunar in 4, undetermined in 19, and of other etiology in 4. Twenty-seven patients had generalized convulsive, 6 had complex partial, and 33 had simple partial seizures. Status epilepticus was observed in 13 patients. The severity of strokes in patients with ES was greater than in those without (National Institutes of Health Stroke Scale >14 in 50 vs. 25%), so mortality (30 days) was higher (29 vs. 14%). Independent seizure predictors were: total anterior circulation infarct, hemorrhagic transformation, hyperglycemia, and the interaction term diabetes × hyperglycemia.

CONCLUSIONS

ES may be considered a marker of stroke severity. Cortical location of the lesion, hemorrhagic transformation, and hyperglycemia in patients without diabetes are important predictors of ES.

Seizure activity in the rat hippocampus, perirhinal and prefrontal cortex associated with transient global cerebral ischemia

Epileptiform EEG activity associated with ischemia can contribute to early damage of hippocampal neurons, and seizure activity may also lead to dysfunction in extrahippocampal regions. In this study, seizure activity associated with the four-vessel occlusion model of cerebral ischemia was monitored using chronically implanted electrodes in the CA1/subicular region, the perirhinal cortex, and the prefrontal cortex of the rat. Background EEG amplitude was reduced in all recording sites during occlusion, but spiking and bursting activity was also observed. Seizure activity occurred in most animals during the first several hours of reperfusion, but was not observed on subsequent days. Epileptiform spikes and bursts were often synchronous between two or three recording sites, and spikes in the CA1 region also often occurred just prior to spikes in other sites. These results demonstrate that the four-vessel occlusion model can lead to patterns of seizure activity in the hippocampus, prefrontal and perirhinal cortices.

Seizures and Epilepsy After Ischemic Stroke

Background— Although a long-recognized clinical phenomenon, there remain many questions regarding the epidemiology of seizures and epilepsy after ischemic stroke, their effect on outcome, and their treatment.

Summary of Review— Interpretation of the various studies that have been conducted of postischemic stroke seizures and epilepsy are complicated by their heterogeneous designs, inconsistent uses of terminology, small sample sizes, different periods of follow-up, and ambiguities in seizure identification and classification. Estimates of the rate of early postischemic stroke seizures range from 2% to 33%. The rates of late seizures vary from 3% to 67%. The rate of postischemic stroke epilepsy is ≈2% to 4% and is higher in those who have a late seizure. Data reflecting seizure subtypes are limited. Aside from cortical location and, possibly, stroke severity, no other risk factors for postischemic stroke seizures have been consistently demonstrated. Results regarding the impact of postischemic stroke seizures on outcome are inconsistent.

Conclusions— Much additional work is needed to better understand the epidemiology and social impact of postischemic stroke seizures and epilepsy, their prevention, and optimal management.

Hyperglycemia and hypercapnia differently affect post-ischemic changes in protein kinases and protein phosphorylation in the rat cingulate cortex

Hyperglycemia and hypercapnia aggravate intra-ischemic acidosis and subsequent brain damage. However, hyperglycemia causes more extensive post-ischemic damage than hypercapnia, particularly in the cingulate cortex. We investigated the changes in the subcellular distribution of protein kinase Cgamma (PKCgamma) and the Ca2+/calmodulin-dependent protein kinase II (CaMKII), as well as changes in protein tyrosine phosphorylation during and following 10 min normoglycemic, hyperglycemic (plasma glucose approximately 20 mM) and hypercapnic (paCO2) approximately 300 mm Hg) global cerebral ischemia. During reperfusion period, the translocation to cell membranes of PKCgamma, but not CaMKII, was prolonged by intra-ischemic hyperglycemia, while it was only marginally affected by hypercapnia. The tyrosine-phosphorylation of proteins in the synaptosomal membranes, as well as the extracellular signal-regulated kinase (ERK) in the cytosol, markedly increased during reperfusion following hyperglycemic ischemia, but to a lesser degree following hypercapnic ischemia. Our data suggest that PKCgamma, tyrosine kinase and ERK systems are involved in the process of ischemic damage in the cingulate cortex, where hyperglycemia may affect these kinases through an additional mechanism other than exaggerated acidosis.

Histopathologic consequences of hyperglycemic cerebral ischemia during hypothermic cardiopulmonary bypass in pigs

BACKGROUND

This study examined whether 34 degrees C or 31 degrees C hypothermia during global cerebral ischemia with hyperglycemic cardiopulmonary bypass (CPB) in surviving pigs improves electroencephalographic (EEG) recovery and histopathologic scores when compared with normothermic animals.

METHODS

Anesthetized pigs were placed on CPB and randomly assigned to 37 degrees C (n = 9), 34 degrees C (n = 10), or 31 degrees C (n = 8) management. After increasing serum glucose to 300 mg/dL, animals underwent 15 minutes of global cerebral ischemia by temporarily occluding the innominate and left subclavian arteries. Following reperfusion, rewarming, and termination of CPB, animals were recovered for 24 (37 degrees C animals) or 72 hours (34 degrees C and 31 degrees C animals). Daily EEG signals were recorded, and brain histopathology from cortical, hippocampal, and cerebellar regions was graded by an independent observer.

RESULTS

Before ischemia, serum glucose concentrations were similar in the 37 degrees C (307+/-9 mg/dL), 34 degrees C (311+/-14 mg/dL), and 31 degrees C (310+/-15) groups. By the first postoperative day, EEG scores in 31 degrees C animals (4.2+/-0.6) had returned to baseline and were greater than those in the 34 degrees C (3.4+/-0.5) and 37 degrees C (2.5+/-0.4) groups (p < 0.05, respectively, between groups). Cooling to 34 degrees C showed selective improvement over 37 degrees C in hippocampal, temporal cortical, and cerebellar regions, but the greatest improvement in all regions occurred with 31 degrees C. Cumulative neuropathology scores in 31 degrees C animals (13.5+/-2.2) exceeded 34 degrees C (6.8+/-2.2) and 37 degrees C (1.9+/-2.1) animals (p < 0.05, respectively, between groups).

CONCLUSIONS

Hypothermia during CPB significantly reduced the morphologic consequences of severe, temporary cerebral ischemia under hyperglycemic conditions, with the greatest protection at 31 degrees C.

Hyperglycemia enhances extracellular glutamate accumulation in rats subjected to forebrain ischemia

BACKGROUND AND PURPOSE

An increase in serum glucose at the time of acute ischemia has been shown to adversely affect prognosis. The mechanisms for the hyperglycemia-exacerbated damage are not fully understood. The objective of this study was to determine whether hyperglycemia leads to enhanced accumulation of extracellular concentrations of excitatory amino acids and whether such increases correlate with the histopathological outcome.

METHODS

Rats fasted overnight were infused with either glucose or saline 45 minutes before the induction of 15 minutes of forebrain ischemia. Extracellular glutamate, glutamine, glycine, taurine, alanine, and serine concentrations were measured before, during, and after ischemia in both the hippocampus and the neocortex in both control and hyperglycemic animals. The histopathological outcome was evaluated by light microscopy.

RESULTS

There was a significant increase in extracellular glutamate levels in the hippocampus and cerebral cortex in normoglycemic ischemic animals. The increase in glutamate levels in the cerebral cortex, but not in the hippocampus, was significantly higher in hyperglycemic animals than in controls. Correspondingly, exaggerated neuronal damage was observed in neocortical regions in hyperglycemic animals.

CONCLUSIONS

The present results demonstrate that, at least in the neocortex, preischemic hyperglycemia enhances the accumulation of extracellular glutamate during ischemia, providing a tentative explanation for why neuronal damage is exaggerated.

Changes in excitatory and inhibitory circuits of the rat hippocampus 12-14 months after complete forebrain ischemia

Changes in interneuron distribution and excitatory connectivity have been investigated in animals which had survived 12-14 months after complete forebrain ischemia, induced by four-vessel occlusion. Anterograde tracing with Phaseolus vulgaris leucoagglutinin revealed massive Schaffer collateral input even to those regions of the CA1 subfield where hardly any surviving pyramidal cells were found. Boutons of these Schaffer collaterals formed conventional synaptic contacts on dendritic spines and shafts, many of which likely belong to interneurons. Mossy fibres survived the ischemic challenge, however, large mossy terminals showed altered morphology, namely, the number of filopodiae on these terminals decreased significantly. The entorhinal input to the hippocampus did not show any morphological alterations. The distribution of interneurons was investigated by neurochemical markers known to label functionally distinct GABAergic cell populations. In the hilus, spiny interneurons showed a profound decrease in number. This phenomenon was not as obvious in CA3, but the spiny metabotropic glutamate receptor 1alpha-positive non-pyramidal cells, some of which contain calretinin or substance P receptor, disappeared from stratum lucidum of this area. In the CA1 region, somatostatin immunoreactivity disappeared from stratum oriens/lacunosum-moleculare-associated cells, while in metabotropic glutamate receptor 1alpha-stained sections these cells seemed unaffected in number. Other interneurons did not show an obvious decrease in number. In stratum radiatum of the CA1 subfield, some interneuron types had altered morphology: the substance P receptor-positive dendrites lost their characteristic radial orientation, and the metabotropic glutamate receptor 1alpha-expressing cells became extremely spiny. The loss of inhibitory interneurons at the first two stages of the trisynaptic loop coupled with a well-preserved excitatory connectivity among the subfields suggests that hyperexcitability in the surviving dentate gyrus and CA3 may persist even a year after the ischemic impact. The dorsal CA1 region is lost; nevertheless hyperactivity, if it occurs, may have a route to leave the hippocampus via the longitudinally extensive axon collaterals of CA3 pyramidal cells, which may activate the subiculum and entorhinal cortex with a relay in the surviving ventral hippocampal CA1 region.

Audiogenic seizures after neck tourniquet-induced cerebral ischemia in the rat

Development of audiogenic seizures (AGS) and their correlation with neurodegeneration were studied after 7.5 min of whole-brain ischemia. One day post-ischemia, all animals became hyperreactive and responded to auditory stimulation by generalized seizures. Neuronal necrosis developed already 6 h post-ischemia in inferior colliculi, reticular thalamic nucleus and hippocampal hilar region. Repeated ischemia did not induce any neurological changes, suggesting that the neurological effects are consequences of selective neuronal injury.