Stress, the hippocampus, and epilepsy

Psychiatric comorbidities predict seizure recurrence in newly treated adults with epilepsy

OBJECTIVE

At least 30 % to 40 % of patients newly treated for epilepsy experience further seizures despite initiation of appropriate antiseizure medication (ASM) treatment. This study aimed to identify clinically useful predictors of seizure recurrence in newly treated adults with epilepsy which would have major clinical benefits.

METHODS

This work is a prospective cohort study conducted in Northeast China between June 2017 and May 2022. At enrolment, we collected information about demographics, clinical characteristics, and psychiatric comorbidities in newly treated adults with epilepsy. All patients were followed for 12 months for further seizures. Predictors of seizure recurrence were identified using logistic regression analyses.

RESULTS

A total of 836 newly treated adults with epilepsy were included in the final analysis. During follow-up, 362 (43.3 %) patients experienced at least one seizure recurrence, and 474 (56.7 %) entered seizure remission. Multivariable analysis showed that the odds of patients with depression having seizure recurrence were 1.74 times greater than those of patients without depression (Adjusted OR 1.74, 95 % CI 1.21-2.51). Similarly, the odds of patients with anxiety having seizure recurrence were 1.69 times greater than those of patients without anxiety (Adjusted OR 1.69, 95 % CI 1.21-2.37). Other Predictors of seizure recurrence included >5 seizures prior to treatment, brain MRI lesion, EEG epileptiform discharges.

CONCLUSION

We found that psychiatric comorbidities at baseline increase the risk of seizure recurrence in newly treated adults with epilepsy. Future studies are required to clarify the mechanisms underlying the links among psychiatric comorbidities and epilepsy. Furthermore, our findings might inform prospective studies investigating whether psychiatric treatment reduces the risk of seizure recurrence in these patients.

Fatigue, sleep quality, depression symptoms, and antiseizure medication resistance in patients with newly diagnosed epilepsy

Background

Complaints of fatigue and poor sleep quality are common in patients with epilepsy. Fatigue may precipitate seizures, and patients with poor sleep quality have higher frequency of seizures and are more likely to have symptoms of depression.

Objectives

This study aims to determine the association of baseline fatigue and sleep quality with antiseizure medication (ASM) resistance in patients with newly diagnosed epilepsy (PWNDE). We also evaluate whether the association is mediated by depression symptoms.

Methods

We performed a prospective cohort study of PWNDE at comprehensive epilepsy center in Northeast China between June 2020 and May 2024. Fatigue, sleep quality, and depression symptoms were assessed at baseline. All patients were followed for 24 months for ASM-resistant epilepsy. Cox proportional hazard regression models were used to estimate the hazard ratios (HRs) of ASM resistance. Models fitted with restricted cubic spline were performed to test for linear and nonlinear shapes of each association. Mediation analysis was used to estimate the mediating effects of depression severity on association between fatigue, sleep quality, and ASM resistance.

Results

A total of 189 patients (59 ASM-resistant cases and 130 ASM-responsive controls) were included in the final analysis. Baseline fatigue (HR, 1.98; 95% confidence interval (CI), 1.094-3.583, p = 0.024) and poor sleep quality (HR, 2.193; 95% CI, 1.29-3.729, p = 0.004) were associated with an increased hazard of ASM resistance in PWNDE after full adjustments. There exists a nonlinear association between Fatigue Severity Scale score and the hazard of ASM resistance (P for nonlinear = 0.012). Depression severity partly mediated the effect of fatigue and sleep quality on ASM resistance, with mediated proportions of 18.5% for the fatigue and 23.7% for the sleep quality.

Conclusion

Baseline fatigue and poor sleep quality were associated with an increased risk of ASM resistance. The association between fatigue, sleep quality, and ASM resistance were partly mediated by depression severity. These findings emphasize that patients with ASM-resistant epilepsy are more likely to have fatigue, depression, and poor sleep quality at baseline and this may be unrelated to ASM intake.

Perceived stress in adults with epilepsy: A systematic review

This systematic review summarizes evidence about perceived stress in adults with epilepsy to clarify the particularities and potential effects on the prognosis and consequences of the disease. This review follows the recommendations of the PRISMA statement and was registered in PROSPERO. Thirty-four articles were selected. In 89 % of the studies, stress in epilepsy was conceptualized as a process in which the demands of the environment exceed the organism's ability to cope. Stressful life events related to perceived stress in epilepsy included the COVID-19 pandemic and work-related problems. Perceived stress was identified as a seizure precipitant in 85 % of studies. In 67 % of studies, patients with epilepsy had higher perceived stress than healthy people. Female gender, youth, low educational levels, unemployment, poor social support, less than five years suffering the disorder, temporal lobe epilepsy, depression, poor seizure control, and polytherapy were identified as risk factors for increased stress. These studies highlight the need for the conceptualization of epilepsy within a chronic stress framework which could facilitate more appropriate clinical management.

Early life stress influences epilepsy outcomes in mice

Stress is a common seizure trigger that has been implicated in worsening epilepsy outcomes, which encompasses psychiatric and cognitive comorbidities and sudden unexpected death in epilepsy (SUDEP) risk. The neuroendocrine response to stress is mediated by the hypothalamic-pituitary-adrenal (HPA) axis and HPA axis dysfunction worsens epilepsy outcomes, increasing seizure burden, behavioral comorbidities, and risk for SUDEP in mice. Early life stress (ELS) reprograms the HPA axis into adulthood, impacting both the basal and stress-induced activity. Thus, we propose that ELS may influence epilepsy outcomes by influencing the function of the HPA axis. To test this hypothesis, we utilized the maternal separation paradigm and examined the impact on seizure susceptibility. We show that ELS exerts a sex dependent effect on seizure susceptibility in response to acute administration of the chemoconvulsant, kainic acid, which is associated with an altered relationship between seizure activity and HPA axis function. To further examine the impact of ELS on epilepsy outcomes, we utilized the intrahippocampal kainic acid model of chronic epilepsy in mice previously exposed to maternal separation. We find that the relationship between corticosterone levels and the extent of epileptiform activity is altered in mice subjected to ELS. We demonstrate that ELS impacts behavioral outcomes associated with chronic epilepsy in a sex-dependent manner, with females being more affected. We also observe reduced mortality (presumed SUDEP) in female mice subjected to ELS, consistent with previous findings suggesting a role for HPA axis dysfunction in SUDEP risk. These data demonstrate for the first time that ELS influences epilepsy outcomes and suggest that previous life experiences may impact the trajectory of epilepsy.

Dexamethasone attenuates low-frequency brainwave disturbances following acute seizures induced by pentylenetetrazol in Wistar rats

Seizures are neurological disorders triggered by an imbalance in the activity of excitatory and inhibitory neurotransmitters in the brain. When triggered chronically, this imbalance can lead to epilepsy. Critically, many of the affected individuals are refractory to treatment. Given this, anti-inflammatory drugs, in particular glucocorticoids, have been considered as a potential antiepileptogenic therapy. Glucocorticoids are currently used in the treatment of refractory patients, although there have been contradictory results in terms of their use in association with antiepileptic drugs, which reinforces the need for a more thorough investigation of their effects. In this context, the present study evaluated the effects of dexamethasone (DEX, 0.6 mg/kg) on the electroencephalographic (EEG) and histopathological parameters of male Wistar rats submitted to acute seizure induced by pentylenetetrazol (PTZ). The EEG monitoring revealed that DEX reduced the total brainwave power, in comparison with PTZ, in 12 h after the convulsive episode, exerting this effect in up to 36 h (p < 0.05 for all comparisons). An increase in the accommodation of the oscillations of the delta, alpha, and gamma frequencies was also observed from the first 12 h onwards, with the accommodation of the theta frequency occurring after 36 h, and that of the beta frequency 24 h after the seizure. The histopathological analyses showed that the CA3 region and hilum of the hippocampus suffered cell loss after the PTZ-induced seizure (control vs. PTZ, p < 0.05), although DEX was not able to protect these regions against cell death (PTZ vs. DEX + PTZ, p > 0.05). While DEX did not reverse the cell damage caused by PTZ, the data indicate that DEX has beneficial properties in the EEG analysis, which makes it a promising candidate for the attenuation of the epileptiform wave patterns that can precipitate refractory seizures.

Early life stress influences epilepsy outcomes in mice

Stress is a common seizure trigger that has been implicated in worsening epilepsy outcomes. The neuroendocrine response to stress is mediated by the hypothalamic-pituitary-adrenal (HPA) axis and HPA axis dysfunction worsens epilepsy outcomes, increasing seizure burden, behavioral comorbidities, and risk for sudden unexpected death in epilepsy (SUDEP) in mice. Early life stress (ELS) reprograms the HPA axis into adulthood, impacting both the basal and stress-induced activity. Thus, we propose that ELS may influence epilepsy outcomes by influencing the function of the HPA axis. To test this hypothesis, we utilized the maternal separation paradigm and examined the impact on seizure susceptibility. We show that ELS exerts a sex dependent effect on seizure susceptibility in response to acute administration of the chemoconvulsant, kainic acid, which is associated with an altered relationship between seizure activity and HPA axis function. To further examine the impact of ELS on epilepsy outcomes, we utilized the intrahippocampal kainic acid model of chronic epilepsy in mice previously exposed to maternal separation. We find that the relationship between corticosterone levels and the extent of epileptiform activity is altered in mice subjected to ELS. We demonstrate that ELS impacts behavioral outcomes associated with chronic epilepsy in a sex-dependent manner, with females being more affected. We also observe reduced mortality (presumed SUDEP) in female mice subjected to ELS, consistent with previous findings suggesting a role for HPA axis dysfunction in SUDEP risk. These data demonstrate for the first time that ELS influences epilepsy outcomes and suggest that previous life experiences may impact the trajectory of epilepsy.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology (i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, primarily vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process requires neuronal activity and the kinase GSK3β. GCs also dramatically enhance trans-neuronal Tau spreading in vivo, and this effect is blocked by an inhibitor of Tau oligomerization and type 1 unconventional protein secretion. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Stress and Epilepsy: Towards Understanding of Neurobiological Mechanisms for Better Management

Stress has been identified as a major contributor to human disease and is postulated to play a substantial role in epileptogenesis. In a significant proportion of individuals with epilepsy, sensitivity to stressful events contributes to dynamic symptomatic burden, notably seizure occurrence and frequency, and presence and severity of psychiatric comorbidities [anxiety, depression, posttraumatic stress disorder (PTSD)]. Here, we review this complex relationship between stress and epilepsy using clinical data and highlight key neurobiological mechanisms including the hypothalamic-pituitary-adrenal (HPA) axis dysfunction, altered neuroplasticity within limbic system structures, and alterations in neurochemical pathways such as brain-derived neurotrophic factor (BNDF) linking epilepsy and stress. We discuss current clinical management approaches of stress that help optimize seizure control and prevention, as well as psychiatric comorbidities associated with epilepsy. We propose that various shared mechanisms of stress and epilepsy present multiple avenues for the development of new symptomatic and preventative treatments, including disease modifying therapies aimed at reducing epileptogenesis. This would require close collaborations between clinicians and basic scientists to integrate data across multiple scales, from genetics to systems biology, from clinical observations to fundamental mechanistic insights. In future, advances in machine learning approaches and neuromodulation strategies will enable personalized and targeted interventions to manage and ultimately treat stress-related epileptogenesis.

Effects of attachment styles, childhood traumas, and alexithymia in Turkish patients with epilepsy and functional seizures

INTRODUCTION

In this cross-sectional study, we used self-report scales to compare childhood traumas, attachment styles, and alexithymia among patients with functional seizures (FS) to patients with epilepsy and healthy controls. We also investigated risk factors associated with FS.

MATERIAL AND METHODS

A total of 44 patients with epilepsy, 14 patients with FS, and 25 healthy controls were included. All participants were over the age of 18 and were referred to the Baskent University Adana Epilepsy and Video-EEG Center. The patients underwent neurological examinations, brain MRIs, and video-EEG evaluations. Epileptic seizures were classified based on video EEG. The control group consisted of healthy individuals without neurological or psychiatric illness and a history of epileptic seizures or syncope. Beck Depression Inventory (BDI), Childhood Trauma Questionnaire (CTQ), Adult Attachment Scale (AAS), and Toronto Alexithymia Scale-20 (TAS-20) were applied to all participants.

RESULTS

Patients with FS had lower educational levels, higher rates of unemployment and single-marital status. The FS group had higher depression, childhood trauma, and alexithymia scores than the other groups. Furthermore, FS patients had a higher prevalence of avoidant attachment. The alexithymia and childhood trauma scores were both correlated with depression. Through the logistic regression analysis, childhood trauma scores and alexithymia were significant risk factors for FS.

CONCLUSION

The use of video-EEG for diagnosing FS can reduce the risk of misdiagnosis and inappropriate antiepileptic treatment. Psychiatric comorbidities, childhood traumas, and alexithymia are prevalent in patients with FS. Therefore, implementing a multidisciplinary treatment approach that addresses the psychological, medical, and social aspects of FS can significantly improve outcomes.

Effects of season, daytime, sex, and stress on the incidence, latency, frequency, severity, and duration of neonatal seizures in a rat model of birth asphyxia

Neonatal seizures are common in newborn infants after birth asphyxia. They occur more frequently in male than female neonates, but it is not known whether sex also affects seizure severity or duration. Furthermore, although stress and diurnal, ultradian, circadian, or multidien cycles are known to affect epileptic seizures in adults, their potential impact on neonatal seizures is not understood. This prompted us to examine the effects of season, daytime, sex, and stress on neonatal seizures in a rat model of birth asphyxia. Seizures monitored in 176 rat pups exposed to asphyxia on 40 experimental days performed over 3 years were evaluated. All rat pups exhibited seizures when exposed to asphyxia at postnatal day 11 (P11), which in terms of cortical development corresponds to term human babies. A first examination of these data indicated a seasonal variation, with the highest seizure severity in the spring. Sex and daytime did not affect seizure characteristics. However, when rat pups were subdivided into animals that were exposed to acute (short-term) stress after asphyxia (restraint and i.p. injection of vehicle) and animals that were not exposed to this stress, the seizures in stress-exposed rats were more severe but less frequent. Acute stress induced an increase in hippocampal microglia density in sham-exposed rat pups, which may have an additive effect on microglia activation induced by asphyxia. When seasonal data were separately analyzed for stress-exposed vs. non-stress-exposed rat pups, no significant seasonal variation was observed. This study illustrates that without a detailed analysis of all factors, the data would have erroneously indicated significant seasonal variability in the severity of neonatal seizures. Instead, the study demonstrates that even mild, short-lasting postnatal stress has a profound effect on asphyxia-induced seizures, most likely by increasing the activity of the hypothalamic-pituitary-adrenal axis. It will be interesting to examine how postnatal stress affects the treatment and adverse outcomes of birth asphyxia and neonatal seizures in the rat model used here.

Remarkable anecdotes illustrating the nature and effect of seizure-precipitating factors in Border Collies with idiopathic epilepsy

Epilepsy is one of the most common chronic neurological syndromes in dogs and has serious implications for the quality of life of both the dogs and owners. Seizure-precipitating factors (SPFs) (also termed "triggers" or "provocative factors") have been studied and reported in both humans and dogs with idiopathic epilepsy. In dogs stress, hormones, sleep deprivation, and the weather have been reported as SPFs. The Border Collie (BC) is a breed of dog that is predisposed to idiopathic epilepsy, and the outcome is often poor. BC is described as a very sensitive dog with a strong focus on their owners, and this may have an influence on their and their owners' stress level. In this article, we described six unrelated BCs with idiopathic epilepsy in which several remarkable SPFs were identified, and avoiding them improved the outcome of these dogs. The possible SPFs were different for each dog. The SPFs were, among others, the other dog in the family, the lack of intellectual challenge, the presence of an autistic child, a busy street, the relation with the owner, and throwing a ball at the beach. These cases illustrate that recognizing the SPF(s) and taking measures with regard to management can lead to a reduction in epileptic seizure frequency or even achieving seizure freedom.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology (i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process occurs via type 1 unconventional protein secretion (UPS) and requires neuronal activity and the kinase GSK3b. GCs also dramatically enhance trans-neuronal Tau spreading in vivo, and this effect is blocked by an inhibitor of Tau oligomerization and type 1 UPS. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Glucocorticoid stress hormones stimulate vesicle-free Tau secretion and spreading in the brain

Chronic stress and elevated levels of glucocorticoids (GCs), the main stress hormones, accelerate Alzheimer's disease (AD) onset and progression. A major driver of AD progression is the spreading of pathogenic Tau protein between brain regions, precipitated by neuronal Tau secretion. While stress and high GC levels are known to induce intraneuronal Tau pathology ( i.e. hyperphosphorylation, oligomerization) in animal models, their role in trans-neuronal Tau spreading is unexplored. Here, we find that GCs promote secretion of full-length, vesicle-free, phosphorylated Tau from murine hippocampal neurons and ex vivo brain slices. This process occurs via type 1 unconventional protein secretion (UPS) and requires neuronal activity and the kinase GSK3β. GCs also dramatically enhance trans-neuronal Tau spreading in vivo , and this effect is blocked by an inhibitor of Tau oligomerization and type 1 UPS. These findings uncover a potential mechanism by which stress/GCs stimulate Tau propagation in AD.

Noradrenergic stimulation of α1 adrenoceptors in the medial prefrontal cortex mediates acute stress-induced facilitation of seizures in mice

Stress is one of the critical facilitators for seizure induction in patients with epilepsy. However, the neural mechanisms underlying this facilitation remain poorly understood. Here, we investigated whether noradrenaline (NA) transmission enhanced by stress exposure facilitates the induction of medial prefrontal cortex (mPFC)-originated seizures. In mPFC slices, whole-cell current-clamp recordings revealed that bath application of picrotoxin induced sporadic epileptiform activities (EAs), which consisted of depolarization with bursts of action potentials in layer 5 pyramidal cells. Addition of NA dramatically shortened the latency and increased the number of EAs. Simultaneous whole-cell and field potential recordings revealed that the EAs are synchronous in the mPFC local circuit. Terazosin, but not atipamezole or timolol, inhibited EA facilitation, indicating the involvement of α₁ adrenoceptors. Intra-mPFC picrotoxin infusion induced seizures in mice in vivo. Addition of NA substantially shortened the seizure latency, while co-infusion of terazosin into the mPFC inhibited the effect of NA. Finally, acute restraint stress shortened the latency of intra-mPFC picrotoxin infusion-induced seizures, whereas prior infusion of terazosin reversed this stress-induced shortening of seizure latency. Our findings suggest that stress facilitates the induction of mPFC-originated seizures via NA stimulation of α₁ adrenoceptors.

Delay eyeblink conditioning performance and brain-wide c-Fos expression in male and female mice

Delay eyeblink conditioning has been extensively used to study associative learning and the cerebellar circuits underlying this task have been largely identified. However, there is a little knowledge on how factors such as strain, sex and innate behaviour influence performance during this type of learning. In this study, we used male and female mice of C57BL/6J (B6) and B6CBAF1 strains to investigate the effect of sex, strain and locomotion in delay eyeblink conditioning. We performed a short and a long delay eyeblink conditioning paradigm and used a c-Fos immunostaining approach to explore the involvement of different brain areas in this task. We found that both B6 and B6CBAF1 females reach higher learning scores compared to males in the initial stages of learning. This sex-dependent difference was no longer present as the learning progressed. Moreover, we found a strong positive correlation between learning scores and voluntary locomotion irrespective of the training duration. c-Fos immunostainings after the short paradigm showed positive correlations between c-Fos expression and learning scores in the cerebellar cortex and brainstem, as well as previously unreported areas. By contrast, after the long paradigm, c-Fos expression was only significantly elevated in the brainstem. Taken together, we show that differences in voluntary locomotion and activity across brain areas correlate with performance in delay eyeblink conditioning across strains and sexes.

Nicorandil Exerts Anticonvulsant Effects in Pentylenetetrazol-Induced Seizures and Maximal-Electroshock-Induced Seizures by Downregulating Excitability in Hippocampal Pyramidal Neurons

N-(2-hydroxyethyl) nicotinamide nitrate (nicorandil), a nitrate that activates adenosine triphosphate (ATP)-sensitive potassium (K_ATP) channels, is generally used in the treatment of angina and offers long-term cardioprotective effects. It has been reported that several K_ATP channel openers can effectively alleviate the symptoms of seizure. The purpose of this study was to investigate the improvement in seizures induced by nicorandil. In this study, seizure tests were used to evaluate the effect of different doses of nicorandil by analysing seizure incidence, including minimal clonic seizure and generalised tonic-clonic seizure. We used a maximal electroshock seizure (MES) model, a metrazol maximal seizure (MMS) model and a chronic pentylenetetrazol (PTZ)-induced seizure model to evaluate the effect of nicorandil in improving seizures. Each mouse in the MES model was given an electric shock, while those in the nicorandil group received 0.5, 1, 2, 3 and 6 mg/kg of nicorandil by intraperitoneal injection, respectively. In the MMS model, the mice in the PTZ group and the nicorandil group were injected subcutaneously with PTZ (90 mg/kg), and the mice in the nicorandil group were injected intraperitoneally with 1, 3 and 5 mg/kg nicorandil, respectively. In the chronic PTZ-induced seizure model, the mice in the PTZ group and the nicorandil group were injected intraperitoneally with PTZ (40 mg/kg), and the mice in the nicorandil group were each given 1 and 3 mg/kg of PTZ at a volume of 200 nL. Brain slices containing the hippocampus were prepared, and cell-attached recording was used to record the spontaneous firing of pyramidal neurons in the hippocampal CA1 region. Nicorandil (i.p.) significantly increased both the maximum electroconvulsive protection rate in the MES model and the seizure latency in the MMS model. Nicorandil infused directly onto the hippocampal CA1 region via an implanted cannula relieved symptoms in chronic PTZ-induced seizures. The excitability of pyramidal neurons in the hippocampal CA1 region of the mice was significantly increased after both the acute and chronic administration of PTZ. To a certain extent, nicorandil reversed the increase in both firing frequency and proportion of burst spikes caused by PTZ (P < 0.05). Our results suggest that nicorandil functions by downregulating the excitability of pyramidal neurons in the hippocampal CA1 region of mice and is a potential candidate for the treatment of seizures.

Metyrapone abolishes spike-wave discharge seizures in genetic absence epilepsy rats from Strasbourg by reducing stress hormones

OBJECTIVE

Stress is one of the most commonly reported triggers for seizures in patients with epilepsy, although the mechanisms that mediate this effect are not established. The clinical evidence supporting this is derived from patients' subjective experience of stress, and how this influences their own seizures. Animal models can be used to explore this phenomenon in controlled environments, free from subjective bias. Here, we used genetic absence epilepsy rats from Strasbourg (GAERS), a genetic rat model of absence epilepsy, to explore the influence of stress and stress hormones on spontaneous seizures.

METHODS

Adult male GAERS (n = 38) and nonepileptic control (NEC) rats (n = 4) were used. First, rats were subjected to 30-min restraint stress to assess hypothalamic-pituitary-adrenal axis function. Next, we assessed the effects of 30-min noise stress, and cage tilt stress, on spike-wave discharge seizures in GAERS. We then performed pharmacological experiments to assess the direct effects of stress hormones on seizures, including corticosterone, metyrapone, and deoxycorticosterone.

RESULTS

GAERS exhibited elevated baseline corticosterone levels, compared to NEC rats. Noise stress and cage tilt stress significantly enhanced seizure incidence (p < .05), but only during stress periods. Exogenous corticosterone administration also significantly increased seizure occurrence (p < .05). Metyrapone, an inhibitor of corticosterone synthesis, completely abolished seizures in GAERS, and seizures remained suppressed for >2 h. However, deoxycorticosterone, the precursor of corticosterone, increased seizures.

SIGNIFICANCE

These results suggest that GAERS exhibit elevations in stress hormones, and this may contribute to seizures. Inhibiting corticosterone synthesis with metyrapone prevents seizures in GAERS, and shows potential for repurposing this drug as a future antiseizure medication.

The impact of early-life environment on absence epilepsy and neuropsychiatric comorbidities

This review discusses the long-term effects of early-life environment on epileptogenesis, epilepsy, and neuropsychiatric comorbidities with an emphasis on the absence epilepsy. The WAG/Rij rat strain is a well-validated genetic model of absence epilepsy with mild depression-like (dysthymia) comorbidity. Although pathologic phenotype in WAG/Rij rats is genetically determined, convincing evidence presented in this review suggests that the absence epilepsy and depression-like comorbidity in WAG/Rij rats may be governed by early-life events, such as prenatal drug exposure, early-life stress, neonatal maternal separation, neonatal handling, maternal care, environmental enrichment, neonatal sensory impairments, neonatal tactile stimulation, and maternal diet. The data, as presented here, indicate that some early environmental events can promote and accelerate the development of absence seizures and their neuropsychiatric comorbidities, while others may exert anti-epileptogenic and disease-modifying effects. The early environment can lead to phenotypic alterations in offspring due to epigenetic modifications of gene expression, which may have maladaptive consequences or represent a therapeutic value. Targeting DNA methylation with a maternal methyl-enriched diet during the perinatal period appears to be a new preventive epigenetic anti-absence therapy. A number of caveats related to the maternal methyl-enriched diet and prospects for future research are discussed.

Maternal stress induced anxiety-like behavior exacerbated by electromagnetic fields radiation in female rats offspring

There is a disagreement on whether extremely low frequency electromagnetic fields (ELF-EMF) have a beneficial or harmful effect on anxiety-like behavior. Prenatal stress induces frequent disturbances in offspring physiology such as anxiety-like behavior extending to adulthood. This study was designed to evaluate the effects of prenatal stress and ELF-EMF exposure before and during pregnancy on anxiety-like behavior and some anxiety-related pathways in the hippocampus of female rat offspring. A total of 24 female rats 40 days of age were distributed into four groups of 6 rats each: control, Stress (rats whose mothers underwent chronic stress), EMF (rats whose mothers were exposed to electromagnetic fields) and EMF/S (rats whose mothers were simultaneously exposed to chronic stress and ELF-EMF). The rats were given elevated plus-maze and open field tests and then their brains were dissected and their hippocampus were subjected to analysis. ELISA was used to measure 24(S)-hydroxy cholesterol, corticosterone, and serotonin levels. Cryptochrome2, steroidogenic acute regulatory protein, 3B-Hydroxy steroid dehydrogenase, N-methyl-D-aspartate receptor 2(NMDAr2) and phosphorylated N-methyl-D-aspartate receptor 2(PNMDAr2) were assayed by immunoblotting. Anxiety-like behavior increased in all treatment groups at the same time EMF increased anxiety induced by maternal stress in the EMF/S group. The stress group showed decreased serotonin and increased corticosterone levels. ELF-EMF elevated the PNMDAr2/NMDAr2 ratio and 24(S)-hydroxy cholesterol compared to the control group but did not change corticosterone. EMF did not restore changes induced by stress in behavioral and molecular tests. The results of the current study, clarified that ELF-EMF can induce anxiety-like behavior which may be attributed to an increase in the PNMDAr2/NMDAr2 ratio and 24(S)-OHC in the hippocampus, and prenatal stress may contribute to anxiety via a decrease in serotonin and an increase in corticosterone in the hippocampus. We also found that anxiety-like behavior induced by maternal stress exposure, is exacerbated by electromagnetic fields radiation.

Hippocampal interneurons are direct targets for circulating glucocorticoids

The hippocampus has become a significant target of stress research in recent years because of its role in cognitive functioning, neuropathology, and regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Despite the pervasive impact of stress on psychiatric and neurological disease, many of the circuit- and cell-dependent mechanisms giving rise to the limbic regulation of the stress response remain unknown. Hippocampal excitatory neurons generally express high levels of glucocorticoid receptors (GRs) and are therefore positioned to respond directly to serum glucocorticoids. These neurons are, in turn, regulated by neighboring interneurons, subtypes of which have been shown to respond to stress exposure. However, GR expression among hippocampal interneurons is not well characterized. To determine whether key interneuron populations are direct targets for glucocorticoid action, we used two transgenic mouse lines to label parvalbumin-positive (PV+) and somatostatin-positive (SST+) interneurons. GR immunostaining of labeled interneurons was characterized within the dorsal and ventral dentate hilus, dentate cell body layer, and CA1 and CA3 stratum oriens and stratum pyramidale. While nearly all hippocampal SST+ interneurons expressed GR across all regions, GR labeling of PV+ interneurons showed considerable subregion variability. The percentage of PV+, GR+ cells was highest in the CA3 stratum pyramidale and lowest in the CA1 stratum oriens, with other regions showing intermediate levels of expression. Together, these findings indicate that, under baseline conditions, hippocampal SST+ interneurons are a ubiquitous glucocorticoid target, while only distinct populations of PV+ interneurons are direct targets. This anatomical diversity suggests functional differences in the regulation of stress-dependent hippocampal responses.

Hippocampal subfield involvement in patients with transient global amnesia

BACKGROUND AND PURPOSE

Transient global amnesia (TGA) is a rare neurological disorder causing a transient disturbance of episodic long-term memory. Its etiology remains yet to be identified; the only consistently reported findings in patients with TGA are small hyperintense lesions in the hippocampus on diffusion-weighted magnetic resonance imaging (DWI). The aim of this study was to define whether these lesions are subfield specific, as suggested previously.

METHODS

High-resolution multiplanar reformation T1 and DWI of the hippocampus were acquired in 25 patients after TGA with a total of 43 hippocampal lesions. Hippocampal subfields were determined using the FreeSurfer software and the location of the DWI lesions was transformed to the T1 images after data co-registration. Additionally, hippocampal subfield volumes in each patient were calculated and compared with that of 20 healthy controls.

RESULTS

Hippocampal lesions were most frequently detected in the cornu ammonis area 1 (CA1) subfield (30.2%), the hippocampal tail (28.0%), and the subiculum (21.0%); however, lesions were also found in other subfields. There was no significant difference between patients and controls concerning the volumes of the hippocampal subfields.

CONCLUSIONS

Contrasting previous assumptions, we found DWI hyperintense lesions not to be restricted to the CA1 subfield. The visualization of focal hippocampal lesions on diffusion imaging located to several different hippocampal subfields suggests a potential pathophysiology of TGA independent of microstructural hippocampal anatomy and subfield-specific vulnerability.

Using integrated meta-omics to appreciate the role of the gut microbiota in epilepsy

The way the human microbiota may modulate neurological pathologies is a fascinating matter of research. Epilepsy is a common neurological disorder, which has been largely investigated in correlation with microbiota health and function. However, the mechanisms that regulate this apparent connection are scarcely defined, and extensive effort has been conducted to understand the role of microbiota in preventing and reducing epileptic seizures. Intestinal bacteria seem to modulate the seizure frequency mainly by releasing neurotransmitters and inflammatory mediators. In order to elucidate the complex microbial contribution to epilepsy pathophysiology, integrated meta-omics could be pivotal. In fact, the combination of two or more meta-omics approaches allows a multifactorial study of microbial activity within the frame of disease or drug treatments. In this review, we provide information depicting and supporting the use of multi-omics to study the microbiota-epilepsy connection. We described different meta-omics analyses (metagenomics, metatranscriptomics, metaproteomics and metabolomics), focusing on current technical challenges in stool collection procedures, sample extraction methods and data processing. We further discussed the current advantages and limitations of using the integrative approach of multi-omics in epilepsy investigations.

Hippocampal Disinhibition Reduces Contextual and Elemental Fear Conditioning While Sparing the Acquisition of Latent Inhibition

Hippocampal neural disinhibition, i.e., reduced GABAergic inhibition, is a key feature of schizophrenia pathophysiology. The hippocampus is an important part of the neural circuitry that controls fear conditioning and can also modulate prefrontal and striatal mechanisms, including dopamine signaling, which play a role in salience modulation. Consequently, hippocampal neural disinhibition may contribute to impairments in fear conditioning and salience modulation reported in schizophrenia. Therefore, we examined the effect of ventral hippocampus (VH) disinhibition in male rats on fear conditioning and salience modulation, as reflected by latent inhibition (LI), in a conditioned emotional response (CER) procedure. A flashing light was used as the conditioned stimulus (CS), and conditioned suppression was used to index conditioned fear. In experiment 1, VH disinhibition via infusion of the GABA-A receptor antagonist picrotoxin before CS pre-exposure and conditioning markedly reduced fear conditioning to both the CS and context; LI was evident in saline-infused controls but could not be detected in picrotoxin-infused rats because of the low level of fear conditioning to the CS. In experiment 2, VH picrotoxin infusions only before CS pre-exposure did not affect the acquisition of fear conditioning or LI. Together, these findings indicate that VH neural disinhibition disrupts contextual and elemental fear conditioning, without affecting the acquisition of LI. The disruption of fear conditioning resembles aversive conditioning deficits reported in schizophrenia and may reflect a disruption of neural processing both within the hippocampus and in projection sites of the hippocampus.

The Potential Role of Previous Physical Exercise Program to Reduce Seizure Susceptibility: A Systematic Review and Meta-Analysis of Animal Studies

Background: Clinical and pre-clinical studies indicate a reduction in seizure frequency as well as a decrease in susceptibility to subsequently evoked seizures after physical exercise programs. In contrast to the influence of exercise after epilepsy previously established, various studies have been conducted attempting to investigate whether physical activity reduces brain susceptibility to seizures or prevents epilepsy. We report a systematic review and meta-analysis of different animal models that addressed the impact of previous physical exercise programs to reduce seizure susceptibility.

Methods: We included animal model (rats and mice) studies before brain insult that reported physical exercise programs compared with other interventions (sham, control, or naïve). We excluded studies that investigated animal models after brain insult, associated with supplement nutrition or drugs, that did not address epilepsy or seizure susceptibility, ex vivo studies, in vitro studies, studies in humans, or in silico studies. Electronic searches were performed in the MEDLINE (PubMed), Web of Science (WOS), Scopus, PsycINFO, Scientific Electronic Library Online (SciELO) databases, and gray literature, without restrictions to the year or language of publication. We used SYRCLE's risk of bias tool and CAMARADES checklist for study quality. We performed a synthesis of results for different types of exercise and susceptibility to seizures by random-effects meta-analysis.

Results: Fifteen studies were included in the final analysis (543 animals), 13 of them used male animals, and Wistar rats were the most commonly studied species used in the studies (355 animals). The chemoconvulsants used in the selected studies were pentylenetetrazol, penicillin, kainic acid, pilocarpine, and homocysteine. We assessed the impact of study design characteristics and the reporting of mitigations to reduce the risk of bias. We calculated a standardized mean difference effect size for each comparison and performed a random-effects meta-analysis. The meta-analysis included behavioral analysis (latency to seizure onset, n = 6 and intensity of motor signals, n = 3) and electrophysiological analysis (spikes/min, n = 4, and amplitude, n = 6). The overall effect size observed in physical exercise compared to controls for latency to seizure onset was −130.98 [95% CI: −203.47, −58.49] (seconds) and the intensity of motor signals was −0.40 [95% CI: −1.19, 0.40] (on a scale from 0 to 5). The largest effects were observed in electrophysiological analysis for spikes/min with −26.96 [95% CI: −39.56, −14.36], and for spike amplitude (μV) with −282.64 [95% CI: −466.81, −98.47].

Discussion:Limitations of evidence. A higher number of animal models should be employed for analyzing the influence of exerciseon seizure susceptibility. The high heterogeneity in our meta-analysis is attributable to various factors, including the number of animals used in each study and the limited number of similar studies. Interpretation. Studies selected in this systematic review and meta-analysis suggest that previous physical exercise programs can reduce some of the main features related to seizure susceptibility [latency seizure onset, spikes/min, and spike amplitude (μV)] induced by the administration of different chemoconvulsants.

Systematic Review Registration: PROSPERO, identifier CRD42021251949; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=251949.

Impact of COVID-19 Lockdown, during the Two Waves, on Drug Use and Emergency Department Access in People with Epilepsy: An Interrupted Time-Series Analysis

BACKGROUND

In 2020, during the COVID-19 pandemic, Italy implemented two national lockdowns aimed at reducing virus transmission. We assessed whether these lockdowns affected anti-seizure medication (ASM) use and epilepsy-related access to emergency departments (ED) in the general population.

METHODS

We performed a population-based study using the healthcare administrative database of Tuscany. We defined the weekly time series of prevalence and incidence of ASM, along with the incidence of epilepsy-related ED access from 1 January 2018 to 27 December 2020 in the general population. An interrupted time-series analysis was used to assess the effect of lockdowns on the observed outcomes.

RESULTS

Compared to pre-lockdown, we observed a relevant reduction of ASM incidence (0.65; 95% Confidence Intervals: 0.59-0.72) and ED access (0.72; 0.64-0.82), and a slight decrease of ASM prevalence (0.95; 0.94-0.96). During the post-lockdown the ASM incidence reported higher values compared to pre-lockdown, whereas ASM prevalence and ED access remained lower. Results also indicate a lower impact of the second lockdown for both ASM prevalence (0.97; 0.96-0.98) and incidence (0.89; 0.80-0.99).

CONCLUSION

The lockdowns implemented during the COVID-19 outbreaks significantly affected ASM use and epilepsy-related ED access. The potential consequences of these phenomenon are still unknown, although an increased incidence of epilepsy-related symptoms after the first lockdown has been observed. These findings emphasize the need of ensuring continuous care of epileptic patients in stressful conditions such as the COVID-19 pandemic.

Sleep Disruption Worsens Seizures: Neuroinflammation as a Potential Mechanistic Link

Sleep disturbances, such as insomnia, obstructive sleep apnea, and daytime sleepiness, are common in people diagnosed with epilepsy. These disturbances can be attributed to nocturnal seizures, psychosocial factors, and/or the use of anti-epileptic drugs with sleep-modifying side effects. Epilepsy patients with poor sleep quality have intensified seizure frequency and disease progression compared to their well-rested counterparts. A better understanding of the complex relationship between sleep and epilepsy is needed, since approximately 20% of seizures and more than 90% of sudden unexpected deaths in epilepsy occur during sleep. Emerging studies suggest that neuroinflammation, (e.g., the CNS immune response characterized by the change in expression of inflammatory mediators and glial activation) may be a potential link between sleep deprivation and seizures. Here, we review the mechanisms by which sleep deprivation induces neuroinflammation and propose that neuroinflammation synergizes with seizure activity to worsen neurodegeneration in the epileptic brain. Additionally, we highlight the relevance of sleep interventions, often overlooked by physicians, to manage seizures, prevent epilepsy-related mortality, and improve quality of life.

Sex differences in the developing brain impact stress-induced epileptogenicity following hyperthermia-induced seizures

Febrile seizures (FS) are common, affecting 2-5% of children between the ages of 3 months and 6 years. Complex FS occur in 10% of patients with FS and are strongly associated with mesial temporal lobe epilepsy. Current research suggests that predisposing factors, such as genetic and anatomic abnormalities, may be necessary for complex FS to translate to mesial temporal lobe epilepsy. Sex hormones are known to influence seizure susceptibility and epileptogenesis, but whether sex-specific effects of early life stress play a role in epileptogenesis is unclear. Here, we investigate sex differences in the activity of the hypothalamic-pituitary-adrenal (HPA) axis following chronic stress and the underlying contributions of gonadal hormones to the susceptibility of hyperthermia-induced seizures (HS) in rat pups. Chronic stress consisted of daily injections of 40 mg/kg of corticosterone (CORT) subcutaneously from postnatal day (P) 1 to P9 in male and female rat pups followed by HS at P10. Body mass, plasma CORT levels, temperature threshold to HS, seizure characteristics, and electroencephalographic in vivo recordings were compared between CORT- and vehicle (VEH)-injected littermates during and after HS at P10. In juvenile rats (P18-P22), in vitro CA1 pyramidal cell recordings were recorded in males to investigate excitatory and inhibitory neuronal circuits. Results show that daily CORT injections increased basal plasma CORT levels before HS and significantly reduced weight gain and body temperature threshold of HS in both males and females. CORT also significantly lowered the generalized convulsions (GC) latency while increasing recovery time and the number of electrographic seizures (>10s), which had longer duration. Furthermore, sex-specific differences were found in response to chronic CORT injections. Compared to females, male pups had increased basal plasma CORT levels after HS, longer recovery time and a higher number of electrographic seizures (>10s), which also had longer duration. Sex-specific differences were also found at baseline conditions with lower latency to generalized convulsions and longer duration of electrographic seizures in males but not in females. In juvenile male rats, the amplitude of evoked excitatory postsynaptic potentials, as well as the amplitude of inhibitory postsynaptic currents, were significantly greater in CORT rats when compared to VEH littermates. These findings not only validate CORT injections as a stress model, but also show a sex difference in baseline conditions as well as a response to chronic CORT and an impact on seizure susceptibility, supporting a potential link between sustained early-life stress and complex FS. Overall, these effects also indicate a putatively less severe phenotype in female than male pups. Ultimately, studies investigating the biological underpinnings of sex differences as a determining factor in mental and neurologic problems are necessary to develop better diagnostic, preventative, and therapeutic approaches for all patients regardless of their sex.

Case Report: Hypopituitarism Presenting With Nonconvulsive Status Epilepticus

Introduction: Hypopituitarism is defined as one or more partial or complete pituitary hormone deficiencies. Nonconvulsive status epilepticus (NCSE) refers to a state of continuous or repetitive seizures without convulsions. In this paper, we review a case of an old female patient with hypopituitarism who presented with NCSE, which is rare in the clinic.

Case Report: This paper describes a 67-year-old female patient with hypopituitarism who presented as NCSE. She had surgical resection of pituitary tumor half a year before the seizures and did not get regular hormone replacement therapy. She presented general convulsive status epilepsy as the initial symptom and got sedation and antiepileptic drug in the emergency room. The seizure was terminated but the patient fell in coma in the following days. The patient had magnetic resonance imaging (MRI) and other inspects, and EEG showed epileptic discharges. Combining these clinical symptoms and examinations, we made the diagnosis of NCSE. Finally, she regained consciousness after the treatment with diazepam.

Conclusion: This case report and literature review investigated the possible mechanism of hypopituitarism presenting with NCSE.

Past Trauma Is Associated With a Higher Risk of Experiencing an Epileptic Seizure as Traumatic in Patients With Pharmacoresistant Focal Epilepsy

Objective: The present study aimed to evaluate the prevalence of traumatic experienced seizures (TES) and of postepileptic seizure PTSD (PS-PTSD) in patients with pharmacoresistant focal epilepsy and to explore the determining factors of TES.

Methods: We conducted an observational study enrolling 107 adult refractory epilepsy patients. We used the DSM-5 criteria of traumatic events and PTSD to define TES and PS-PTSD. We assessed all traumatic life events unrelated to epilepsy, general and specific psychiatric comorbidities, and quality of life.

Results: Nearly half (n = 48) of the 107 participants reported at least one TES (44.85%). Among these, one-third (n = 16) developed PS-PTSD. The TES group was more likely to experience traumatic events unrelated to epilepsy (p < 0.001), to have generalized anxiety disorder (p = 0.019), and to have specific psychiatric comorbidities [e.g., interictal dysphoric disorder (p = 0.024) or anticipatory anxiety of seizures (p = 0.005)]. They reported a severe impact of epilepsy on their life (p = 0.01). The determining factors of TES according to the multifactorial model were the experience of trauma (p = 0.008), a history of at least one psychiatric disorder (p = 0.03), and a strong tendency toward dissociation (p = 0.03).

Significance: Epileptic seizures may be a traumatic experience in some patients who suffer from pharmacoresistant epilepsy and may be the source of the development of PS-PTSD. Previous trauma unrelated to epilepsy and psychiatric history are determining factors of TES. These clinical entities should be explored systematically.

The glucocorticoid receptor specific modulator CORT108297 reduces brain pathology following status epilepticus

OBJECTIVE

Glucocorticoid levels rise rapidly following status epilepticus and remain elevated for weeks after the injury. To determine whether glucocorticoid receptor activation contributes to the pathological sequelae of status epilepticus, mice were treated with a novel glucocorticoid receptor modulator, C108297.

METHODS

Mice were treated with either C108297 or vehicle for 10 days beginning one day after pilocarpine-induced status epilepticus. Baseline and stress-induced glucocorticoid secretion were assessed to determine whether hypothalamic-pituitary-adrenal axis hyperreactivity could be controlled. Status epilepticus-induced pathology was assessed by quantifying ectopic hippocampal granule cell density, microglial density, astrocyte density and mossy cell loss. Neuronal network function was examined indirectly by determining the density of Fos immunoreactive neurons following restraint stress.

RESULTS

Treatment with C108297 attenuated corticosterone hypersecretion after status epilepticus. Treatment also decreased the density of hilar ectopic granule cells and reduced microglial proliferation. Mossy cell loss, on the other hand, was not prevented in treated mice. C108297 altered the cellular distribution of Fos protein but did not restore the normal pattern of expression.

INTERPRETATION

Results demonstrate that baseline corticosterone levels can be normalized with C108297, and implicate glucocorticoid signaling in the development of structural changes following status epilepticus. These findings support the further development of glucocorticoid receptor modulators as novel therapeutics for the prevention of brain pathology following status epilepticus.

Resting-state functional connectivity of the human hippocampus in periadolescent children: Associations with age and memory performance

The hippocampus is necessary for declarative (relational) memory, and the ability to form hippocampal‐dependent memories develops through late adolescence. This developmental trajectory of hippocampal‐dependent memory could reflect maturation of intrinsic functional brain networks, but resting‐state functional connectivity (rs‐FC) of the human hippocampus is not well‐characterized for periadolescent children. Measuring hippocampal rs‐FC in periadolescence would thus fill a gap, and testing covariance of hippocampal rs‐FC with age and memory could inform theories of cognitive development. Here, we studied hippocampal rs‐FC in a cross‐sectional sample of healthy children (N = 96; 59 F; age 9–15 years) using a seed‐based approach, and linked these data with NIH Toolbox measures, the Picture‐Sequence Memory Test (PSMT) and the List Sorting Working Memory Test (LSWMT). The PSMT was expected to rely more on hippocampal‐dependent memory than the LSWMT. We observed hippocampal rs‐FC with an extensive brain network including temporal, parietal, and frontal regions. This pattern was consistent with prior work measuring hippocampal rs‐FC in younger and older samples. We also observed novel, regionally specific variation in hippocampal rs‐FC with age and hippocampal‐dependent memory but not working memory. Evidence consistent with these findings was observed in a second, validation dataset of similar‐age healthy children drawn from the Philadelphia Neurodevelopment Cohort. Further, a cross‐dataset analysis suggested generalizable properties of hippocampal rs‐FC and covariance with age and memory. Our findings connect prior work by describing hippocampal rs‐FC and covariance with age and memory in typically developing periadolescent children, and our observations suggest a developmental trajectory for brain networks that support hippocampal‐dependent memory.

Significance of serum neuron-specific enolase in transient global amnesia

Neuron-specific enolase (NSE) is a glycolytic enzyme, which is associated with neuronal cell dysfunction in the brain. This study evaluated the role of serum NSE levels of patients with transient global amnesia (TGA). In addition, the relationship between serum NSE levels and the clinical features of TGA was explored. Forty-eight patients with TGA were prospectively included, and their serum NSE levels were measured. We investigated serum NSE levels in patients with TGA. In addition, we analyzed the differences in clinical characteristics between patients with elevated and normal serum NSE levels. Of the 48 patients with TGA, 16 patients (33.3%) had elevated serum NSE levels (25.0 ± 11.5 ng/mL), whereas 32 patients (66.7%) showed normal serum NSE levels (12.8 ± 2.1 ng/mL). The patients with elevated serum NSE levels exhibited higher levels of cognitive impairment than those with normal serum NSE levels (4/16 vs. 1/32, p = 0.036). The serum NSE levels showed a relatively high discrimination (AUC 0.684) between patients with and without cognitive impairment, with 80.0% sensitivity and 74.4% specificity at a cut-off value 17.3 ng/mL. A third of all patients with TGA carry elevated serum NSE levels, which suggests that the neuronal cell dysfunction could be associated with TGA pathogenesis. In addition, it might be correlated with cognitive impairment.

Impact of Stress on Epilepsy: Focus on Neuroinflammation-A Mini Review

Epilepsy, one of the most common neurological disorders worldwide, is characterized by recurrent seizures and subsequent brain damage. Despite strong evidence supporting a deleterious impact on seizure occurrence and outcome severity, stress is an overlooked component in people with epilepsy. With regard to stressor duration and timing, acute stress can be protective in epileptogenesis, while chronic stress often promotes seizure occurrence in epilepsy patients. Preclinical research suggests that chronic stress promotes neuroinflammation and leads to a depressive state. Depression is the most common psychiatric comorbidity in people with epilepsy, resulting in a poor quality of life. Here, we summarize studies investigating acute and chronic stress as a seizure trigger and an important factor that worsens epilepsy outcomes and psychiatric comorbidities. Mechanistic insight into the impact of stress on epilepsy may create a window of opportunity for future interventions targeting neuroinflammation-related disorders.

Stress enhances hippocampal neuronal synchrony and alters ripple-spike interaction

Adverse effects of chronic stress include anxiety, depression, and memory deficits. Some of these stress-induced behavioural deficits are mediated by impaired hippocampal function. Much of our current understanding about how stress affects the hippocampus has been derived from post-mortem analyses of brain slices at fixed time points. Consequently, neural signatures of an ongoing stressful experiences in the intact brain of awake animals and their links to later hippocampal dysfunction remain poorly understood. Further, no information is available on the impact of stress on sharp-wave ripples (SPW-Rs), high frequency oscillation transients crucial for memory consolidation. Here, we used in vivo tetrode recordings to analyze the dynamic impact of 10 days of immobilization stress on neural activity in area CA1 of mice. While there was a net decrease in pyramidal cell activity in stressed animals, a greater fraction of CA1 spikes occurred specifically during sharp-wave ripples, resulting in an increase in neuronal synchrony. After repeated stress some of these alterations were visible during rest even in the absence of stress. These findings offer new insights into stress-induced changes in ripple-spike interactions and mechanisms through which chronic stress may interfere with subsequent information processing.

Psychotic symptoms in drug resistant epilepsy patients after cortical stimulation

PURPOSE

The use of invasive EEG (iEEG) recordings before epilepsy surgery has increased as more complex focal epilepsies are evaluated. Psychotic symptoms (PS) during iEEG have been scarcely reviewed. We aim to report our series of patients with psychotic symptoms (PS) brought about by cortical stimulation (CS) and to identify triggers.

METHODS

Retrospective cohort of patients who underwent iEEG and CS. We report patients who developed delusional thinking and/or disorganized behaviour within 24 h after CS. Exclusion criteria were primary psychiatric disorders or absence of CS.

RESULTS

We evaluated 32 (SEEG 23; subdural 9) patients with a median age of 38 years, 6 with PS. Patients underwent 2586 stimulations over 1130 contacts. Age at CS was significantly higher in patients with PS. Temporal lobe epilepsy was significantly more often documented in patients with PS (χ²: 3.94; p< 0.05). We found no correlation between stimulation of the limbic system and development of psychosis. Four (66.7 %) patients were stimulated in the non-dominant limbic system and developed psychosis compared to 7 (27 %) who did not [χ2: 3.41; p= 0.06].Epilepsy duration was significantly higher in PS patients (p=0.002). Patients with history of postictal psychosis were twice more likely to experience PS(p=0.04).

CONCLUSIONS

PS may arise more frequently in patients with PIP history, older age and longer epilepsy duration. The neurobiology and physiology of psychosis, that may share common mechanisms with epilepsy, is yet to be identified but we hypothesize that it may be triggered by CS due to alteration of brain networks dynamics.

Maternal behavior and the neonatal HPA axis in the Wistar Audiogenic Rat (WAR) strain: Early-life implications for a genetic animal model in epilepsy

Epileptogenesis is a multistage process and seizure susceptibility can be influenced by stress early in life. Wistar Audiogenic Rat (WAR) strain is an interesting model to study the association between stress and epilepsy, since it is naturally susceptible to seizures and present changes in the hypothalamus-pituitary-adrenal (HPA) axis activity. All these features are related to the pathogenic mechanisms usually associated with psychiatric comorbidities present in epilepsy. Therefore, the current study aimed to evaluate the neonate HPA axis function and maternal care under control and stress conditions in the WAR strain. Maternal behavior and neonate HPA axis were evaluated in Wistar and WAR strains under rest and after the presence of stressors. We observed that WAR pups present higher plasmatic corticosterone concentration as compared to Wistar pups. Although WAR dams do not show significant altered maternal behavior at rest, there is a higher latency to recover the litter in the pup retrieval test, while some did not recover all the litter. Wistar Audiogenic Rat dams presented similar behaviors to Wistar dams to a female intruder and maternal care with the pups in the maternal defense test. Taken together, these findings indicate that the WAR strain could show HPA axis disruption early in life and dams present altered maternal behavior under stressful events. Those alterations make the WAR strain an interesting model to evaluate vulnerability to epilepsy and its associated neuropsychiatric comorbidities.

Antiepileptic effects of long-term intracerebroventricular infusion of angiotensin-(1-7) in an animal model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most frequent type of epilepsy and is often refractory to pharmacological treatment. In this scenario, extensive research has identified components of the renin-angiotensin system (RAS) as potential therapeutic targets. Therefore, the aim of the present study was to evaluate the effects of long-term treatment with angiotensin-(1-7) [Ang-(1-7)] in male Wistar rats with TLE induced by pilocarpine (PILO). Rats with TLE were submitted to intracerebroventricular (icv) infusion of Ang-(1-7) (200 ng/kg/h) for 28 days, starting at the first spontaneous motor seizure (SMS). Body weight, food intake, and SMS were evaluated daily. Behavioral tests and hippocampal protein levels were also evaluated at the end of the treatment. Ang-(1-7) treatment reduced the frequency of SMS and attenuated low anxiety levels, increased locomotion/exploration, and reduced body weight gain that was induced by TLE. Moreover, Ang-(1-7) positively regulated the hippocampal levels of antioxidant protein catalase and antiapoptotic protein B-cell lymphoma 2 (Bcl-2), as well as mammalian target of rapamycin (mTOR) phosphorylation, which were reduced by TLE. The hippocampal up-regulation of angiotensin type 1 receptor induced by TLE was also attenuated by Ang-(1-7), while the Mas receptor (MasR) was down-regulated compared with epilepsy. These data show that Ang-(1-7) presents an antiepileptic effect, increasing neuroprotection markers and reducing SMS frequency, body weight, and behavior impairments found in TLE. Therefore, Ang-(1-7) is a promising coadjutant therapeutic option for the treatment of TLE.

Clinical characteristics of patients with ischemic stroke after the 2016 Kumamoto earthquake, a multi-center study

OBJECTIVE

To investigate the clinical characteristics of patients with ischemic stroke following the 2016 Kumamoto earthquake.

METHODS

We retrospectively studied patients with ischemic stroke admitted to 5 stroke centers for 1 year after the earthquake. We compared clinical characteristics in these patients (the post-earthquake group) to those in the patients with ischemic stroke admitted during the same period from the previous 3 years (the pre-earthquake group). Additionally, we analyzed the trend of the incidence rate of stroke before and after the earthquake.

RESULTS

A total of 1979 patients were admitted after the earthquake; 5670 (1,890/year on average) patients were admitted before the earthquake. A first-ever ischemic stroke (71 vs. 75%) and premorbid modified Rankin Scale > 1 (26 vs. 29%) were found significantly more frequently in patients after the earthquake. National Institutes of Health Stroke Scale score ≤ 2 at discharge (60 vs. 65%) was found more frequently in patients after the earthquake, although non-discharge to home (65 vs. 70%) was more frequent in patients after the earthquake. Trend analysis revealed a decrease of small vessel occlusion and large artery atherosclerosis in the month after the earthquake.

CONCLUSIONS

The 2016 Kumamoto earthquake may have affected the characteristics of stroke during the early phase of the earthquake and increased the difficulty in returning home.

Epilepsy Associated Depression: An Update on Current Scenario, Suggested Mechanisms, and Opportunities

Depression is one of the most frequent psychiatric comorbidities associated with epilepsy having a major impact on the patient's quality of life. Several screening tools are available to identify and follow up psychiatric disorders in epilepsy. Out of various psychiatric disorders, people with epilepsy (PWE) are at greater risk of developing depression. This bidirectional relationship further hinders pharmacotherapy of comorbid depression in PWE as some antiepileptic drugs (AEDs) worsen associated depression and coadministration of existing antidepressants (ADs) to alleviate comorbid depression has been reported to worsen seizures. Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin and norepinephrine reuptake inhibitors (SNRIs) are first choice of ADs and are considered safe in PWE, but there are no high-quality evidences. Similar to observations in people with depression, PWE also showed pharmacoresistant to available SSRI/SNRIs, which further complicates the disease prognosis. Randomized double-blind placebo-controlled clinical trials are necessary to report efficacy and safety of available ADs in PWE. We should also move beyond ADs, and therefore, we reviewed common pathological mechanisms such as neuroinflammation, dysregulated hypothalamus pituitary adrenal (HPA) axis, altered neurogenesis, and altered tryptophan metabolism responsible for coexistent relationship of epilepsy and depression. Based on these common pertinent pathways involved in the genesis of epilepsy and depression, we suggested novel targets and therapeutic approaches for safe management of comorbid depression in epilepsy.

Fenofibrate protects the neurovascular unit and ameliorates plasma corticosterone levels in pentylenetetrazole-induced kindling seizure in mice

Epileptic seizures are the most common neurological diseases that change the function of neurovascular unit at molecular levels accompanied by activation of a wide variety of neurodegenerative cascades. Based on the pleiotropic functions of peroxisome proliferator-activated receptor-alpha (PPARα), the current study evaluated the neuroprotective effects of fenofibrate (an effective PPARα agonist) on the brain injuries induced by pentylenetetrazole (PTZ)-induced kindling seizure. Adult male NMRI mice were randomly assigned into four groups (n = 14) as follows; control, untreated kindled mice (PTZ) and two fenofibrate-treated kindled groups. Repeated intraperitoneal injections of PTZ (45 mg/kg) were used to develop kindling seizure every 48 h for 21 days. Treated mice were administered orally fenofibrate at doses of 30 and 50 mg/kg/day during the study. Plasma corticosterone and brain levels of brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA) and mRNA transcription of p53, as well as blood-brain barrier (BBB) permeability, were determined at termination of the study. Fenofibrate considerably improved seizure latency and anxiety-like behaviors in treated kindled mice. Fenofibrate at doses of 30 and 50 mg/kg significantly (P < 0.001) decreased plasma corticosterone (56.88 ± 0.80 and 54.81 ± 0.29 ng/mL, respectively) compared to PTZ group (74.96 ± 1.60 ng/mL). It also significantly (P < 0.05) decreased BDNF levels in both treatment groups (8.13 ± 0.14 and 8.74 ± 0.09 ng/mL, respectively) compared to PTZ group (9.68 ± 0.20 ng/mL). Fenofibrate particularly at higher dose significantly (P < 0.01) decreased MDA content and mRNA expression levels of p53 in treated kindled mice by 67% and 28%, respectively, compared to PTZ group. Similarly, 50 mg/kg fenofibrate significantly (P < 0.05) decreased Evans blue extravasation into brain in treated kindled mice (8.72 ± 0.96 µg/g) compared to PTZ group (15.31 ± 2.18 µg/g). Our results revealed the anticonvulsive and neuroprotective effects of fenofibrate in PTZ-induced kindling seizure in mice. Fenofibrate also improved the neurovascular functions at molecular levels in kindling seizure that might be associated with ameliorating the seizure behaviors.

Reliability of additional reported seizure manifestations to identify dissociative seizures

PURPOSE

Descriptions of seizure manifestations (SM), or semiology, can help localize the symptomatogenic zone and subsequently included brain regions involved in epileptic seizures, as well as identify patients with dissociative seizures (DS). Patients and witnesses are not trained observers, so these descriptions may vary from expert review of seizure video recordings of seizures. To better understand how reported factors can help identify patients with DS or epileptic seizures (ES), we evaluated the associations between more than 30 SMs and diagnosis using standardized interviews.

METHODS

Based on patient- and observer-reported data from 490 patients with diagnoses documented by video-electoencephalography, we compared the rate of each SM in five mutually exclusive groups: epileptic seizures (ES), DS, physiologic seizure-like events (PSLE), mixed DS and ES, and inconclusive testing.

RESULTS

In addition to SMs that we described in a prior manuscript, the following were associated with DS: light triggers, emotional stress trigger, pre-ictal and post-ictal headache, post-ictal muscle soreness, and ictal sensory symptoms. The following were associated with ES: triggered by missing medication, aura of déjà vu, and leftward eye deviation. There were numerous manifestations separately associated with mixed ES and DS.

CONCLUSIONS

Reported SM can help identify patients with DS, but no manifestation is pathognomonic for either ES or DS. Patients with mixed ES and DS reported factors divergent from both ES-alone and DS-alone.

Effective connectivity alteration according to recurrence in transient global amnesia

PURPOSE

This study aimed to evaluate alterations in structural covariance network and effective connectivity of the intrahippocampal circuit in patients with transient global amnesia (TGA). We also investigated whether there were differences of them according to recurrence.

METHODS

We enrolled 88 patients with TGA and 50 healthy controls. We classified patients with TGA into two groups: the single event group (N = 77) and recurrent events group (N = 11). We performed volumetric analysis using the FreeSurfer program and structural covariance network analysis based on the structural volumes using a graph theoretical analysis in patients with TGA and healthy controls. The effective connectivity of the intrahippocampal circuit was also evaluated using structural equation modeling.

RESULTS

There were no significant differences between patients with all TGA events/a single TGA event and healthy controls with regard to global structural covariance network. However, patients with recurrent events had significant alterations in global structural covariance network with a decrease in the small-worldness index (0.907 vs. 0.970, p = 0.032). In patients with all events/a single, there were alterations in effective connectivity from the entorhinal cortex to CA4, only. However, in patients with recurrent events, there were alterations in effective connectivity from the subiculum to the fimbria as well as from the entorhinal cortex to CA4 in bilateral hemispheres.

CONCLUSION

Our study revealed significant alterations in structural covariance network and disruption of the intrahippocampal circuit in patients with TGA compared to healthy controls, which is more prominent when amnestic events recurred. It could be related to the pathogenesis of TGA.

Hypothalamic-pituitary-adrenal axis targets for the treatment of epilepsy

Stress is a common seizure trigger in persons with epilepsy. The body's physiological response to stress is mediated by the hypothalamic-pituitary-adrenal (HPA) axis and involves a hormonal cascade that includes corticotropin releasing hormone (CRH), adrenocorticotropin releasing hormone (ACTH) and the release of cortisol (in humans and primates) or corticosterone (in rodents). The prolonged exposure to stress hormones may not only exacerbate pre-existing medical conditions including epilepsy, but may also increase the predisposition to psychiatric comorbidities. Hyperactivity of the HPA axis negatively impacts the structure and function of the temporal lobe of the brain, a region that is heavily involved in epilepsy and mood disorders like anxiety and depression. Seizures themselves damage temporal lobe structures, further disinhibiting the HPA axis, setting off a vicious cycle of neuronal damage and increasing susceptibility for subsequent seizures and psychiatric comorbidity. Treatments targeting the HPA axis may be beneficial both for epilepsy and for associated stress-related comorbidities such as anxiety or depression. This paper will highlight the evidence demonstrating dysfunction in the HPA axis associated with epilepsy which may contribute to the comorbidity of psychiatric disorders and epilepsy, and propose treatment strategies that may dually improve seizure control as well as alleviate stress related psychiatric comorbidities.

Enlarged hippocampal fissure in psychosis of epilepsy

Psychosis of epilepsy (POE) can be a devastating condition, and its neurobiological basis remains unclear. In a previous study, we identified reduced posterior hippocampal volumes in patients with POE. The hippocampus can be further subdivided into anatomically and functionally distinct subfields that, along with the hippocampal fissure, have been shown to be selectively affected in other psychotic disorders and are not captured by gross measures of hippocampal volume. Therefore, in this study, we compared the volume of selected hippocampal subfields and the hippocampal fissure in 31 patients with POE with 31 patients with epilepsy without psychosis. Cortical reconstruction, volumetric segmentation, and calculation of hippocampal subfields and the hippocampal fissure were performed using FreeSurfer. The group with POE had larger hippocampal fissures bilaterally compared with controls with epilepsy, which was significant on the right. There were no significant differences in the volumes of the hippocampal subfields between the two groups. Our findings suggest abnormal development of the hippocampus in POE. They support and expand the neurodevelopmental model of psychosis, which holds that early life stressors lead to abnormal neurodevelopmental processes, which underpin the onset of psychosis in later life. In line with this model, the findings of the present study suggest that enlarged hippocampal fissures may be a biomarker of abnormal neurodevelopment and risk for psychosis in patients with epilepsy.

Sex Differences in the Epilepsies and Associated Comorbidities: Implications for Use and Development of Pharmacotherapies

The epilepsies are common neurologic disorders characterized by spontaneous recurrent seizures. Boys, girls, men, and women of all ages are affected by epilepsy and, in many cases, by associated comorbidities as well. The primary courses of treatment are pharmacological, dietary, and/or surgical, depending on several factors, including the areas of the brain affected and the severity of the epilepsy. There is a growing appreciation that sex differences in underlying brain function and in the neurobiology of epilepsy are important factors that should be accounted for in the design and development of new therapies. In this review, we discuss the current knowledge on sex differences in epilepsy and associated comorbidities, with emphasis on those aspects most informative for the development of new pharmacotherapies. Particular focus is placed on sex differences in the prevalence and presentation of various focal and generalized epilepsies; psychiatric, cognitive, and physiologic comorbidities; catamenial epilepsy in women; sex differences in brain development; the neural actions of sex and stress hormones and their metabolites; and cellular mechanisms, including brain-derived neurotrophic factor signaling and neuronal-glial interactions. Further attention placed on potential sex differences in epilepsies, comorbidities, and drug effects will enhance therapeutic options and efficacy for all patients with epilepsy. SIGNIFICANCE STATEMENT: Epilepsy is a common neurological disorder that often presents together with various comorbidities. The features of epilepsy and seizure activity as well as comorbid afflictions can vary between men and women. In this review, we discuss sex differences in types of epilepsies, associated comorbidities, pathophysiological mechanisms, and antiepileptic drug efficacy in both clinical patient populations and preclinical animal models.

Seizure burden fluctuates with the female reproductive cycle in a mouse model of chronic temporal lobe epilepsy

Women with catamenial epilepsy often experience increased seizure burden near the time of ovulation (periovulatory) or menstruation (perimenstrual). To date, a rodent model of chronic temporal lobe epilepsy (TLE) that exhibits similar endogenous fluctuations in seizures has not been identified. Here, we investigated whether seizure burden changes with the estrous cycle in the intrahippocampal kainic acid (IHKA) mouse model of TLE. Adult female IHKA mice and saline-injected controls were implanted with EEG electrodes in the ipsilateral hippocampus. At one and two months post-injection, 24/7 video-EEG recordings were collected and estrous cycle stage was assessed daily. Seizures were detected using a custom convolutional neural network machine learning process. Seizure burden was compared within each mouse between diestrus and combined proestrus and estrus days (pro/estrus) at two months post-injection. IHKA mice showed higher seizure burden on pro/estrus compared with diestrus, characterized by increased time in seizures and longer seizure duration. When all IHKA mice were included, no group differences were observed in seizure frequency or EEG power. However, increased baseline seizure burden on diestrus was correlated with larger cycle-associated differences, and when analyses were restricted to mice that showed the severe epilepsy typical of the IHKA model, increased seizure frequency on pro/estrus was also revealed. Controls showed no differences in EEG parameters with cycle stage. These results suggest that the stages of proestrus and estrus are associated with higher seizure burden in IHKA mice. The IHKA model may thus recapitulate at least some aspects of reproductive cycle-associated seizure clustering.