Elevated plasma corticosterone level and depressive behavior in experimental temporal lobe epilepsy

Peri-ictal psychiatric manifestations in people with epilepsy: An umbrella review

OBJECTIVE

We aimed to conduct an umbrella review to summarize the existing evidence regarding the prevalence of peri-ictal psychiatric manifestations (PM) in people with epilepsy (PWE) including pre-ictal, ictal, and postictal stages.

METHODS

Databases were searched up to June 2023 for systematic reviews (SR) of observational studies that included patients with epilepsy peri-ictal PM. Data selection, data extraction, and risk of bias assessment (with the AMSTAR-2 instrument) were performed by two independent reviewers. We performed a narrative synthesis using previous guidelines. We used a self-developed decision table according to the GRADE system adapted for narrative outcomes if the certainty of outcomes was not determined by systematic review authors.

RESULTS

Four SRs were included comprising 66 primary studies (n = 10 217). Three SRs evaluated one period (pre-ictal, ictal, and postictal), and one did not determine it. During the pre-ictal period, the more prevalent symptom was confusion, although with a low certainty (due to the heterogeneity and serious risk of bias). One systematic review that only included case reports evaluated the ictal period, finding mood/anxiety disorders, psychosis, and personality changes. The postictal period included the most PM (anxiety: 45.0% and depressive symptoms: 43.0%), with very low certainty, due to risk of bias, potential publication bias, heterogeneity, and failure to report the confidence intervals.

SIGNIFICANCE

With very low certainty, epileptic periods are characterized by a wide spectrum of PM, being postictal symptoms the most prevalent, predominantly anxiety, and depressive symptoms. Further understanding of these PM of epilepsy could improve the attention of the people with epilepsy.

PLAIN LANGUAGE SUMMARY

In this review of reviews, we summarize the frequency in which psychiatric manifestations occur in relation to an epileptic seizure. A total of 10 217 patients were reported in the reviews. The most common manifestations included symptoms of anxiety and depression, as well as changes in the normal behavior of the patient. These manifestations occurred most frequently right after the seizure finished.

Microglia as a Game Changer in Epilepsy Comorbid Depression

As one of the most common neurological diseases, epilepsy is often accompanied by psychiatric disorders. Depression is the most universal comorbidity of epilepsy, especially in temporal lobe epilepsy (TLE). Therefore, it is urgently needed to figure out potential mechanisms and the optimization of therapeutic strategies. Microglia play a pivotal role in the coexistent relationship between epilepsy and depression. Activated microglia released cytokines like IL-6 and IL-1β, orchestrating neuroinflammation especially in the hippocampus, worsening both depression and epilepsy. The decrease of intracellular K+ is a common part in various molecular changes. The P2X7-NLRP3-IL-1β is a major inflammatory pathway that disrupts brain network. Extra ATP and CX3CL1 also lead to neuronal excitotoxicity and blood-brain barrier (BBB) disruption. Regulating neuroinflammation aiming at microglia-related molecules is capable of suspending the vicious mutual aggravating circle of epilepsy and depression. Other overlaps between epilepsy and depression lie in transcriptomic, neuroimaging, diagnosis and treatment. Hippocampal sclerosis (HS) and amygdala enlargement (AE) may be the underlying macroscopic pathological changes according to current studies. Extant evidence shows that cognitive behavioral therapy (CBT) and antidepressants like selective serotonin-reuptake inhibitors (SSRIs) are safe, but the effect is limited. Improvement in depression is likely to reduce the frequency of seizure. More comprehensive experiments are warranted to better understand the relationship between them.

Epilepsy and Encephalopathy

BACKGROUND

Epilepsy encompasses more than the predisposition to unprovoked seizures. In children, epileptic activity during (ictal) and between (interictal) seizures has the potential to disrupt normal brain development. The term "epileptic encephalopathy (EE)" refers to the concept that such abnormal activity may contribute to cognitive and behavioral impairments beyond that expected from the underlying cause of the epileptic activity.

METHODS

In this review, we survey the concept of EE across a diverse selection of syndromes to illustrate its broad applicability in pediatric epilepsy. We review experimental evidence that provides mechanistic insights into how epileptic activity has the potential to impact normal brain processes and the development of neural networks. We then discuss opportunities to improve developmental outcomes in epilepsy now and in the future.

RESULTS

Epileptic activity in the brain poses a threat to normal physiology and brain development.

CONCLUSION

Until we have treatments that reliably target and effectively treat the underlying causes of epilepsy, a major goal of management is to prevent epileptic activity from worsening developmental outcomes.

Is depression in patients with temporal lobe epilepsy related to hippocampal sclerosis? A meta-analysis

OBJECTIVE

To systematically evaluate the association between hippocampal sclerosis (HS) and depression in patients with temporal lobe epilepsy (TLE) through a meta-analysis.

METHODS

Chinese and English databases, such as the China National Knowledge Infrastructure (CNKI), Chinese Scientific Journals (VIP), WanFang, the Chinese Biomedical Literature Service System (SinoMed), PubMed and the Web of Science, were searched.

RESULTS

Two evaluators independently screened the literature, extracted data and evaluated the risk of bias in the included studies in accordance with the inclusion and exclusion criteria. RevMan 5.1 was used to analyze the data. A total of 786 patients with epilepsy were included in the study, including 82 depressive patients with HS and 64 depressive patients without HS. The results showed that the TLE patients with HS were more likely to develop depression than those without HS (odds ratio (OR)= 2.14, 95% confidence interval (CI) [1.45, 3.16], Z = 3.85, p = 0.0001).

CONCLUSION

HS can be considered a high-risk factor for depression in patients with TLE, and the correlation is significant. However, the sample size included in the study was small; additional high-quality studies are needed in the future.

Antidepressant Drugs for Seizures and Epilepsy: Where do we Stand?

People with epilepsy (PWE) are more likely to develop depression and both these complex chronic diseases greatly affect health-related quality of life (QOL). This comorbidity contributes to the deterioration of the QOL further than increasing the severity of epilepsy worsening prognosis. Strong scientific evidence suggests the presence of shared pathogenic mechanisms. The correct identification and management of these factors are crucial in order to improve patients' QOL. This review article discusses recent original research on the most common pathogenic mechanisms of depression in PWE and highlights the effects of antidepressant drugs (ADs) against seizures in PWE and animal models of seizures and epilepsy. Newer ADs, such as selective serotonin reuptake inhibitors (SRRI) or serotonin-noradrenaline reuptake inhibitors (SNRI), particularly sertraline, citalopram, mirtazapine, reboxetine, paroxetine, fluoxetine, escitalopram, fluvoxamine, venlafaxine, duloxetine may lead to improvements in epilepsy severity whereas the use of older tricyclic antidepressant (TCAs) can increase the occurrence of seizures. Most of the data demonstrate the acute effects of ADs in animal models of epilepsy while there is a limited number of studies about the chronic antidepressant effects in epilepsy and epileptogenesis or on clinical efficacy. Much longer treatments are needed in order to validate the effectiveness of these new alternatives in the treatment and the development of epilepsy, while further clinical studies with appropriate protocols are warranted in order to understand the real potential contribution of these drugs in the management of PWE (besides their effects on mood).

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.

Phenotypic differences based on lateralization of intrahippocampal kainic acid injection in female mice

Clinical evidence indicates that patients with temporal lobe epilepsy (TLE) often show differential outcomes of comorbid conditions in relation to the lateralization of the seizure focus. A particularly strong relationship exists between the side of seizure focus and the propensity for distinct reproductive endocrine comorbidities in women with TLE. Therefore, here we evaluated whether targeting of left or right dorsal hippocampus for intrahippocampal kainic acid (IHKA) injection, a model of TLE, produces different outcomes in hippocampal granule cell dispersion, body weight gain, and multiple measures of reproductive endocrine dysfunction in female mice. One, two, and four months after IHKA or saline injection, in vivo measurements of estrous cycles and weight were followed by ex vivo examination of hippocampal dentate granule cell dispersion, circulating ovarian hormone and corticosterone levels, ovarian morphology, and pituitary gene expression. IHKA mice with right-targeted injection (IHKA-R) showed greater granule cell dispersion and pituitary Fshb expression compared to mice with left-targeted injection (IHKA-L). By contrast, pituitary expression of Lhb and Gnrhr were higher in IHKA-L mice compared to IHKA-R, but these values were not different from respective saline-injected controls. IHKA-L mice also showed an increased rate of weight gain compared to IHKA-R mice. Increases in estrous cycle length, however, were similar in both IHKA-L and IHKA-R mice. These findings indicate that although major reproductive endocrine dysfunction phenotypes present similarly after targeting left or right dorsal hippocampus for IHKA injection, distinct underlying mechanisms based on lateralization of epileptogenic insult may contribute to produce similar emergent reproductive endocrine outcomes.

Factors not considered in the study of drug-resistant epilepsy: Psychiatric comorbidities, age, and gender

In basic research and clinical practice, the control of seizures has been the most important goal, but it should not be the only one. There are factors that remain poorly understood in the study of refractory epilepsy such as the age and gender of patients and the presence of psychiatric comorbidities. It is known that in patients with drug-resistant epilepsy (DRE), the comorbidities contribute to the deterioration of the quality of life, increase the severity, and worsen the prognosis of epilepsy. Some studies have demonstrated that patients diagnosed with a co-occurrence of epilepsy and psychiatric disorders are more likely to present refractory seizures and the probability of seizure remission after pharmacotherapy is reduced. The evidence of this association suggests the presence of shared pathogenic mechanisms that may include endocrine disorders, neuroinflammatory processes, disturbances of neurotransmitters, and mechanisms triggered by stress. Additionally, significant demographic, clinical, and electrographic differences have been observed between women and men with epilepsy. Epilepsy affects the female gender in a greater proportion, although there are no studies that report whether refractoriness affects more females. The reasons behind these sex differences are unclear; however, it is likely that sex hormones and sex brain differences related to chromosomal genes play an important role. On the other hand, it has been shown in industrialized countries that prevalence of DRE is higher in the elderly when compared to youngsters. Conversely, this phenomenon is not observed in developing regions, where more cases are found in children and young adults. The correct identification and management of these factors is crucial in order to improve the quality of life of the patients.

Factors not considered in the study of drug-resistant epilepsy: Psychiatric comorbidities, age, and gender

In basic research and clinical practice, the control of seizures has been the most important goal, but it should not be the only one. There are factors that remain poorly understood in the study of refractory epilepsy such as the age and gender of patients and the presence of psychiatric comorbidities. It is known that in patients with drug-resistant epilepsy (DRE), the comorbidities contribute to the deterioration of the quality of life, increase the severity, and worsen the prognosis of epilepsy. Some studies have demonstrated that patients diagnosed with a co-occurrence of epilepsy and psychiatric disorders are more likely to present refractory seizures and the probability of seizure remission after pharmacotherapy is reduced. The evidence of this association suggests the presence of shared pathogenic mechanisms that may include endocrine disorders, neuroinflammatory processes, disturbances of neurotransmitters, and mechanisms triggered by stress. Additionally, significant demographic, clinical, and electrographic differences have been observed between women and men with epilepsy. Epilepsy affects the female gender in a greater proportion, although there are no studies that report whether refractoriness affects more females. The reasons behind these sex differences are unclear; however, it is likely that sex hormones and sex brain differences related to chromosomal genes play an important role. On the other hand, it has been shown in industrialized countries that prevalence of DRE is higher in the elderly when compared to youngsters. Conversely, this phenomenon is not observed in developing regions, where more cases are found in children and young adults. The correct identification and management of these factors is crucial in order to improve the quality of life of the patients.

Arc and Homer1 are involved in comorbid epilepsy and depression: A microarray data analysis

BACKGROUND

Depression is one of the most common comorbid psychiatric condition associated with epilepsy. It has a negative impact on the patient's quality of life. However, the underlying molecular mechanisms leading to depression are currently unclear. The aim of this study was to determine the hub genes associated with epilepsy and depression.

METHODS

Gene expression profiles (GSE47752 and GSE20388) were downloaded from the gene expression omnibus (GEO) database. Differentially expressed genes (DEGs) for epilepsy and depression groups were separately searched. Subsequently, network analyses methods were employed to establish protein-protein interaction (PPI) networks, and to perform Gene Ontology (GO) terms and pathway enrichment analyses for co-expressed DEGs.

RESULTS

A total of 772 genes were upregulated in patients with epilepsy whereas 91 genes were up-regulated in patients with depression. In addition, 1304 genes were down-regulated in epilepsy whereas 141 genes were down-regulated in patients with depression. Among co-expressed DEGs, 5 DEGs were up-regulated and 19 were down-regulated. Further analysis revealed that the co-expressed DEGs were involved in regulation of vasculature development, regulation of angiogenesis, glutamate receptor signaling pathway, cellular response to interleukin-1 and positive regulation of protein kinase B signaling. The Arc and Homer1 genes were identified as the common candidate genes involved in the pathogenesis of epilepsy and depression.

CONCLUSIONS

Arc and Homer1 may contribute to the comorbidity of epilepsy and depression.

The Microbiota-Gut-Brain Axis and Epilepsy

Honoured as the second genome in humans, the gut microbiota is involved in a constellation of physiological and pathological processes, including those related to the central nervous system. The communication between the gut microbiota and the brain is realized by a complex bidirectional connection, known as the "microbiota-gut-brain axis", via neuroendocrine, immunological, and direct neural mechanisms. Recent studies indicate that gut dysfunction/dysbiosis is presumably involved in the pathogenesis of and susceptibility to epilepsy. In addition, the reconstruction of the intestinal microbiome through, for example, faecal microbiota transplantation, probiotic intervention, and a ketogenic diet, has exhibited beneficial effects on drug-resistant epilepsy. The purposes of this review are to provide a brief overview of the microbiota-gut-brain axis and to synthesize what is known about the involvement of the gut microbiota in the pathogenesis and treatment of epilepsy, to bring new insight into the pathophysiology of epilepsy and to present a preliminary discussion of novel therapeutic options for epilepsy based on the gut microbiota.

Parvalbumin Role in Epilepsy and Psychiatric Comorbidities: From Mechanism to Intervention

Parvalbumin is a calcium-binding protein present in inhibitory interneurons that play an essential role in regulating many physiological processes, such as intracellular signaling and synaptic transmission. Changes in parvalbumin expression are deeply related to epilepsy, which is considered one of the most disabling neuropathologies. Epilepsy is a complex multi-factor group of disorders characterized by periods of hypersynchronous activity and hyperexcitability within brain networks. In this scenario, inhibitory neurotransmission dysfunction in modulating excitatory transmission related to the loss of subsets of parvalbumin-expressing inhibitory interneuron may have a prominent role in disrupted excitability. Some studies also reported that parvalbumin-positive interneurons altered function might contribute to psychiatric comorbidities associated with epilepsy, such as depression, anxiety, and psychosis. Understanding the epileptogenic process and comorbidities associated with epilepsy have significantly advanced through preclinical and clinical investigation. In this review, evidence from parvalbumin altered function in epilepsy and associated psychiatric comorbidities were explored with a translational perspective. Some advances in potential therapeutic interventions are highlighted, from current antiepileptic and neuroprotective drugs to cutting edge modulation of parvalbumin subpopulations using optogenetics, designer receptors exclusively activated by designer drugs (DREADD) techniques, transcranial magnetic stimulation, genome engineering, and cell grafting. Creating new perspectives on mechanisms and therapeutic strategies is valuable for understanding the pathophysiology of epilepsy and its psychiatric comorbidities and improving efficiency in clinical intervention.

Epilepsy-associated comorbidities among adults: A plausible therapeutic role of gut microbiota

Epilepsy is a debilitating disorder that affects about 70 million people in the world currently. Most patients with epilepsy (PWE) often reported at least one type of comorbid disorder. These may include neuropsychiatric disorders, cognitive deficits, migraine, cardiovascular dysfunction, systemic autoimmune disorders and others. Current treatment strategies against epilepsy-associated comorbidities have been based on targeting each disorder separately with either anti-seizure medications (ASMs), anti-inflammatories or anti-depressant drugs, which have often given inconsistent and ineffective results. Gut dysbiosis may be a common pathological pathway between epilepsy and its comorbid disorders, and thus may serve as a possible intervention target. Therefore, this narrative review aimed to elucidate the potential pathological and therapeutic role of the gut microbiota in adult epilepsy-associated comorbidities. This review noticed a scarcity in the current literature on studies investigating the direct role of the gut microbiota in relation to epilepsy-associated comorbidities. Nevertheless, gut dysbiosis have been implicated in both epilepsy and its associated comorbidities, with similarities seen in the imbalance of certain gut microbiota phyla (Firmicutes), but differences seen in the mechanism of action. Current gut-related interventions such as probiotics have been consistently reported across studies to provide beneficial effects in correcting gut dysbiosis and improving various disorders, independent of epilepsy. However, whether these beneficial effects may translate towards epilepsy-associated comorbidities have yet to be determined. Thus, future studies determining the therapeutic potential of gut microbiota interventions in PWE with epilepsy-associated comorbidities may effectively improve their quality of life.

Comorbidity of Epilepsy and Depression: Associated Pathophysiology and Management

Epilepsy is a neurological disorder characterized by recurrent unprovoked seizures. Depression may arise as a result of other mental or physical problems or as a side effect of the drugs used to treat such illnesses, or it could be caused by epilepsy-related structural abnormalities. However, physicians are hesitant to prescribe antidepressants to patients with epilepsy due to concerns about decreasing seizure thresholds and the harmful drug interactions between antidepressants and antiepileptic medicines. As a result, the question about the optimal care of epileptic patients who suffer from depression remains unanswered. Despite the complicated link between epilepsy and depression, the co-administration of antidepressants and antiepileptic drugs (AEDs) is safe and beneficial when appropriately managed. A focused evaluation for depression (regardless of social, economic, or personal circumstances) might identify people who benefit from medical care and therapeutic assistance. Vagus nerve stimulation and psychological therapies such as cognitive-behavioral therapy, individual or group psychotherapy, patient support groups, family therapy, and counseling are nonpharmacological therapeutic alternatives. In terms of treatment strategy, it is critical to optimize seizure control and limit antiepileptic medications' adverse effects. Psychotherapy for depression in epilepsy is underused, even though it has been shown to be helpful in well-controlled studies. This review article has discussed some parts of the most common pathophysiologies of depression in patients with epilepsy, highlighted the efficacy of psychotherapy and antidepressant drugs, and explored the optimal care of patients with epilepsy who suffer from depression.

The overlapping relationship among depression, anxiety, and somatic symptom disorder and its impact on the quality of life of people with epilepsy

Background:

Emotional disorder is an important indicator for assessing the quality of life (QOL) of people with epilepsy (PWE). Depression, somatic symptom disorder (SSD) and anxiety are among the most frequently occurring mental disorders and overlap with each other.

Objectives:

This study examines the overlap of these three emotional disorders and their effects separately and in combination on the QOL of PWE.

Design:

Cross-sectional study.

Data Sources and Methods:

Adults attending our epilepsy clinic between 1 July 2020 and 1 May 2022 were consecutively enrolled. They were screened for depression, SSD, and anxiety by structured interviews, and demographic, epilepsy-related and QOL indicators were collected. Multivariate analysis, propensity score matching (PSM) and stratified analysis were used to explore the effects of their respective and combined effects on QOL.

Results:

Among the 749 patients, 189 patients (25%) were diagnosed with depression, 183 patients (24%) were diagnosed with SSD, and 157 patients (21%) were diagnosed with anxiety. The frequency of occurrence of each emotional disorder together with other emotional disorders was higher than the frequency of occurrence of an emotional disorder alone. Depression, SSD, and anxiety all had an independent effect on QOL of PWE ( p < 0.001). Depression had the greatest effect, followed by SSD, and then anxiety ( β: multivariate analysis, −11.0 versus –7.8 versus –6.5; PSM, −14.7 versus –9.4 versus –6.8). The QOL of PWE decreased more significantly with the increasing number of comorbid emotional disorders ( β: –12.1 versus –20.7 versus –23.0).

Conclusion:

It is necessary to screen for three emotional disorders, that is, depression, SSD, and anxiety, in PWE. Attention should be paid to people with multiple comorbid emotional disorders.

Bidirectional Relations Among Depression, Migraine, and Epilepsy: Do They Have an Impact on Their Response to Treatment?

The evaluation and treatment of patients with epilepsy is not limited to the type of epilepsy, but it must incorporate the common comorbid neurologic, psychiatric, and medical disorders, as the latter can bare an impact on the course and response to treatment of the seizure disorder and vice versa. In this article we review the bidirectional relations among epilepsy and two of its most common comorbidities, mood disorders and migraine and examine the implications of these relations on the selection of therapies of these three disorders and their response to treatment. We also review the most salient common pathogenic mechanisms that may explain such relations.

The pilocarpine model of mesial temporal lobe epilepsy: Over one decade later, with more rodent species and new investigative approaches

Fundamental work on the mechanisms leading to focal epileptic discharges in mesial temporal lobe epilepsy (MTLE) often rests on the use of rodent models in which an initial status epilepticus (SE) is induced by kainic acid or pilocarpine. In 2008 we reviewed how, following systemic injection of pilocarpine, the main subsequent events are the initial SE, the latent period, and the chronic epileptic state. Up to a decade ago, rats were most often employed and they were frequently analysed only behaviorally. However, the use of transgenic mice has revealed novel information regarding this animal model. Here, we review recent findings showing the existence of specific neuronal events during both latent and chronic states, and how optogenetic activation of specific cell populations modulate spontaneous seizures. We also address neuronal damage induced by pilocarpine treatment, the role of neuroinflammation, and the influence of circadian and estrous cycles. Updating these findings leads us to propose that the rodent pilocarpine model continues to represent a valuable tool for identifying the basic pathophysiology of MTLE.

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.

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.

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.

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.

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.

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.

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.

The effects of microglia‐ and astrocyte‐derived factors on neurogenesis in health and disease

Hippocampal neurogenesis continues throughout life and has been suggested to play an essential role in maintaining spatial cognitive function under physiological conditions. An increasing amount of evidence has indicated that adult neurogenesis is tightly controlled by environmental conditions in the neurogenic niche, which consists of multiple types of cells including microglia and astrocytes. Microglia maintain the environment of neurogenic niche through their phagocytic capacity and interaction with neurons via fractalkine‐CX3CR1 signaling. In addition, microglia release growth factors such as brain‐derived neurotrophic factor (BDNF) and cytokines such as tumor necrosis factor (TNF)‐α to support the development of adult born neurons. Astrocytes also manipulate neurogenesis by releasing various soluble factors including adenosine triphosphate and lactate. Whereas, under pathological conditions such as Alzheimer's disease, depression, and epilepsy, microglia and astrocytes play a leading role in inflammation and are involved in attenuating the normal process of neurogenesis. The modulation of glial functions on neurogenesis in these brain diseases are attracting attention as a new therapeutic target. This review describes how these glial cells play a role in adult hippocampal neurogenesis in both health and disease, especially focusing glia‐derived factors.

Depression and Anxiety in the Epilepsies: from Bench to Bedside

PURPOSE OF REVIEW

Depression and anxiety substantially contribute to interictal disability in patients with epilepsy (PWE). This review summarizes current studies that shed light on mechanisms of comorbidity.

RECENT FINDINGS

Mounting epidemiological data implicate shared risk factors for anxiety/depression and seizure propensity, but these remain largely elusive and probably vary by epilepsy type. Within PWE, these symptoms appear to be associated with unique genetic, neuropathological, and connectivity profiles. Temporal lobe epilepsy has received enormous emphasis particularly in preclinical studies of comorbidity, where candidate neurobiological mechanisms underlying bidirectionality have been tested without psychopharmacological confounds. Depression and anxiety in epilepsy reflect dysfunction within broadly distributed limbic networks that may be the cause or consequence of epileptogenesis. In refractory epilepsy, seizures and/or certain anticonvulsants may distort central emotional homeostatic mechanisms that perpetually raise seizure risk. Developing future safe and effective combined anticonvulsant-antidepressant treatments will require a detailed understanding of anatomical and molecular nodes that pleiotropically enhance seizure risk and negatively alter emotionality.

Network Dysfunction in Comorbid Psychiatric Illnesses and Epilepsy

The episodic nature of both epilepsy and psychiatric illnesses suggests that the brain switches between healthy and pathological states. The most obvious example of transitions between network states related to epilepsy is the manifestation of ictal events. In addition to seizures, there are more subtle changes in network communication within and between brain regions, which we propose may contribute to psychiatric illnesses associated with the epilepsies. This review will highlight evidence supporting aberrant network activity associated with epilepsy and the contribution to cognitive impairments and comorbid psychiatric illnesses. Further, we discuss potential mechanisms mediating the network dysfunction associated with comorbidities in epilepsy, including interneuron loss and hypothalamic–pituitary–adrenal axis dysfunction. Conceptually, it is necessary to think beyond ictal activity to appreciate the breadth of network dysfunction contributing to the spectrum of symptoms associated with epilepsy, including psychiatric comorbidities.

Neuroinflammation impact in epileptogenesis and new treatment strategy

Epilepsy is considered a major serious chronic neurological disorder, characterized by recurrent seizures. It is usually associated with a history of a lesion in the nervous system. Irregular activation of inflammatory molecules in the injured tissue is an important factor in the development of epilepsy. It is unclear how the imbalanced regulation of inflammatory mediators contributes to epilepsy. A recent research goal is to identify interconnected inflammation pathways which may be involved in the development of epilepsy. The clinical use of available antiepileptic drugs is often restricted by their limitations, incidence of several side effects, and drug interactions. So development of new drugs, which modulate epilepsy through novel mechanisms, is necessary. Alternative therapies and diet have recently reported positive treatment outcomes in epilepsy. Vitamin D (Vit D) has shown prophylactic and therapeutic potential in different neurological disorders. So, the aim of current study was to review the associations between different brain inflammatory mediators and epileptogenesis, to strengthen the idea that targeting inflammatory pathway may be an effective therapeutic strategy to prevent or treat epilepsy. In addition, neuroprotective effects and mechanisms of Vit D in clinical and preclinical studies of epilepsy were reviewed.

Audiogenic kindling activates expression of vasopressin in the hypothalamus of Krushinsky-Molodkina rats genetically prone to reflex epilepsy

The present study analysed the effects of audiogenic kindling on the functional state of the vasopressinergic system of Krushinsky-Molodkina (KM) rats. KM rats represent a genetic model of audiogenic reflex epilepsy. Multiple audiogenic seizures in KM rats lead to the involvement of the limbic structures and neocortex in the epileptic network. The phenomenon of epileptic activity that overspreads from the brain stem to the forebrain is called audiogenic kindling and represents a model of limbic epilepsy. In the present study, audiogenic kindling was induced by 25 repetitive audiogenic seizures (AGS) with 1 AGS per day. A proportion of KM rats did not express AGS to sound stimuli, and these rats were characterised as the AGS-resistant group. The data demonstrated that audiogenic kindling did not change activity of extracellular signal-regulated kinase 1/2 or cAMP response element-binding protein, although it led to an increase in vasopressin (VP) expression in the supraoptic nucleus (SON) and in the magnocellular division of the paraventricular nucleus (PVN). Additionally, we observed a decrease in GABAergic innervation of the hypothalamic neuroendocrine neurones after audiogenic kindling, whereas glutamatergic innervation of the SON and PVN was not altered. By contrast, analysis of AGS-resistant KM rats did not reveal any changes in the activity of the VP-ergic system, confirming that the activation of VP expression was caused by repetitive AGS expression, rather than by repetitive acoustic stress. Thus, we suggest that overspread of epileptiform activity in the brain is the main factor that affects VP expression in the hypothalamic magnocellular neurones.

The intersections of stress, anxiety and epilepsy

Stress is ubiquitous in chronic medical conditions; however, the connections to psychiatric and neurologic conditions are not always clearly established. Epilepsy is a unique illness that is intimately intertwined with stress and anxiety not only as a result of the disease process but also as a cause of disease exacerbation. Anxiety and depression also involve stress management and often overlap with epilepsy. Anxiety symptoms themselves may be present as intrinsic aspects of seizure phenomena, either during the events or closely related to them. The pathways of stress and anxiety involve the hypothalamic pituitary adrenal (HPA) axis and explain at least in part how stress may lead to worsening seizure control. Ultimately, the study of stress, anxiety, and epilepsy offers insight into mind and body connections, and furthers understanding of neuropsychiatric illness.

The Therapeutic Effects of Low-Frequency Electrical Stimulations Adjunct to Sodium Valproate on Seizure and Behaviors

Introduction:

Consuming antidepressant medications induce several problems leading to the need for alternative agents for emotional disturbances. Antidepressant medications increase the seizure risk; thus, alternative treatments, like Antiepileptic Drugs (AED), might be useful for patients with epilepsy comorbid with a psychiatric disorder. The present study evaluated the behavioral effects of sodium valproate, a none effective dose in seizure treatment [100 mg/kg; Intraperitoneal (IP)] along with the application of Low-Frequency Stimulations (LFS) during CA1 hippocampal kindling.

Methods:

In total, 42 male rats were randomly divided into 6 groups, including control group with intact animals handled daily (I); sham group which was subjected to the surgical process, but received no real stimulation (II); saline-kindled Kindled group (S.kindled) which were stimulated daily with the following protocol: 3 strain of 50Hz monophasic pulses of 1ms duration applied 12 times a day with the threshold intensity at intervals of 10 minutes where saline was administrated 15 min before kindling stimulations (III); saline-kindled-LFS group (K4LFS) in which saline was injected 15 min before kindling stimulations and LFS was applied daily after the termination of kindling stimulation (IV); drug-kindle group (Drug100.kindled) that underwent rapid kindling procedure daily where sodium valproate (100 mg/kg) was administrated 15 min before kindling stimulations(V), and drug-kindled-LFS (Drug100.kindled.4LFS) group in which drug and LFS were administrated respectively before and after kindling stimulations (VI). The behavioral tests were assessed using elevated plus maze, open field, and forced swim tests.

Results:

The combination of sodium valproate (100 mg/kg) and LFS significantly decreased cumulative seizure severity compared with the kindle group. Thus, it provided a strong seizure suppressing effect. Additionally, sodium valproate and LFS increased the percentage of Open Arms (OAs) entries and the OAs exploration; they also decreased jumping from elevated plus maze test and rearing in open field test. Furthermore, there was no significant change in the OAs entries and OAs exploration percentages, jumping from apparatus, and rearing in open field in Drug100. Kindled, K4LFS, and Drug100.kindled.LFS groups, compared with the sham group. There was no significant difference in the latency to first immobility and the duration of immobility in K4LFS groups compared with the S. kindled group. In the drug-kindled group, the latency to first immobility significantly increased, and the duration of immobility decreased, compared with the S. kindled group. Besides, the latency to first immobility significantly increased, and the duration of immobility decreased in drug-kindled-LFS, compared to S. kindled group; however, the latency to first immobility was not significantly changed, compared to drug-kindled groups.

Conclusion:

Sodium valproate and LFS can modulate the function of the brain regions involved in emotional processing in epilepsy, as well as anxiety- and depressive-like behaviors. Such a combination could also decrease emotional disturbances induced by the kindling process.

Depression in People with Epilepsy. What is the Connection?

INTRODUCTION

Depression is the most common psychiatric comorbidity in people with epilepsy. It worsens the prognosis and quality of life of these patients. Despite this, depression is poorly diagnosed and when the treatment is given, it is frequently suboptimal.

OBJECTIVE

To perform a narrative review of the medical literature, seeking to collect useful information regarding the relationship between epilepsy and depression.

RESULTS

Narrative reviews, systematic reviews, meta-analyses, clinical trials, and follow-up studies were identified in English and Spanish with no time limit, including epidemiological, clinical, associated factors, etiological explanations, diagnostic and therapeutic approaches to comorbid depression in epilepsy.

CONCLUSION

The relationship between epilepsy and depression is complex. The available scientific evidence suggests the possibility of a bidirectional relationship that could be explained from common aetiopathogenic mechanisms. Despite the high prevalence of depression in epileptic patients, this mental disorder continues to be poorly identified by clinicians. To improve this, we have easy-to-apply instruments that routinely screen this patient population and contribute substantially to making the problem more visible and seek to improve the quality of life for this population.

Mechanisms of Psychiatric Comorbidities in Epilepsy

Psychiatric illnesses, including depression and anxiety, are highly comorbid with epilepsy (for review see Josephson and Jetté (Int Rev Psychiatry 29:409-424, 2017), Salpekar and Mula (Epilepsy Behav 98:293-297, 2019)). Psychiatric comorbidities negatively impact the quality of life of patients (Johnson et al., Epilepsia 45:544-550, 2004; Cramer et al., Epilepsy Behav 4:515-521, 2003) and present a significant challenge to treating patients with epilepsy (Hitiris et al., Epilepsy Res 75:192-196, 2007; Petrovski et al., Neurology 75:1015-1021, 2010; Fazel et al., Lancet 382:1646-1654, 2013) (for review see Kanner (Seizure 49:79-82, 2017)). It has long been acknowledged that there is an association between psychiatric illnesses and epilepsy. Hippocrates, in the fourth-fifth century B.C., considered epilepsy and melancholia to be closely related in which he writes that "melancholics ordinarily become epileptics, and epileptics, melancholics" (Lewis, J Ment Sci 80:1-42, 1934). The Babylonians also recognized the frequency of psychosis in patients with epilepsy (Reynolds and Kinnier Wilson, Epilepsia 49:1488-1490, 2008). Despite the fact that the relationship between psychiatric comorbidities and epilepsy has been recognized for thousands of years, psychiatric illnesses in people with epilepsy still commonly go undiagnosed and untreated (Hermann et al., Epilepsia 41(Suppl 2):S31-S41, 2000) and systematic research in this area is still lacking (Devinsky, Epilepsy Behav 4(Suppl 4):S2-S10, 2003). Thus, although it is clear that these are not new issues, there is a need for improvements in the screening and management of patients with psychiatric comorbidities in epilepsy (Lopez et al., Epilepsy Behav 98:302-305, 2019) and progress is needed to understand the underlying neurobiology contributing to these comorbid conditions. To that end, this chapter will raise awareness regarding the scope of the problem as it relates to comorbid psychiatric illnesses and epilepsy and review our current understanding of the potential mechanisms contributing to these comorbidities, focusing on both basic science and clinical research findings.

Cognition, Behavior, and Psychosocial Effects of Seizures in the Developing Brain

Epilepsy, a complex neurological disorder of recurrent seizures, is associated with significant impacts on the developing brain. Patients commonly face multiple comorbidities, including debilitating effects on cognition, behavior, and psychiatric outcomes. These conditions can be a source of great distress for patients that may even be greater than the burden of epilepsy itself. Here we investigate the relationship between seizures and the development of these comorbidities, specifically cognition, memory, learning, behavior, and psychiatric disorders. We first delineate the current research methodology in clinical and basic science that is employed to study the impact of epilepsy and seizures. We then explore neurobiological mechanisms underlying the development of seizures and cognitive and behavioral outcomes. Potential avenues of intervention to best support individuals and optimize their neurodevelopmental progress are also highlighted.

Can we and should we use animal models to study neurobehavioral comorbidities of epilepsy?

Animal systems have been widely used to examine mechanisms of neurobehavioral comorbidities of epilepsy and to help in developing their effective therapies. Despite the progress made in the field, animal studies have their limitations stemming both from issues with modeling neuropsychiatric disorders in the laboratory and from drawbacks of animal models of epilepsy themselves. This review discusses advantages and weaknesses of experimental paradigms and approaches used to model and to analyze neurobehavioral comorbidities of epilepsy, from the perspectives of their needs, interpretation, ways of improvement, and clinical relevance. Developmental studies are required to adequately address age-specific aspects of the comorbidities. The deployment of preclinical Common Data Elements (pCDEs) for epilepsy research should facilitate the standardization and the harmonization of studies in question, while the application of Research Domain Criteria (RDoC) to characterize neurobehavioral disorders in animals with epilepsy should help in closing the bench-to-bedside gap. Special Issue: Epilepsy & Behavior's 20th Anniversary.

The psychopharmacology of epilepsy

Epilepsy affects 1% of the world's population and is defined as two or more unprovoked seizures. Psychiatric conditions (depression, psychosis, anxiety, and attention deficit hyperactivity disorder (ADHD)) may coexist and are linked to negative seizure outcomes and poorer quality of life. There is an increasing body of evidence to suggest a bidirectional relationship between epilepsy and psychiatric disorders, which may imply shared pathophysiologic mechanisms. Extensive research has examined neurobiologic and neuroanatomic substrates for this association revealing some interesting similarities. Psychiatric disorders in people with epilepsy often go underdiagnosed and undertreated, due to fears of exacerbating psychiatric symptoms or provoking seizures, which may cause delays in optimal management. This chapter covers psychiatric conditions in epilepsy largely focusing on depressive disorders and psychotic disorders. Anxiety and ADHD in association with epilepsy are also discussed. Epidemiology, pathophysiologic mechanisms, and pharmacotherapies used to treat epilepsy and psychiatric disorders are also covered.

An animal model of genetic predisposition to develop acquired epileptogenesis: The FAST and SLOW rats

Epidemiological data and gene association studies suggest a genetic predisposition to developing epilepsy after an acquired brain insult, such as traumatic brain injury. An improved understanding of genetic determinants of vulnerability is imperative for early disease diagnosis and prognosis prediction, with flow-on benefits for the development of targeted antiepileptogenic treatments as well as optimal clinical trial design. In the laboratory, one approach to investigate why some individuals are more vulnerable to acquired epilepsy than others is to examine unique rodent models exhibiting either vulnerability or resistance to epileptogenesis. This review focuses on the most well-characterized of these models, the FAST (seizure-prone) and SLOW (seizure-resistant) rat strains, which were derived by selective breeding for differential amygdala electrical kindling rates. We describe how these strains differ in their seizure profiles, neuroanatomy, and neurobehavioral phenotypes, both at baseline and after a brain insult, with this knowledge proving fruitful to identify common pathological abnormalities associated with seizure susceptibility and psychiatric comorbidities. It is important to note that accruing data on strain differences in multiple biological processes provides insight into why some individuals may be more vulnerable to epileptogenesis, although future studies are evidently needed to identify the precise molecular and genetic risk factors. Together, the FAST and SLOW rat strains, and other similar experimental models, are invaluable neurobiological tools to investigate the effect of genetic background on acquired epilepsy risk, as well as the poorly understood relationship between epilepsy development and associated comorbidities.

Effects of Single Cage Housing on Stress, Cognitive, and Seizure Parameters in the Rat and Mouse Pilocarpine Models of Epilepsy

Many experimental approaches require housing rodents in individual cages, including in epilepsy research. However, rats and mice are social animals; and individual housing constitutes a stressful situation. The goal of the present study was to determine the effects of individual housing as compared to conditions maintaining social contact on stress markers and epilepsy. Control male mice socially housed during pretest and then transferred to individual cages for six weeks displayed anhedonia, increased anxiety and biological markers of stress as compared to pretest values or mice kept socially housed during six weeks. Pilocarpine (pilo)-treated mice housed together showed increased levels of anhedonia, anxiety and stress markers as well as decreased cognitive performance as compared to the control group. The differences were more significant in pilo-treated mice housed individually. Anxiety correlated linearly with cognitive performance and stress markers independently of the experimental conditions. In the male rat pilo model, seizures were sixteen times more frequent in singly housed animals as compared to animals kept in pairs. Daily interactions with an experimenter in otherwise singly housed animals was sufficient to produce results identical to those found in animals kept in pairs. We propose that social isolation produces a severe phenotype in terms of stress and seizure frequency as compared to animals maintaining social contact (at least in these two models), a factor that needs to be taken into account for data interpretation, in particular for preclinical studies.

Febrile seizures and increased stress sensitivity in children: How it relates to seizure characteristics

BACKGROUND

Studies suggest that the relationship between seizures and stress starts early in life. However, evidence of long-term altered stress reactivity following early-life seizures is lacking. Our objectives were to assess alterations in stress hormone reactivity in children with past febrile seizures (FS) and investigate how these alterations relate to clinical characteristics.

METHOD

This case-control study compared a convenience sample of children with simple FS (n = 24), complex FS (n = 18), and matched healthy controls (n = 42). Stress was induced by electrode placement for an electroencephalography (EEG) exam. Salivary cortisol to stress, using three samples collected before and after the stressor, was compared between groups and sex. The relationship between stress reactivity and clinical characteristics (i.e., FS duration, age at first FS, time since the last FS) was investigated.

RESULTS

Cortisol reactivity to stress was significantly different depending on study groups, F(1, 78) = 6.415, p = 0.003, η²_p = 0.141, but not sex nor was there a significant interaction between group and sex (p ≥ 0.581). Participants with simple FS showed higher cortisol reactivity to stress (M = 14.936, Standard deviation (SD) = 26.852) compared with those with complex FS (M = -4.663, SD = 18.649, p = 0.015) and controls (M = -3.817, SD = 18.907, p = 0.003). There was no significant difference between participants with complex FS and controls (p > 0.999). Stress reactivity was not linked to clinical characteristics.

CONCLUSIONS

Children with past simple FS showed greater changes in salivary cortisol following stress, suggesting enhanced stress sensitivity. As similar results were not found in a population with complex FS, our study shows that stress alterations are not caused by seizure severity. Future studies are needed to investigate whether stress sensitivity may be premorbid to simple FS and may contribute to simple FS incidence.

Bidirectional relations among common psychiatric and neurologic comorbidities and epilepsy: Do they have an impact on the course of the seizure disorder?

The treatment of epilepsy is not limited to the achievement of a seizure‐free state. It must also incorporate the management of common psychiatric and neurologic comorbidities, affecting on average between 30 and 50% of patients with epilepsy, which have a significant impact on their lives at various levels, including quality of life and the prognosis of the seizure disorder. Mood and anxiety disorders are the most frequent psychiatric comorbidities, whereas stroke and migraine are among the more common neurologic comorbidities, migraine among the younger patients and stroke among the older patients. Not only do these psychiatric and neurologic comorbidities each have a bidirectional relation with epilepsy, but primary mood disorders have a bidirectional relation with these 2 neurologic disorders. Furthermore, depression and migraine have been each associated with a more severe epilepsy course, whereas depression has been associated with a more severe course of stroke and migraines. The purpose of this article is to review the clinical implications of the complex relations among epilepsy and these 3 comorbid disorders, and to identify any clinical and/or experimental evidence that may suggest that having more than one of these comorbid disorders may increase the risk of and course of epilepsy.

A companion to the preclinical common data elements on neurobehavioral comorbidities of epilepsy: a report of the TASK3 behavior working group of the ILAE/AES Joint Translational Task Force

The provided companion has been developed by the Behavioral Working Group of the Joint Translational Task Force of the International League Against Epilepsy (ILAE) and the American Epilepsy Society (AES) with the purpose of assisting the implementation of Preclinical Common Data Elements (CDE) for studying and for reporting neurobehavioral comorbidities in rodent models of epilepsy. Case Report Forms (CRFs) are provided, which should be completed on a per animal/per test basis, whereas the CDEs are a compiled list of the elements that should be reported. This companion is not designed as a list of recommendations, or guidelines for how the tests should be run-rather, it describes the different types of assessments, and highlights the importance of rigorous data collection and transparency in this regard. The tests are divided into 7 categories for examining behavioral dysfunction on the syndrome level: deficits in learning and memory; depression; anxiety; autism; attention deficit/hyperactivity disorder; psychosis; and aggression. Correspondence and integration of these categories into the National Institute of Mental Health (NIMH) Research Domain Criteria (RDoC) is introduced. Developmental aspects are addressed through the introduction of developmental milestones. Discussion includes complexities, limitations, and biases associated with neurobehavioral testing, especially when performed in animals with epilepsy, as well as the importance of rigorous data collection and of transparent reporting. This represents, to our knowledge, the first such resource dedicated to preclinical CDEs for behavioral testing of rodents.

Targeting the Mouse Ventral Hippocampus in the Intrahippocampal Kainic Acid Model of Temporal Lobe Epilepsy

Here we describe a novel mouse model of temporal lobe epilepsy (TLE) that moves the site of kainate injection from the rodent dorsal hippocampus (corresponding to the human posterior hippocampus) to the ventral hippocampus (corresponding to the human anterior hippocampus). We compare the phenotypes of this new model—with respect to seizures, cognitive impairment, affective deficits, and histopathology—to the standard dorsal intrahippocampal kainate model. Our results demonstrate that histopathological measures of granule cell dispersion and mossy fiber sprouting maximize near the site of kainate injection. Somewhat surprisingly, both the dorsal and ventral models exhibit similar spatial memory impairments in addition to similar electrographic and behavioral seizure burdens. In contrast, we find a more pronounced affective (anhedonic) phenotype specifically in the ventral model. These results demonstrate that the ventral intrahippocampal kainic acid model recapitulates critical pathologies of the dorsal model while providing a means to further study affective phenotypes such as depression in TLE.

Different behavioral and pathological changes between epilepsy-associated depression and primary depression models

PURPOSE

Comorbid depression is common in patients with epilepsy. However, the epilepsy-associated depression is generally atypical and has not been fully recognized by neurologists. This study aimed to compare the behavioral and pathological changes between the chronic lithium chloride-pilocarpine rat epilepsy model (Licl-pilocarpine model) and the Chronic Unpredictable Mild Stress rat depression model (CUMS model), to evaluate for differences between epilepsy-associated depression and primary depression.

METHODS

The Licl-pilocarpine model and the CUMS model were established respectively and simultaneously. Spontaneous seizures were recorded by video monitoring. Forced swim test (FST) and sucrose consumption test (SCT) were performed to test depressive behaviors. Immobility time (IMT) and climbing time (CMT) in FST, sucrose preference rate (SPR) in SCT, and weight gain rate (WGR) were adopted to represent severity of depressive behaviors in rats. Immunofluorescent staining was conducted to measure expressions of neuronal specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), and cluster of differentiation molecule 11b (CD11b) in the hippocampus of Licl-pilocarpine model, CUMS model, and Control group.

RESULTS

Significantly, more prolonged IMT was observed in both the Licl-pilocarpine model (p<0.05) and the CUMS model (p<0.01) than Control group. But decreased WGR was only seen in the CUMS model. The percentage of rats with CMT greater than 100s was significantly higher in the Licl-pilocarpine model than the CUMS model (p<0.05). Increased CMT was observed in the Licl-pilocarpine model with mild depression subgroup (EMD, IMT≤100s) even compared with the Control group. Neuronal loss was both found in the Licl-pilocarpine model and the CUMS model when comparing with the Control group (p<0.05). However, the number of GFAP and CD11b staining cells was both greater in the Licl-pilocarpine model than the CUMS model and the Control group (p<0.05).

CONCLUSION

There were some different depressive behavioral and hippocampal pathological changes between the Licl-pilocarpine and the CUMS models except for some common features. Gliosis and microglial activation might be more involved in the pathophysiology of epilepsy-associated depression than primary depression.

Functional disruption of stress modulatory circuits in a model of temporal lobe epilepsy

Clinical data suggest that the neuroendocrine stress response is chronically dysregulated in a subset of patients with temporal lobe epilepsy (TLE), potentially contributing to both disease progression and the development of psychiatric comorbidities such as anxiety and depression. Whether neuroendocrine dysregulation and psychiatric comorbidities reflect direct effects of epilepsy-related pathologies, or secondary effects of disease burden particular to humans with epilepsy (i.e. social estrangement, employment changes) is not clear. Animal models provide an opportunity to dissociate these factors. Therefore, we queried whether epileptic mice would reproduce neuroendocrine and behavioral changes associated with human epilepsy. Male FVB mice were exposed to pilocarpine to induce status epilepticus (SE) and the subsequent development of spontaneous recurrent seizures. Morning baseline corticosterone levels were elevated in pilocarpine treated mice at 1, 7 and 10 weeks post-SE relative to controls. Similarly, epileptic mice had increased adrenal weight when compared to control mice. Exposure to acute restraint stress resulted in hypersecretion of corticosterone 30 min after the onset of the challenge. Anatomical analyses revealed reduced Fos expression in infralimbic and prelimbic prefrontal cortex, ventral subiculum and basal amygdala following restraint. No differences in Fos immunoreactivity were found in the paraventricular nucleus of the hypothalamus, hippocampal subfields or central amygdala. In order to assess emotional behavior, a second cohort of mice underwent a battery of behavioral tests, including sucrose preference, open field, elevated plus maze, 24h home-cage monitoring and forced swim. Epileptic mice showed increased anhedonic behavior, hyperactivity and anxiety-like behaviors. Together these data demonstrate that epileptic mice develop HPA axis hyperactivity and exhibit behavioral dysfunction. Endocrine and behavioral changes are associated with impaired recruitment of forebrain circuits regulating stress inhibition and emotional reactivity. Loss of forebrain control may underlie pronounced endocrine dysfunction and comorbid psychopathologies seen in temporal lobe epilepsy.

Facilitation of kindling epileptogenesis by chronic stress may be mediated by intestinal microbiome

There has been growing interest in the role of intestinal microbiome in brain disorders. We examined whether dysbiosis can predispose to epilepsy. The study was performed in female and male Sprague‐Dawley rats. To induce dysbiosis, the rats were subjected to chronic restraint stress (two 2‐h long sessions per day, over 2 weeks). Cecal content from stressed and sham‐stressed donors was transplanted via oral gavage to recipients, in which commensal microbiota had been depleted by the antibiotics. The study included the following groups: (1) Sham stress, no microbiota transplant; (2) Stress, no microbiota transplant; (3) Sham‐stressed recipients transplanted with microbiota from sham‐stressed donors; (4) Stressed recipients transplanted with microbiota from sham‐stressed donors; (5) Sham‐stressed recipients transplanted with microbiota from stressed donors; and (6) Stressed recipients transplanted with microbiota from stressed donors. After microbiota transplant, all animals were subjected to kindling of the basolateral amygdala. Both chronic stress and microbiome transplanted from stressed to sham‐stressed subjects accelerated the progression and prolonged the duration of kindled seizures. Microbiome from sham‐stressed animals transplanted to chronically stressed rats, counteracted proepileptic effects of restraint stress. These findings directly implicate perturbations in the gut microbiome, particularly those associated with chronic stress, in the increased susceptibility to epilepsy.

Seizure-induced activation of the HPA axis increases seizure frequency and comorbid depression-like behaviors

Our laboratory recently demonstrated that seizures activate the hypothalamic-pituitary-adrenal (HPA) axis, increasing circulating levels of corticosterone (O'Toole et al., 2013). Given the well-established proconvulsant actions of corticosterone, we hypothesized that seizure-induced activation of the HPA axis may contribute to future seizure susceptibility. Further, since hypercortisolism is associated with depression, we propose that seizure-induced activation of the HPA axis may contribute to comorbid depression and epilepsy. To test this hypothesis, we generated mice lacking the GABAA receptor (GABAAR) δ subunit specifically in corticotropin-releasing hormone (CRH) neurons (Gabrd/Crh mice), which exhibit hyporeactivity of the HPA axis (Lee et al., 2014). Gabrd/Crh mice exhibit blunted seizure-induced elevations in corticosterone, establishing a useful tool to investigate the contribution of HPA axis dysfunction on epilepsy and associated comorbidities. Interestingly, Gabrd/Crh mice exhibit decreased acute seizure susceptibility following kainic acid (KA) administration. Furthermore, chronically epileptic Gabrd/Crh mice exhibit a decrease in both spontaneous seizure frequency and depression-like behaviors compared with chronically epileptic Cre^-/- littermates. Seizure susceptibility and associated depression-like behaviors can be restored to wild type levels by treating Gabrd/Crh mice with exogenous corticosterone. Similarly, chemogenetic activation of CRH neurons in the paraventricular nucleus (PVN) is sufficient to increase seizure susceptibility; whereas, chemogenetic inhibition of CRH neurons in the PVN of the hypothalamus is sufficient to decrease seizure susceptibility and depression-like behaviors in chronically epileptic mice. These data suggest that seizure-induced activation of the HPA axis promotes seizure susceptibility and comorbid depression-like behaviors, suggesting that the HPA axis may be a novel target for seizure control.

Kindling epileptogenesis and panic-like behavior: Their bidirectional connection and contribution to epilepsy-associated depression

Anxiety is one of the most common comorbidities of epilepsy, which has major detrimental effects on the quality of life. Generalized anxiety disorder (GAD) associated with epilepsy has been receiving most attention. However, several other forms of anxiety reportedly present in patients with epilepsy, including panic disorder (PD). In this study, using an animal model of limbic epilepsy, we examined the interplay between epilepsy and panic-like behavior (PLB). Further, considering the high degree of comorbidity between depression on the one hand, and both epilepsy and PD on the other hand, we studied whether and how the presence of PLB in animals with epilepsy would affect their performance in depression-relevant tests. Fifty-day-old male Wistar rats were subjected to repeated alternating electrical stimulations of the basolateral amygdala (BLA) to induce kindling of limbic seizures, and the dorsal periaqueductal gray (DPAG) to induce panic-like episodes. Seizure susceptibility and panic reaction threshold were examined before the first and 24h after the last stimulation. At the end of the stimulations, the rats were examined in depression-relevant tests: saccharin preference test (SPT) for anhedonia and forced swimming test (FST) for despair/hopelessness. With regard to kindling, BLA+DPAG stimulation induced more profound increase of seizure susceptibility than BLA stimulation alone (evident as the reduction of the afterdischarge threshold and the increase of the afterdischarge duration). With regard to PLB, the BLA+DPAG stimulation exacerbated the severity of panic-like episodes, as compared with the DPAG stimulation alone. Basolateral amygdala stimulation alone had no effects on panic-like reactions, and DPAG stimulation alone did not modify kindling epileptogenesis. Combined stimulation of BLA and DPAG induced depressive-like behavioral impairments. This is the first experimental study showing bidirectional, mutually exacerbating effect of epilepsy and PLB, and the precipitation of depressive-like state by the epilepsy-PLB comorbidity.