Failure to detect association between polymorphisms of the sodium channel gene SCN1A and febrile seizures in Chinese patients with epilepsy

Association between SCN1A polymorphism and risk of epilepsy in children: A systematic review and meta-analysis

Epilepsy is a common neurological disorder in children. Numerous studies have demonstrated the association between SCN1A polymorphisms and risk of epilepsy in adults, but their role in epilepsy in children has just gained traction and results have remained inconsistent. In this work, we performed a systematic review and meta-analysis to assess the association between SCN1A polymorphisms and risk for epilepsy in children. A systematic literature search was performed in PubMed, Scopus, Web of Science, China National Knowledge Internet, Wanfang and VIP databases to identify eligible studies up to June 2023. Quantitative data synthesis was then performed under five genetic models: dominant, recessive, homozygous, heterozygous, and allele. Five studies involving 1380 subjects were included in the meta-analysis. Among many SCN1A polymorphisms reported, only rs2298771 was repeatedly studied in these reports. Pooled analysis demonstrated that there was no significant association between the polymorphism and risk of epilepsy in children (P>0.05). In conclusion, SCN1A rs2298771 polymorphism was not significantly associated with the risk of epilepsy in children.

The long-term neurodevelopmental outcomes of febrile seizures and underlying mechanisms

Febrile seizures (FSs) are convulsions caused by a sudden increase in body temperature during a fever. FSs are one of the commonest presentations in young children, occurring in up to 4% of children between the ages of about 6 months and 5 years old. FSs not only endanger children's health, cause panic and anxiety to families, but also have many adverse consequences. Both clinical and animal studies show that FSs have detrimental effects on neurodevelopment, that cause attention deficit hyperactivity disorder (ADHD), increased susceptibility to epilepsy, hippocampal sclerosis and cognitive decline during adulthood. However, the mechanisms of FSs in developmental abnormalities and disease occurrence during adulthood have not been determined. This article provides an overview of the association of FSs with neurodevelopmental outcomes, outlining both the underlying mechanisms and the possible appropriate clinical biomarkers, from histological changes to cellular molecular mechanisms. The hippocampus is the brain region most significantly altered after FSs, but the motor cortex and subcortical white matter may also be involved in the development disorders induced by FSs. The occurrence of multiple diseases after FSs may share common mechanisms, and the long-term role of inflammation and γ-aminobutyric acid (GABA) system are currently well studied.

Levetiracetam Modulates EEG Microstates in Temporal Lobe Epilepsy

To determine the effects of Levetiracetam (LEV) therapy using EEG microstates analysis in a population of newly diagnosed Temporal Lobe Epilepsy (TLE) patients. We hypothesized that the impact of LEV therapy on the electrical activity of the brain can be globally explored using EEG microstates. Twenty-seven patients with TLE were examined. We performed resting-state microstate EEG analysis and compared microstate metrics between the EEG performed at baseline (EEG_pre) and after 3 months of LEV therapy (EEG_post). The microstates A, B, C and D emerged as the most stable. LEV induced a reduction of microstate B and D mean duration and occurrence per second (p < 0.01). Additionally, LEV treatment increased the directional predominance of microstate A to C and microstate B to D (p = 0.01). LEV treatment induces a modulation of resting-state EEG microstates in newly diagnosed TLE patients. Microstates analysis has the potential to identify a neurophysiological indicator of LEV therapeutic activity. This study of EEG microstates in people with epilepsy opens an interesting path to identify potential LEV activity biomarkers that may involve increased neuronal inhibition of the epileptic network.

Global and intertuberal epileptic networks in tuberous sclerosis based on stereoelectroencephalographic (sEEG) findings: a quantitative EEG analysis in pediatric subjects and surgical implications

OBJECTIVE

Recent evidence favors a network concept in tuberous sclerosis (TSC) with seizure generation and propagation related to changes in global and regional connectivity between multiple, anatomically distant tubers. Direct exploration of network dynamics in TSC has been made possible through intracranial sampling with stereoelectroencephalography (sEEG). The objective of this study is to define epileptic networks in TSC using quantitative analysis of sEEG recordings. We also discuss the impact of the definition of these epileptic networks on surgical decision-making.

METHODS

Intracranial sEEG recordings were obtained from four pediatric patients who presented with medically refractory epilepsy secondary to TSC and subjected to quantitative signal analysis methods. Cortical connectivity was quantified by calculating pairwise coherence between all contacts and constructing an association matrix. The global coherence, defined as the ratio of the largest eigenvalue to the sum of all the eigenvalues, was calculated for each frequency band (delta, theta, alpha, beta, gamma). Spatial distribution of the connectivity was identified by plotting the leading principal component (product of the largest eigenvalue and its corresponding eigenvector).

RESULTS

Four pediatric subjects with TSC underwent invasive intracranial monitoring with sEEG, comprising 31 depth electrodes and 250 contacts, for localization of the epileptogenic focus and guidance of subsequent surgical intervention. Quantitative connectivity analysis revealed a change in global coherence during the ictal period in the beta/low gamma (14-30 Hz) and high gamma (31-80 Hz) bands. Our results corroborate findings from existing literature, which implicate higher frequencies as a driver of synchrony and desynchrony.

CONCLUSIONS

Coordinated high-frequency activity in the beta/low gamma and high gamma bands among spatially distant sEEG define the ictal period in TSC. This time-dependent change in global coherence demonstrates evidence for intra-tuberal and inter-tuberal connectivity in TSC. This observation has surgical implications. It suggests that targeting multiple tubers has a higher chance of seizure control as there is a higher chance of disrupting the epileptic network. The use of laser interstitial thermal therapy (LITT) allowed us to target multiple disparately located tubers in a minimally invasive manner with good seizure control outcomes.

SCN1A IVS5N+5 G>A Polymorphism and Risk of Febrile Seizure and Epilepsy: A Systematic Review and Meta-Analysis

Background: Previous studies had investigated the association between polymorphism of IVS5N+5 G>A in SCN1A and the risk of febrile seizure and epilepsy. However, the results were inconsistent. We aimed to conduct a systematic review and meta-analysis to evaluate the association between SCN1A IVS5N+5 G>A polymorphism and risk of febrile seizures and epilepsy. Methods: We searched Embase, Medline, Scopus, and CNKI for studies on the association between SCN1A IVS5N+5 G>A polymorphism and risk of febrile seizures and epilepsy up to 19 February 2020. We pooled odds ratios (ORs) and 95% confidence intervals (CIs) by different genetic models. To explore the source of heterogeneity, we performed the subgroup analysis by ethnicity and source of control. Results: We included a total of 12 studies in the meta-analysis. We found a significant negative association between G allele SCN1A IVS5N+5 G>A polymorphism, febrile seizures [G vs. A: OR (95% CI): 0.690 (0.530-0.897); GG vs. AA: 0.503 (0.279-0.908); AG vs. AA: 0.581 (0.460-0.733); GG + AG vs. AA: 0.543 (0.436-0.677); AA + GG vs. AG: 1.309 (1.061-1.615)], and epilepsy [G vs. A: 0.822 (0.750-0.902); GG vs. AA: 0.655 (0.515-0.832); AG vs. AA: 0.780 (0.705-0.862); GG vs. AG + AA: 0.769 (0.625-0.947); GG + AG vs. AA: 0.743 (0.663-0.833); AA + GG vs. AG: 1.093 (1.001-1.193)]. The subgroup analysis shows the association varied by type of disease, ethnicity, and source of control. Conclusion: The present meta-analysis suggests that G allele in SCN1A IVS5N+5 G>A polymorphism is a protective factor of febrile seizures and epilepsy. It is possible to determine the vulnerability of each individual to develop febrile seizures or epilepsy genotype by these genetic variants. Future studies with better study designs are needed to confirm the results. Study Registration: This study was registered in the International Prospective register of systematic reviews (PROSPERO, CRD42020163318).

SCN1A variations and response to multiple antiepileptic drugs

In the current study, we have used the haplotype-tagging single-nucleotide polymorphisms (SNPs) to determine associations between genetic variants in SCN1A and treatment response in 519 Caucasian patients with known response status for epilepsy treated with antiepileptic drugs (AEDs) with sodium channel blocking effects. Nine SNPs within SCN1A were genotyped in this cohort. The only association observed was for rs10188577. A greater proportion of drug-resistant patients were heterozygous compared with drug responsive patients (48.3% vs 35.4%, P=0.014). After correction for potential confounding factors, the association for rs10188577 was only marginally significant (P=0.049). In light of our findings, it seems unlikely that rs10188577 could be a major determinant of response to AEDs. However, looking at the influence of rs10188577 on the expressed quantitative trait association patterns within the immediate vicinity of SCN1A, we found significant associations with neighbouring sodium channel genes, SCN7A and SCN9A (P<0.025), which warrants further studies.

Case-control association study of polymorphisms in the voltage-gated sodium channel genes SCN1A, SCN2A, SCN3A, SCN1B, and SCN2B and epilepsy

High-frequency action potentials are mediated by voltage-gated sodium channels, composed of one large α subunit and two small β subunits, encoded mainly by SCN1A, SCN2A, SCN3A, SCN1B, and SCN2B genes in the brain. These play a key role in epilepsy, with the most commonly mutated gene in epilepsy being SCN1A. We examined whether polymorphisms in the above genes affect epilepsy risk in 1,529 epilepsy patients and 1,935 controls from four ethnicities or locations: Malay, Indian, and Chinese, all from Malaysia, and Chinese from Hong Kong. Of patients, 19 % were idiopathic, 42 % symptomatic, and 40 % cryptogenic. We genotyped 43 polymorphisms: 27 in Hong Kong, 28 in Malaysia, and 12 in both locations. The strongest association with epilepsy was rs3812718, or SCN1A IVS5N+5G>A: odds ratio (OR) = 0.85 for allele G (p = 0.0009) and 0.73 for genotype GG versus AA (p = 0.003). The OR was between 0.76 and 0.87 for all ethnicities. Meta-analysis confirmed the association (OR = 0.81 and p = 0.002 for G, and OR = 0.67 and p = 0.007 for GG versus AA), which appeared particularly strong for Indians and for febrile seizures. Allele G affects splicing and speeds recovery from inactivation. Since SCN1A is preferentially expressed in inhibitory neurons, G may decrease epilepsy risk. SCN1A rs10188577 displayed OR = 1.20 for allele C (p = 0.003); SCN2A rs12467383 had OR = 1.16 for allele A (p = 0.01), and displayed linkage disequilibrium with rs2082366 (r (2) = 0.67), whose genotypes tended toward association with SCN2A brain expression (p = 0.10). SCN1A rs2298771 was associated in Indians (OR = 0.56, p = 0.005) and SCN2B rs602594 with idiopathic epilepsy (OR = 0.62, p = 0.002). Therefore, sodium channel polymorphisms are associated with epilepsy.

Effects of SCN1A and GABA receptor genetic polymorphisms on carbamazepine tolerability and efficacy in Chinese patients with partial seizures: 2-year longitudinal clinical follow-up

AIMS

To investigate the tolerability and efficacy of carbamazepine treatment in patients with partial-onset seizures and the association with polymorphisms in the sodium channel α-subunit type 1 (SCN1A), and gamma-aminobutyric acid (GABA) receptor genes among the Chinese Han population.

METHODS

448 patients were genotyped for single nucleotide polymorphisms selected of the SCN1A and GABA-receptor genes. Monotherapy with carbamazepine (CBZ) was administered to the patients. The effectiveness of CBZ treatment was evaluated with regard to efficacy by the decrease in seizures and tolerability by retention rates.

RESULTS

SCN1A rs3812718 A/G with CBZ tolerability (P= 0.038) throughout 24 months of clinical follow-up and the GABRA1 rs2290732 A/G were significantly associated with CBZ tolerability (P= 0.001). The maintenance dose and serum level of CBZ in AA genotype carriers of rs3812718 A/G were significantly higher than those of GG genotype carriers between 3 and 12 months of follow-up. The proportion of AA genotype carriers of rs2298771 A/G with seizure free was significantly higher than that of AG+GG genotype carriers from 3 months to 15 months of follow-up (P < 0.05).

CONCLUSION

rs3812718 A/G and rs2290732 A/G polymorphisms affected the tolerability of CBZ. rs2298771 A/G was associated with efficacy of CBZ treatment.

Genetic contribution to common epilepsies

PURPOSE OF REVIEW

We review key findings over the past year in the genetics of the common epilepsies and consider their impact on the field.

RECENT FINDINGS

There have been important discoveries across two major aspects of genetics of the common epilepsies. Firstly, the first genome-wide association study in epilepsy has been published, for the focal epilepsies. With reasonable power to detect even modest effect sizes, the absence of genome-wide significant association demands refinement of further single-nucleotide polymorphism (SNP)-based genome-wide approaches, with a focus on more homogeneous phenotypes. Secondly, several putatively causal variants of a different type, copy number variants (CNVs), have been discovered. Several recurrent epilepsy-associated CNVs have been identified, including microdeletions at 15q13.3 and 16p13.11. CNVs constitute the commonest known genetic cause of the epilepsies. How CNVs cause disease, and why the same CNV can cause different diseases is unexplained. Nevertheless, CNVs will accelerate discovery of 'epilepsy genes', focussing attention on specific genomic regions. With the published genome-wide SNP study, CNVs are redirecting research efforts to a search for rare variants underlying common epilepsies. CNVs have also highlighted the challenges ahead in genotype-phenotype correlation.

SUMMARY

Major discoveries are reshaping the genetics of the common epilepsies and prefiguring whole exome/whole genome resequencing efforts.