Precision medicine approaches in epilepsy: A systematic review of genetic markers and personalized treatment strategies

Epilepsy is one of the most common neurological diseases globally. We conducted a systematic review of the genetic markers and personalized treatment strategies used in the precision medicine treatment of epilepsy. An exhaustive electronic search was carried out on PubMed and Google Scholar, spanning from inception up to June 2023 on epilepsy and biomarkers. A total of 45 articles from PubMed and 19 articles from Google Scholar were imported and screened based on studies that focused primarily on genetic markers and precision methods for epilepsy subtyping, treatment strategies, outcomes, and adverse effects. Reviews and studies not in English were excluded. Full‐text data extraction, coding, and analysis were carried out with Microsoft Excel. For the risk of bias assessment of the final included studies, the Critical Appraisal Skills Program checklist was used. A total of 19 studies were analyzed in the review. The SLC35A2 gene saw a reduction in seizure frequency with d‐galactose treatment while the KCNQ2 gene saw improvement with phenytoin, carbamazepine, and retigabine. GRIN2D gene saw varying improvements with memantine. KCNT1 gene saw improvement with only a combination of quinidine and topiramate, quinidine was not useful when used alone. Other studies involved the identification of different markers using gene and exome sequencing. These studies collectively provide a diverse range of insights into epilepsy, with variations in study design, sample size, age groups, and diagnostic criteria, highlighting the multifaceted nature of epilepsy research. These studies contribute to our understanding of epilepsy diagnosis and management in different clinical settings, however, there were some limitations such as QT prolongation was observed with specific medications and participant heterogeneity. Small sample sizes reduced statistical power and brief durations of studies limited their ability for long‐term analysis. Although most studies had a low risk of bias, two studies demonstrated some reporting bias. Fianlly, the absence of biomarkers is a limitation that impedes the study's capacity to explore underlying biological mechanisms.

soft Excel.For the risk of bias assessment of the final included studies, the Critical Appraisal Skills Program checklist was used.A total of 19 studies were analyzed in the review.The SLC35A2 gene saw a reduction in seizure frequency with D-galactose treatment while the KCNQ2 gene saw improvement with phenytoin, carbamazepine, and retigabine.GRIN2D gene saw varying improvements with memantine.KCNT1 gene saw improvement with only a combination of quinidine and topiramate, quinidine was not useful when used alone.Other studies involved the identification of different markers using gene and exome sequencing.These studies collectively provide a diverse range of insights into epilepsy, with variations in study design, sample size, age groups, and diagnostic criteria, highlighting the multifaceted nature of epilepsy research.These studies contribute to our understanding of epilepsy diagnosis and management in different clinical settings, however, there were some limitations such as QT prolongation was observed with specific medications and participant heterogeneity.Small sample sizes reduced statistical power and brief durations of studies limited their ability for long-term analysis.Although most studies had a low risk of bias, two studies demonstrated some reporting bias.Fianlly, the absence of biomarkers is a limitation that impedes the study's capacity to explore underlying biological mechanisms.

| INTRODUCTION
Epilepsy is one of the most common neurological diseases globally.It is a chronic non-communicable disease of the brain that affects people of all ages and is characterized by recurrent unprovoked seizures that may involve a part of the body (partial) or the entire body (generalized).
Around 5 million individuals worldwide are affected by epilepsy annually, out of which 60% of people develop epilepsy due to structural causes such as stroke or traumatic brain injuries that initiate epileptogenesis, a process in which brain-damaging injuries begin a cascade of cellular and molecular changes in the epileptogenic brain.At the gene level epileptic brain generates an epigenome that causes histone and DNA structure modification which includes methylation of cytosine, noncoding RNA expression, and posttranslational histone modification, thereby altering gene expression.This process may release and express certain molecules that can be detected as biomolecules in blood/ cerebrospinal fluid analysis, brain tissue analysis, imaging, or electrophysiology.These biomolecules would be used as primary diagnostic biomarkers and for personalized treatment strategies. 1,2cent developments in gene sequencing technology have resulted in several significant breakthroughs.Mutations in the DEPDC5 gene, which encodes a negative regulator of the mammalian target of the rapamycin pathway, were discovered to be a major cause of inherited focal epilepsies.Variations in the SCN1A gene were also shown to enhance vulnerability to temporal lobe epilepsy linked with hippocampal sclerosis and febrile episodes.Furthermore, intellectual impairment and epilepsy are also linked with gain-of-function missense mutations in the SCN8A gene resulting in hyperactivation of Na v 1.6 channel and increased neural firing. 3Several other genes (CDH19, SYNGAP1, TPP1, and PRRT2) thought to be previously obsolete in epilepsy precision therapy were identified with significant diagnostic yield.The finding of pathogenic mutations in TPP1 is crucial, as precision medicine therapy with an enzyme replacement treatment is highly effective. 4Likewise, a very common potassium channel gene in epilepsy, KCNT1, was previously treated with quinidine.However, a recent study demonstrated that quinidine was ineffective in the management of patients with that particular gene. 5Therefore, Identification of such markers is essential as it can also influence clinical decision-making, including antiepileptic drug (AED) selection and consideration of epilepsy surgery, thereby supporting its incorporation in the routine clinical care of this patient group.
Although use of precision medicine in diagnostic and treatment aspects of epilepsy is relatively newer area of exploration, it is important to put the discoveries in this field in a larger perspective.Our study aimed to put the regional innovations in precision medicine field of epilepsy in a broader perspective to understand and correlate the current effective approach in management of epilepsies.There is no such review of precision medicine in epilepsy done before this to correlate the current approach.

| METHODOLOGY
The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were adhered to in this systematic review (Figure A1).The work has been reported in line with AMSTAR (Assessing the methodological quality of systematic reviews) Guidelines.
The protocol was registered on the International Prospective Reg- A rigorous selection process with predefined inclusion and exclusion criteria was applied to ensure high quality.Only those studies were included that investigate the application of precision medicine approaches in epilepsy, focus on role of genetic markers with their role in epilepsy subtyping, prognosis, treatment response or adverse effects and discuss personalized treatment strategies.Review article and studies that were not in English were excluded.PICO was formulated to get concise data.The population for our study were epilepsy patients, intervention was precision medicine approaches based on genetic markers, compared with standard non-precision medicine treatment to assess outcomes like improvement in diagnosis, prognosis, and treatment response.
Articles were imported into Rayyan, where duplicates were removed.The screening of titles and abstracts of all retrieved articles, as well as the removal of those not meeting the inclusion criteria, were independently conducted by four authors (A.A., F.A., M.W., and Z.H.) in groups of two.The full texts of the remaining articles were assessed against the eligibility criteria.Any conflicts or disagreements were deliberated upon and resolved by the corresponding author.
Data extraction was independently carried out by six authors and cross-checked by the corresponding author.The creation of the data extraction sheet in Google Sheets was performed by one author (H.I.).
The information for extraction encompassed study title, year of publication, author names, journal of publication, study design, study duration, sample size, participants' demographics, diagnostic criteria for epilepsy, genetic markers mentioned in the article and their identification methods, genetic subtypes, treatment approaches, primary and secondary outcomes, results, and limitations.Data extraction was independently conducted by A.A., F.A., H.I., M.W., S.O., and Z.H. following this sheet.
The authors independently converted the raw data extracted from the full texts into the coded form.These codes were carefully reviewed by the corresponding author.The codes were analyzed using Microsoft Excel and presented in Figures 1-8.
Our overall approach consisted of two main steps.Initially, we conducted a narrative synthesis of the collected data.Subsequently, we performed a structured analysis using Microsoft Excel.During this analysis, we concentrated on various significant aspects of the studies, which included the study design, age distribution, gender distribution, genetic markers, treatment approaches, and outcomes.To aid in this analysis, we made effective use of Excel's pivot tables for data organization and summarization.In addition, we utilized bar charts to visually illustrate our findings.This combined methodology ensured that our results were presented in a clear and comprehensible manner.
For quality assessment (risk of bias assessment) of the final included studies Critical Appraisal Skills Program (CASP) checklist was used.Randomized control trials, cohort studies, case-control studies, and qualitative types of research were critically assessed by A.A., F.A., M.W., S.O., and Z.H., by following the checklist and CASP guidelines for the aforementioned study type.

| Study characteristics
The included studies vary in terms of their design, sample size, and diagnostic criteria for epilepsy.Among these studies, six were case reports, [6][7][8][9][10][11] each featuring a small sample size or individual cases.In contrast, larger-scale studies inlcuding three cohorts, [12][13][14] five were trials 5,[15][16][17][18] and two were retrospective studies. 19,20One study was prospective study with a smaller sample size, emphasizing a diagnostic approach involving brain MRI. 4 A qualitative study with a sample size of 12, focusing on gender distribution, revealing that males were less than 50% of the participants was also included in this review. 21A case-control study with over 100 participants, relying on a diagnostic approach involving the history of partial seizures and EEG was also a part of this review (Tables 1-3). 22

| Outcomes
Study included a wide variety of studies on the basis of outcomes, a wide range of genetic markers were used and several AEDs were used which showed a remarkable reduction in seizures.

| Reduction in seizure frequency by using different antiepileptics
A trial focusing on the SLC35A2 gene resulting in a reduction in seizure frequency with D-galactose treatment. 15A reported a case report involving the KCNQ2 gene, highlighting a remarkable response to phenytoin (PHT), carbamazepine (CBZ), and retigabine treatment. 6A retrospective study which was a part of this study it involved various genes and resulted a reduction in seizure frequency but no specific treatment was mentioned. 19e trial was conducted focusing on the CYP1A1 gene, using gene sequencing to predict drug responses to phenobarbitone, PHT, CBZ, and valproic acid. 17A case study involving the GRIN2D gene, used memantine for treatment but only one child showed decrease in seizure frequency. 8

| Importance of KCNT1 gene in diagnosis and treatment of epilepsy
Collectively, four studies have offered valuable insights into the role of the KCNT1 gene in epilepsy and potential treatment options.A case in which whole exome sequencing (WES) was employed, revealing that a combination of quinidine and topiramate had a synergistic effect, resulting in improved treatment outcomes. 9In contrast one other study also used clinical exome sequencing to investigate the KCNT1 gene; however, regrettably, the patient's condition did not improve. 10In a separate trial, focused on the KCNT1 gene, and their findings demonstrated that quinidine treatment significantly reduced the frequency of seizures. 5These studies collectively underscore the complexity of genetic epilepsy disorders associated with the KCNT1 gene, highlighting both potential treatment successes and the challenges in managing such conditions.

| Use of different genetic markers in identification of disease and treatment
A case-control study involving the PON1 gene, observing indirect effects of the Q192R genotype on the TLE-PP phenome and highlighting significant total effects of -SH groups. 22case report involving the GRIN2A gene and gene sequencing to identify markers, using memantine for treatment.11 A cohort study centered on the SCN1A gene, employing gene sequencing to detect markers, and utilizing antisense oligonucleotides (ASOs) for treatment.12 In a related context, a prospective study that focused on genes, including SCN1A and utilized WES to identify markers.4 The remaining seven studies did not specify genetic markers, diagnostic methods, treatments, or outcomes in the provided information.7,13,14,16,18,20,21

| Risk of bias assessment
In this study for assessment of bias, we used Critical Appraisal Checklist (CASP) all 19 studies were reported low risk for bias.There might be a possibility of reporting bias.

| DISCUSSION
In a 2023 study led by Serrano et al., 15 the use of D-Galactose was linked to a decrease in seizure occurrences among individuals affected by SLC35A2-related conditions, suggesting a potential therapeutic advantage by improving glycosylation and potentially enhancing the quality of life.Earlier research findings lent support to these conclusions, with half of the participants, who experienced frequent seizures, demonstrating significant improvements, and remaining seizure-free.It is worth emphasizing that a quarter of the population did not exhibit any clinical improvement.However, as the study population was quite small, these findings do not have statistical significance. 23Furthermore, a separate study also reported remarkable improvements in epilepsy associated with this treatment approach, which involves supplying exogenous galactose (specifically galactose-1-phosphate) to bypass the faulty transport system of UDP-galactose, a critical substrate for glycosylation reactions, potentially alleviating symptoms associated with SLC35A2-CDG.However, it is crucial to understand that the use of galactose as a treatment for SLC35A2-CDG is not a cure, and its effectiveness can vary depending on the specific mutations in the SLC35A2 gene in different individuals. 24adori et al. 6 presented a case report involving the KCNQ2 gene, underscoring a remarkable response to treatment with PHT, CBZ, and retigabine.This case highlights the substantial impact of genetic variants on patient management.In the context of KCNQ2 encephalopathy, the study observed that certain AEDs like CBZ and PHT exhibited significant efficacy in controlling seizures, even in neonates with this severe neurological disorder.These drugs are believed to work by modulating voltage-gated sodium channels and potassium channels, which are critical in neuronal function.By effectively regulating these channels, CBZ and PHT can potentially restore normal neuronal excitability, ultimately reducing seizure activity and improving patient outcomes.Early identification and tailored AED treatment are emphasized to optimize the management of KCNQ2 encephalopathy, offering hope for better control of seizures and improved quality of life in affected individuals. 25ese collective research studies have yielded valuable insights into the involvement of the KCNT1 gene in epilepsy and potential treatment options.Kravetz et al. 9 documented a case where they applied WES, revealing that a combination of quinidine and topiramate had a synergistic effect, leading to improved treatment outcomes.Conversely, Madaan et al. 10 also utilized clinical exome sequencing to investigate the KCNT1 gene, but regrettably, the patient's condition did not exhibit any improvement.Despite attempting various medications and a ketogenic diet, the child's condition deteriorated, and they passed away at 9 months of age.In a separate study, Mullen et al. 5 focused on the KCNT1 gene, and their findings  When we compare the findings of Kearney 8 with the previous study that detected GRIN2D mutations and employed memantine treatment, 27 we can discern several important insights and parallels, both studies share a common focus on GRIN2D mutations, highlighting the significance of this gene in the context of epilepsy.In Kearney, 8 two children with GRIN2D mutations were treated with memantine.Interestingly, one of these children experienced a reduction in seizures while the other did not respond to memantine and required alternative seizure management.In contrast, the previous study identified GRIN2D mutations in four patients, and three of them received memantine treatment for intractable epilepsy, resulting in seizure freedom.This suggests that memantine can be an effective treatment option for some individuals with GRIN2D mutations, but it Balestrini et al. 19 Grover et al. 17  Their treatment approach involved the innovative use of ASOs.While specific treatment outcomes were not provided, this study underscores the importance of exploring genetic markers and innovative treatments, such as ASOs, in managing epilepsy associated with the SCN1A gene.Perucca et al. 4 undertook a prospective study encompassing various genes, including SCN1A.They employed advanced WES to identify genetic markers and emphasized the profound impact of genetic variants on patient management.This prospective study, along with the use of WES, significantly contributes to our understanding of the role of genetics in the management of epilepsy.However, several studies 7,13,14,16,18,20,21 did not provide specific details regarding the genes under investigation, diagnostic methods, treatments, or outcomes.Consequently, the significance of these studies remains unclear due to the limited information provided.Nonetheless, the discussed studies collectively demonstrate the ongoing efforts to unravel the complex genetic aspects of epilepsy and explore innovative approaches for its management.
The findings from these studies underscore the critical role of ister of Systematic Reviews (PROSPERO).An exhaustive electronic search was carried out on PubMed and Google Scholar, Cochrane, and Web of Science spanning from inception up to June 2023.The search involved the utilization of relevant MeSH terms and pertinent keywords associated with epilepsy and precision medicine.Keyword searching was performed by multiple authors, and references were explored in both forward and backward directions.The search strategy encompassed a broad spectrum of topics, including precision medicine, genetic markers, genetic testing, pharmacogenomic testing, molecular diagnostic techniques, clinical trials, randomized controlled trials, systematic reviews, epilepsy, seizures, anticonvulsants, pharmacogenetics, electroencephalography, genetic variation, adverse effects, treatment response, prognosis, electrocorticography, implantable neurostimulators, molecular-targeted therapy, and deep brain stimulation.

FuncƟonal
MRI (fMRI) predicts epilepsy, outcome and aids precision medicine geneƟc markers can predict drug response precision medcine will be accepted if caregivers' understanding is increased seizures were increased despite treatment early diagnosis and early therapeuƟc intervenƟon is important Quinidine can be given as it's a KCNT1 channel blocker geneƟc tesƟng for epilepsy helped in making treatment strategies the treatment given decreased seizure frequency Main Findings and Treatment Strategies F I G U R E 3 Results for various treatment strategies.
F I G U R E 4 Efficacy of treatment.help in detecƟng SCN1A genes epilepsy CYP1A1 predicted drug response death geneƟc variants impact on paƟent management improvement of NP measures memanƟne result in seizures reducƟon in 1/2 children F I G U R E 5 Primary outcomes.

7
Genetic markers.indicated that quinidine treatment significantly reduced the frequency of seizures.These studies collectively underscore the complexity of genetic epilepsy disorders linked to the KCNT1 gene, highlighting both potential treatment successes and the challenges in managing such conditions.According to a previous study by Mikati et al., 26 two cases were documented with drug-resistant epilepsy caused by KCNT1 mutations who received quinidine treatment.Both mutations demonstrated increased activity in laboratory testing, resulting in heightened electrical activity, which was alleviated by quinidine.One of these patients, diagnosed with epilepsy of infancy characterized by migrating focal seizures, experienced an 80% reduction in seizure frequency, as recorded in seizure diaries and partially verified through objective T A B L E 1 Study characteristics.
may not universally benefit all patients.The combined results underscore the variability in treatment responses to memantine among individuals with GRIN2D mutations.While some patients demonstrated significant improvements in seizure control with memantine, others did not respond favorably and needed alternative treatment approaches.This highlights the importance of personalized treatment strategies in managing epilepsy cases associated with GRIN2D mutations.Both studies appear to emphasize the clinical significance of occipital epileptic activity among patients with GRIN2D mutations.Occipital epileptic activity was frequently detected in the previous study's patients, and although not explicitly mentioned in Kearney,8 it may imply a specific pattern of epileptic activity associated with GRIN2D mutations relevant for diagnosis and treatment planning.These combined findings reveal the intricacies of epilepsy cases linked to GRIN2D mutations and the variable response to memantine treatment.While memantine appears effective for some individuals with GRIN2D mutations, it may not be equally effective for all, emphasizing the need for individualized treatment strategies.The identification of occipital epileptic activity in these cases may serve as a diagnostic marker.Further research is warranted to gain a deeper understanding of the factors influencing treatment responses and to develop tailored approaches for managing epilepsy related to GRIN2D mutations.Balestrini et al.19 conducted a retrospective study to investigate the genetic aspects of epilepsy management.In this study, the researchers examined various genes associated with epilepsy, although the specific genes and their variants were not detailed in the provided information.The primary outcome reported in this retrospective study was a reduction in seizure frequency among the study participants.However, the study did not specify the treatments or interventions that led to this reduction in seizure frequency.Despite the lack of detailed treatment information, this study highlights the potential role of genetics in influencing the outcomes of epilepsy management.The reduction in seizure frequency suggests that genetic factors may play a significant role in how individuals respond to treatments or medications.Nevertheless, the specific genes involved and the mechanisms by which they influence treatment outcomes remain unclear due to the limited information provided by genetic information in tailoring epilepsy treatment, enhancing patient outcomes, and optimizing epilepsy care.Identifying specific genetic variants empowers clinicians to personalize treatment approaches, increasing the likelihood of improved outcomes for individual patients.This highlights the urgent need to integrate genetic testing into the standard practice of epilepsy diagnosis and treatment planning, ensuring that patients receive the most effective and tailored interventions.However, the studies also reveal a crucial need for more comprehensive reporting in epilepsy research.Several investigations lacked essential details regarding genes, diagnostic methods, treatments, and outcomes.To maximize the potential of genetics in epilepsy management, future research must prioritize thorough documentation and reporting.Furthermore, these collective findings emphasize the necessity of continued research in epilepsy genetics.Further investigations should focus on elucidating genetic factors influencing treatment responses, identifying additional diagnostic markers, and exploring innovative therapeutic approaches.Collaborative efforts among researchers, clinicians, and policymakers are essential to advance the field, bridge existing knowledge gaps and ultimately enhance the quality of life for individuals living with epilepsy.5| CONCLUSIONIn conclusion, this comprehensive analysis of diverse epilepsy studies underscores the pivotal role of genetic information in tailoring treatments and enhancing patient outcomes.The urgent integration of genetic testing into epilepsy care is imperative.Nevertheless, there is a pressing need for more comprehensive reporting standards within epilepsy research.Our study's limitation includes the inadequacy of databases due to financial constraints, inclusion of different study designs, which may hinder the generalizability of the data.AhilaAli https://orcid.org/0009-0003-1176-7928Simran Ochani https://orcid.org/0000-0002-4125-9575Md.Al Hasibuzzaman https://orcid.org/0000-0003-0548-4836 conducted a clinical trial focused on the CYP1A1 gene to explore its role in predicting drug responses in T A B L E 3 Risk of bias (RoB).
12LE-PP), while also shedding light on the significant total effects of -SH groups in this context.This research offers valuable insights into how specific genetic variants and -SH groups play a role in the management of epilepsy.Mir et al.11presented a case report honing in on the GRIN2A gene and employed gene sequencing as a diagnostic tool.Their treatment strategy involved the use of memantine, although specific treatment outcomes were not detailed.Despite the lack of specific results, this study highlights the potential relevance of the GRIN2A gene in epilepsy cases and emphasizes memantine as a viable treatment option.Andrade12conducted a cohort study centered on the SCN1A gene, employing gene sequencing to identify genetic markers.