Thalamocortical circuits in generalized epilepsy: Pathophysiologic mechanisms and therapeutic targets

Endoplasmic reticulum stress produced by Thapsigargin affects the occurrence of spike-wave discharge by modulating unfolded protein response pathways and activating immune responses in a dose-dependent manner

The Endoplasmic Reticulum (ER) is associated with many cellular functions, from post-transcriptional modifications to the proper folding of proteins, and disruption of these functions causes ER stress. Although the relationship between epileptic seizures and ER stress has been reported, the contribution of ER stress pathways to epileptogenesis is still unclear. This study aimed to investigate the possible effects of ER stress-related molecular pathways modulated by mild- and high-dose Thapsigargin (Tg) on absence epileptic activity, CACNA1H and immune responses in WAG/Rij rats. For this purpose, rats were divided into four groups; mild-dose (20 ng) Tg, high-dose (200 ng) Tg, saline, and DMSO and drugs administered intracerebroventriculary. EEG activity was recorded for 1 h and 24 h after drug administration following the baseline recording. In cortex and thalamus tissues, GRP78, ERp57, GAD153 protein changes (Western Blot), Eif2ak3, XBP-1, ATF6, CACNA1H mRNA expressions (RT-PCR), NF-κB and TNF-α levels (ELISA) were measured. Mild-dose-Tg administration resulted in increased spike-wave discharge (SWD) activity at the 24th hour compared to administration of saline, and high-dose-Tg and it also significantly increased the amount of GRP78 protein, the expression of Eif2ak3, XBP-1, and CACNA1H mRNA in the thalamus tissue. In contrast, high-dose-Tg administration suppressed SWD activity and significantly increased XBP-1 and ATF6 mRNA expression in the thalamus, and increased NF-κB and TNF-α levels. In conclusion, our findings indicate that Tg affects SWD occurrence by modulating the unfolded protein response pathway and activating inflammatory processes in a dose-dependent manner.

Idiopathic Generalized Epilepsy: Misunderstandings, Challenges, and Opportunities

The idiopathic generalized epilepsies (IGE) make up a fifth of all epilepsies, but <1% of epilepsy research. This skew reflects misperceptions: diagnosis is straightforward, pathophysiology is understood, seizures are easily controlled, epilepsy is outgrown, morbidity and mortality are low, and surgical interventions are impossible. Emerging evidence reveals that patients with IGE may go undiagnosed or misdiagnosed with focal epilepsy if EEG or semiology have asymmetric or focal features. Genetic, electrophysiologic, and neuroimaging studies provide insights into pathophysiology, including overlaps and differences from focal epilepsies. IGE can begin in adulthood and patients have chronic and drug-resistant seizures. Neuromodulatory interventions for drug-resistant IGE are emerging. Rates of psychiatric and other comorbidities, including sudden unexpected death in epilepsy, parallel those in focal epilepsy. IGE is an understudied spectrum for which our diagnostic sensitivity and specificity, scientific understanding, and therapies remain inadequate.

Exploring shared triggers and potential etiopathogenesis between migraine and idiopathic/genetic epilepsy: Insights from a multicenter tertiary-based study

INTRODUCTION

Migraine and epilepsy are two episodic disorders that share common pathophysiological mechanisms. The aim of our research was to assess the possible shared etiopathogenesis by analyzing the relations of headache, and seizure triggers, based on information obtained from a national cohort surveying the headache characteristics of 809 patients who had been diagnosed with idiopathic/genetic epilepsy.

MATERIAL AND METHODS

Our study utilized data from a multi-center, nationwide investigation of headaches in 809 patients with idiopathic/genetic epilepsy. Out of these, 508 patients reported complaints related to any type of headache (333 Migraines, 175 Headaches of other types). In the initial phase of the study encompassing the entire sample of 809 epilepsy patients, differences in seizure triggers were assessed between the migraine group (n = 333) and the non-migraine group (n = 476). Additionally, the subsequent part of the study pertains to a subgroup of the entire patient group, namely those affected by all types of headaches (n = 508), and differences in headache triggers were assessed among migraine patients (n = 333) and those with other types of headaches (n = 175). Similar differences were observed between epilepsy patients with and without a family history of epilepsy.

RESULTS

The most frequently reported seizure triggers in all I/GE group (n = 809) were stress (23%), sleep deprivation (22%) and fatigue (18%), respectively. The most frequently reported headache triggers in migraine patients were stress (31%), sleep deprivation (28%), and noise (26%). The occurrence of menstruation-triggered seizures in individuals with migraine and I/GE was found to be considerably higher than those without migraine. The most common triggers for seizure and headache among the individuals with a positive family history of epilepsy were determined to be light stimuli and sleep deprivation.

CONCLUSION

In conclusion, our study provides valuable insights into the overlapping triggers including sleep patterns, stress levels, and menstrual cycles, etc. and potential shared etiology of migraine and I/GE. Recognizing these connections may facilitate the development of more precise therapeutic strategies and underscore the significance of adopting a holistic, multidisciplinary approach to the management of these intricate neurological conditions. Further research is essential to explore in greater depth the shared mechanisms underpinning these associations and their implications for clinical practice.

Cognitive comorbidities of experimental absence seizures are independent of anxiety

Typical absence seizures (ASs) are brief periods of lack of consciousness, associated with 2.5-4 Hz spike-wave discharges (SWDs) in the EEG, which are highly prevalent in children and teenagers. The majority of probands in these young epileptic cohorts show neuropsychological comorbidities, including cognitive, memory and mood impairments, even after the seizures are pharmacologically controlled. Similar cognition and memory deficits have been reported in different, but not all, genetic animal models of ASs. However, since these impairments are subtle and highly task-specific their presence may be confounded by an anxiety-like phenotype and no study has tested anxiety and memory in the same animals. Moreover, the majority of studies used non-epileptic inbred animals as the only control strain and this may have contributed to a misinterpretation of these behavioural results. To overcome these issues, here we used a battery of behavioural tests to compare anxiety and memory in the same animals from the well-established inbred model of Genetic Absence Epilepsy Rats from Strasbourg (GAERS), their inbred strain of Non-Epileptic Control (NEC) strain (that lack ASs) and normal outbred Wistar rats. We found that GAERS do not exhibit increased anxiety-like behavior and neophobia compared to both NEC and Wistar rats. In contrast, GAERS show decreased spontaneous alternation, spatial working memory and cross-modal object recognition compared to both NEC and Wistar rats. Furthermore, GAERS preferentially used egocentric strategies to perform spatial memory tasks. In summary, these results provide solid evidence of memory deficits in GAERS rats that do not depend on an anxiety or neophobic phenotype. Moreover, the presence of differences between NEC and Wistar rats stresses the need of using both outbred and inbred control rats in behavioural studies involving genetic models of ASs.

Patient-derived SLC6A1 variant S295L results in an epileptic phenotype similar to haploinsufficient mice

The solute carrier family 6 member 1 (SLC6A1) gene encodes GAT-1, a γ-aminobutyric acid transporter expressed on astrocytes and inhibitory neurons. Mutations in SLC6A1 are associated with epilepsy and developmental disorders, including motor and social impairments, but variant-specific animal models are needed to elucidate mechanisms. Here, we report electrocorticographic (ECoG) recordings and clinical data from a patient with a variant in SLC6A1 that encodes GAT-1 with a serine-to-leucine substitution at amino acid 295 (S295L), who was diagnosed with childhood absence epilepsy. Next, we show that mice bearing the S295L mutation (GAT-1S295L/+ ) have spike-and-wave discharges with motor arrest consistent with absence-type seizures, similar to GAT-1+/- mice. GAT-1S295L/+ and GAT-1+/- mice follow the same pattern of pharmacosensitivity, being bidirectionally modulated by ethosuximide (200 mg/kg ip) and the GAT-1 antagonist NO-711 (10 mg/kg ip). By contrast, GAT-1-/- mice were insensitive to both ethosuximide and NO-711 at the doses tested. In conclusion, ECoG findings in GAT-1S295L/+ mice phenocopy GAT-1 haploinsufficiency and provide a useful preclinical model for drug screening and gene therapy investigations.