Genetic contribution to common epilepsies

Persistence of fish populations to longer, more intense, and more frequent mass mortality events

Over the last decades, mass mortality events have become increasingly common across taxa with sometimes devastating effects on population biomass. In the aquatic environment, fish are sensitive to mass mortality events, particularly at the early life stages that are crucial for population dynamics. However, it has recently been shown for fish, that a single mass mortality event in early life typically does not lead to population collapse. Moreover, the frequency and intensity of extreme events that can cause mass mortality, such as marine heatwaves, are increasing. Here, we show that increasing frequency and intensity of mass mortality events may lead to population collapse. Since the drivers of mass mortality events are diverse, and often linked to climate change, it is challenging to predict the frequency and severity of future mass mortality events. As an alternative, we quantify the probability of population collapse depending on the frequency and intensity as well as the duration of mass mortality events. Based on 39 fish species, we show that the probability of collapse typically increases with increasing frequency, intensity, and duration of the mortality events. In addition, we show that the collapse depends on key traits such as natural mortality, recruitment variation, and density dependence. The presented framework provides quantitative estimates of the sensitivity of fish species to these increasingly common extreme events, which paves the way for potential mitigation actions to alleviate adverse impacts on harvested fish populations across the globe.

Genome-wide identification and phenotypic characterization of seizure-associated copy number variations in 741,075 individuals

Copy number variants (CNV) are established risk factors for neurodevelopmental disorders with seizures or epilepsy. With the hypothesis that seizure disorders share genetic risk factors, we pooled CNV data from 10,590 individuals with seizure disorders, 16,109 individuals with clinically validated epilepsy, and 492,324 population controls and identified 25 genome-wide significant loci, 22 of which are novel for seizure disorders, such as deletions at 1p36.33, 1q44, 2p21-p16.3, 3q29, 8p23.3-p23.2, 9p24.3, 10q26.3, 15q11.2, 15q12-q13.1, 16p12.2, 17q21.31, duplications at 2q13, 9q34.3, 16p13.3, 17q12, 19p13.3, 20q13.33, and reciprocal CNVs at 16p11.2, and 22q11.21. Using genetic data from additional 248,751 individuals with 23 neuropsychiatric phenotypes, we explored the pleiotropy of these 25 loci. Finally, in a subset of individuals with epilepsy and detailed clinical data available, we performed phenome-wide association analyses between individual CNVs and clinical annotations categorized through the Human Phenotype Ontology (HPO). For six CNVs, we identified 19 significant associations with specific HPO terms and generated, for all CNVs, phenotype signatures across 17 clinical categories relevant for epileptologists. This is the most comprehensive investigation of CNVs in epilepsy and related seizure disorders, with potential implications for clinical practice.

The path from scientific discovery to cures for epilepsy

The epilepsies are a complex group of disorders that can be caused by a myriad of genetic and acquired factors. As such, identifying interventions that will prevent development of epilepsy, as well as cure the disorder once established, will require a multifaceted approach. Here we discuss the progress in scientific discovery propelling us towards this goal, including identification of genetic risk factors and big data approaches that integrate clinical and molecular 'omics' datasets to identify common pathophysiological signatures and biomarkers. We discuss the many animal and cellular models of epilepsy, what they have taught us about pathophysiology, and the cutting edge cellular, optogenetic, chemogenetic and anti-seizure drug screening approaches that are being used to find new cures in these models. Finally, we reflect on the work that still needs to be done towards identify at-risk individuals early, targeting and stopping epileptogenesis, and optimizing promising treatment approaches. Ultimately, developing and implementing cures for epilepsy will require a coordinated and immense effort from clinicians and basic scientists, as well as industry, and should always be guided by the needs of individuals affected by epilepsy and their families. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Inter-ictal network of focal epilepsy and effects of clinical factors on network activity

OBJECTIVE

Aim of the study was to explore the inter-ictal, resting-state EEG network in patients with focal epilepsy (FE) and to specify clinical factors that influence network activity.

METHODS

Functional EEG connectivity (EEGfC) differences were computed between 232 FE patients (FE group) and 77 healthy controls. EEGfC was computed among 23 cortical regions within each hemisphere, for 25 very narrow bands from 1 to 25 Hz. We computed independent effects for six clinical factors on EEGfC in the FE group, by ANOVA and post-hoc t-statistics, corrected for multiple comparisons by false discovery rate method.

RESULTS

Robust, statistically significant EEGfC differences emerged between the FE and the healthy control groups. Etiology, seizure type, duration of the illness and antiepileptic treatment were independent factors that influenced EEGfC. Statistically significant results occurred selectively in one or a few very narrow bands and outlined networks. Most abnormal EEGfC findings occurred at frequencies that mediate integrative and motor activities.

CONCLUSIONS

FE patients have abnormal resting-state EEGfC network activity. Clinical factors significantly modify EEGfC.

SIGNIFICANCE

Delineation of the FE network and modifying factors can open the way for targeted investigations and introduction of EEGfC into epilepsy research and practice.

Familial aggregation of focal seizure semiology in the Epilepsy Phenome/Genome Project

OBJECTIVE

To improve phenotype definition in genetic studies of epilepsy, we assessed the familial aggregation of focal seizure types and of specific seizure symptoms within the focal epilepsies in families from the Epilepsy Phenome/Genome Project.

METHODS

We studied 302 individuals with nonacquired focal epilepsy from 149 families. Familial aggregation was assessed by logistic regression analysis of relatives' traits (dependent variable) by probands' traits (independent variable), estimating the odds ratio for each symptom in a relative given presence vs absence of the symptom in the proband.

RESULTS

In families containing multiple individuals with nonacquired focal epilepsy, we found significant evidence for familial aggregation of ictal motor, autonomic, psychic, and aphasic symptoms. Within these categories, ictal whole body posturing, diaphoresis, dyspnea, fear/anxiety, and déjà vu/jamais vu showed significant familial aggregation. Focal seizure type aggregated as well, including complex partial, simple partial, and secondarily generalized tonic-clonic seizures.

CONCLUSION

Our results provide insight into genotype-phenotype correlation in the nonacquired focal epilepsies and a framework for identifying subgroups of patients likely to share susceptibility genes.

Age-associated physiological and pathological changes at the blood-brain barrier: A review

The age-associated decline of the neurological and cognitive functions becomes more and more serious challenge for the developed countries with the increasing number of aged populations. The morphological and biochemical changes in the aging brain are the subjects of many extended research projects worldwide for a long time. However, the crucial role of the blood-brain barrier (BBB) impairment and disruption in the pathological processes in age-associated neurodegenerative disorders received special attention just for a few years. This article gives an overview on the major elements of the blood-brain barrier and its supporting mechanisms and also on their alterations during development, physiological aging process and age-associated neurodegenerative disorders (Alzheimer's disease, multiple sclerosis, Parkinson's disease, pharmacoresistant epilepsy). Besides the morphological alterations of the cellular elements (endothelial cells, astrocytes, pericytes, microglia, neuronal elements) of the BBB and neurovascular unit, the changes of the barrier at molecular level (tight junction proteins, adheres junction proteins, membrane transporters, basal lamina, extracellular matrix) are also summarized. The recognition of new players and initiators of the process of neurodegeneration at the level of the BBB may offer new avenues for novel therapeutic approaches for the treatment of numerous chronic neurodegenerative disorders currently without effective medication.

Synergistic association of STX1A and VAMP2 with cryptogenic epilepsy in North Indian population

INTRODUCTION

"Common epilepsies", merely explored for genetics are the most frequent, nonfamilial, sporadic cases in hospitals. Because of their much debated molecular pathology, there is a need to focus on other neuronal pathways including the existing ion channels.

METHODS

For this study, a total of 214 epilepsy cases of North Indian ethnicity comprising 59.81% generalized, 40.19% focal seizures, and based on epilepsy types, 17.29% idiopathic, 37.38% cryptogenic, and 45.33% symptomatic were enrolled. Additionally, 170 unrelated healthy individuals were also enrolled. Here, we hypothesize the involvement of epilepsy pathophysiology genes, that is, synaptic vesicle cycle, SVC genes (presynapse), ion channels and their functionally related genes (postsynapse). An interactive analysis was initially performed in SVC genes using multifactor dimensionality reduction (MDR). Further, in order to understand the influence of ion channels and their functionally related genes, their interaction analysis with SVC genes was also performed.

RESULTS

A significant interactive two-locus model of STX1A_rs4363087|VAMP2_rs2278637 (presynaptic genes) was observed among SVC variants in all epilepsy cases (P 1000-value = 0.054; CVC = 9/10; OR = 2.86, 95%CI = 1.88-4.35). Further, subgroup analysis revealed stronger interaction for the same model in cryptogenic epilepsy patients only (P 1000-value = 0.012; CVC = 10/10; OR = 4.59, 95%CI = 2.57-8.22). However, interactive analysis of presynaptic and postsynaptic genes did not show any significant association.

CONCLUSIONS

Significant synergistic interaction of SVC genes revealed the possible functional relatedness of presynapse with pathophysiology of cryptogenic epilepsy. Further, to establish the clinical utility of the results, replication in a large and similar phenotypic group of patients is warranted.

Involvement of cortical fast-spiking parvalbumin-positive basket cells in epilepsy

GABAergic interneurons of the parvalbumin-positive fast-spiking basket cells subtype (PV INs) are important regulators of cortical network excitability and of gamma oscillations, involved in signal processing and cognition. Impaired development or function of PV INs has been associated with epilepsy in various animal models of epilepsy, as well as in some genetic forms of epilepsy in humans. In this review, we provide an overview of some of the experimental data linking PV INs dysfunction with epilepsy, focusing on disorders of the specification, migration, maturation, synaptic function, or connectivity of PV INs. Furthermore, we reflect on the potential therapeutic use of cell-type specific stimulation of PV INs within active networks and on the transplantation of PV INs precursors in the treatment of epilepsy and its comorbidities.

Contribution of KCNJ10 gene polymorphisms in childhood epilepsy

The purpose of this study was to investigate the possible association between childhood epilepsy and KCNJ10 gene polymorphisms (rs61822012 and rs2486253). A total of 200 epileptic cases and 200 healthy controls enrolled to this study. Genomic DNAs from the patients and control cases were analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism methods. There were significant associations between the G/T genotype of KCNJ10 gene rs2486253 polymorphism in the idiopathic generalized epilepsy group (P = .037) and in subjects with generalized tonic-clonic seizures (P = .0015). T allele was also increased in patients with generalized tonic-clonic seizures (P = .0158). However, no statistically significant association was found between rs61822012 polymorphism and epilepsy. Our data suggest that G/T genotype of the KCNJ10 gene rs2486253 polymorphism affects risk for development of common types of childhood epilepsy. The T allele of this polymorphism was found to be a seizure-susceptibility allele for tonic-clonic epilepsy.

16p13.11 microdeletion in a patient with hemiconvulsion-hemiplegia-epilepsy syndrome: a case report

We describe a patient with hemiconvulsion-hemiplegia-epilepsy syndrome. The pathophysiology of hemiconvulsion-hemiplegia-epilepsy syndrome remains uncertain and there are probably multiple potential contributing factors. Our patient had a chromosomal 16p13.11 microdeletion that confers susceptibility to various types of epilepsy. This is the first report detailing an association of hemiconvulsion-hemiplegia-epilepsy syndrome with a 16p13.11 deletion and identifies another potential causal factor for hemiconvulsion-hemiplegia-epilepsy syndrome.

6q22.1 microdeletion and susceptibility to pediatric epilepsy

Genomic copy-number variations (CNVs) constitute an important cause of epilepsies and other human neurological disorders. Recent advancement of technologies integrating genome-wide CNV mapping and sequencing is rapidly expanding the molecular field of pediatric neurodevelopmental disorders. In a previous study, a novel epilepsy locus was identified on 6q16.3q22.31 by linkage analysis in a large pedigree. Subsequent array comparative genomic hybridization (array CGH) analysis of four unrelated cases narrowed this region to ∼5 Mb on 6q22.1q22.31. We sought to further narrow the critical region on chromosome 6q22. Array CGH analysis was used in genome-wide screen for CNVs of a large cohort of patients with neurological abnormalities. Long-range PCR and DNA sequencing were applied to precisely map chromosomal deletion breakpoints. Finally, real-time qPCR was used to estimate relative expression in the brain of the candidate genes. We identified six unrelated patients with overlapping microdeletions within 6q22.1q22.31 region, three of whom manifested seizures. Deletions were found to be de novo in 5/6 cases, including all subjects presenting with seizures. We sequenced the deletion breakpoints in four patients and narrowed the critical region to a ∼250-kb segment at 6q22.1 that includes NUS1, several expressed sequence tags (ESTs) that are highly expressed in the brain, and putative regulatory sequences of SLC35F1. Our findings indicate that dosage alteration in particular, of NUS1, EST AI858607, or SLC35F1 are important contributors to the neurodevelopmental phenotype associated with 6q22 deletion, including epilepsy and tremors.

Familial risk of epilepsy: a population-based study

Almost all previous studies of familial risk of epilepsy have had potentially serious methodological limitations. Our goal was to address these limitations and provide more rigorous estimates of familial risk in a population-based study. We used the unique resources of the Rochester Epidemiology Project to identify all 660 Rochester, Minnesota residents born in 1920 or later with incidence of epilepsy from 1935-94 (probands) and their 2439 first-degree relatives who resided in Olmsted County. We assessed incidence of epilepsy in relatives by comprehensive review of the relatives' medical records, and estimated age-specific cumulative incidence and standardized incidence ratios for epilepsy in relatives compared with the general population, according to proband and relative characteristics. Among relatives of all probands, cumulative incidence of epilepsy to age 40 was 4.7%, and risk was increased 3.3-fold (95% confidence interval 2.75-5.99) compared with population incidence. Risk was increased to the greatest extent in relatives of probands with idiopathic generalized epilepsies (standardized incidence ratio 6.0) and epilepsies associated with intellectual or motor disability presumed present from birth, which we denoted 'prenatal/developmental cause' (standardized incidence ratio 4.3). Among relatives of probands with epilepsy without identified cause (including epilepsies classified as 'idiopathic' or 'unknown cause'), risk was significantly increased for epilepsy of prenatal/developmental cause (standardized incidence ratio 4.1). Similarly, among relatives of probands with prenatal/developmental cause, risk was significantly increased for epilepsies without identified cause (standardized incidence ratio 3.8). In relatives of probands with generalized epilepsy, standardized incidence ratios were 8.3 (95% confidence interval 2.93-15.31) for generalized epilepsy and 2.5 (95% confidence interval 0.92-4.00) for focal epilepsy. In relatives of probands with focal epilepsy, standardized incidence ratios were 1.0 (95% confidence interval 0.00-2.19) for generalized epilepsy and 2.6 (95% confidence interval 1.19-4.26) for focal epilepsy. Epilepsy incidence was greater in offspring of female probands than in offspring of male probands, and this maternal effect was restricted to offspring of probands with focal epilepsy. The results suggest that risks for epilepsies of unknown and prenatal/developmental cause may be influenced by shared genetic mechanisms. They also suggest that some of the genetic influences on generalized and focal epilepsies are distinct. However, the similar increase in risk for focal epilepsy among relatives of probands with either generalized (2.5-fold) or focal epilepsy (2.6-fold) may reflect some coexisting shared genetic influences.

A common susceptibility factor of both autism and epilepsy: functional deficiency of GABA A receptors

Autism and epilepsy are common childhood neurological disorders with a great heterogeneity of clinical phenotypes as well as risk factors. There is a high co-morbidity of autism and epilepsy. The neuropathology of autism and epilepsy has similar histology implicating the processes of neurogenesis, neural migration, programmed cell death, and neurite outgrowth. Genetic advances have identified multiple molecules that participate in neural development, brain network connectivity, and synaptic function which are involved in the pathogenesis of autism and epilepsy. Mutations in GABA(A) receptor subunit have been frequently associated with epilepsy, autism, and other neuropsychiatric disorders. In this paper, we address the hypothesis that functional deficiency of GABAergic signaling is a potential common molecular mechanism underpinning the co-morbidity of autism and epilepsy.

Distribution of disease-associated copy number variants across distinct disorders of cognitive development

OBJECTIVE

The purpose of the present study was to discover the extent to which distinct DSM disorders share large, highly recurrent copy number variants (CNVs) as susceptibility factors. We also sought to identify gene mechanisms common to groups of diagnoses and/or specific to a given diagnosis based on associations with CNVs.

METHOD

Systematic review of 820 PubMed articles on autism spectrum disorder (ASD), intellectual disability (ID), schizophrenia, and epilepsy produced 54 CNVs associated with one or several disorders. Pathway analysis on genes implicated by CNVs in different groupings was conducted.

RESULTS

The majority of CNVs were found in ID with the other disorders somewhat subsumed, yet certain CNVs were associated with isolated or groups of disorders. Based on genes implicated by CNVs, ID encompassed 96.8% of genes in ASD, 92.8% of genes in schizophrenia, and 100.0% of genes in epilepsy. Pathway analysis revealed that synapse processes were enriched in ASD, ID, and schizophrenia. Disease-specific processes were identified in ID (actin cytoskeleton processes), schizophrenia (ubiquitin-related processes), and ASD (synaptic vesicle transport and exocytosis).

CONCLUSIONS

Intellectual disability may arise from the broadest range of genetic pathways, and specific subsets of these pathways appear to be relevant to other disorders or combinations of these disorders. It is clear that statistically significant CNVs across disorders of cognitive development are highly enriched for biological processes related to the synapse. There are also disorder-specific processes that may aid in understanding the distinct presentations and pathophysiology of these disorders.

Epilepsy treatment: a paradigm shift is urgently need

Epilepsy affects between 5 and 10 people in a 1,000 and carries considerable morbidity and premature mortality. The complex inheritance pattern of a lowered seizure threshold is not fully understood but is likely to be polygenic. In the majority of people with epilepsy, we do not understand the pathophysiology, how a seizure is triggered, and how it can be prevented. In the centennial year of the discovery of the antiepileptic properties of phenobarbital, we have over 20 antiepileptic drugs; however, none have dramatically changed the long-term prognosis of the condition. The cascade of events triggering epilepsy is likely to vary greatly among individuals. The hope for the future is a shift of paradigm away from the symptomatic approach that currently exists. Indeed, once epileptogenesis is fully understood, treatment can be targeted at specific mechanisms, and then we will have truly disease-modifying therapies.

Epilepsy with cognitive deficit and autism spectrum disorders: prospective diagnosis by array CGH

The clinical significance of chromosomal microdeletions and microduplications was predicted based on their gene content, de novo or familial inheritance and accumulated knowledge recorded on public databases. A patient group comprised of 247 cases with epilepsy and its common co-morbidities of developmental delay, intellectual disability, autism spectrum disorders, and congenital abnormalities was reviewed prospectively in a diagnostic setting using a standardized oligo-array CGH platform. Seventy-three (29.6%) had copy number variations (CNVs) and of these 73 cases, 27 (37.0%) had CNVs that were likely causative. These 27 cases comprised 10.9% of the 247 cases reviewed. The range of pathogenic CNVs associated with seizures was consistent with the existence of many genetic determinants for epilepsy.

Ion channels in genetic and acquired forms of epilepsy

Genetic mutations causing dysfunction of both voltage- and ligand-gated ion channels make a major contribution to the cause of many different types of familial epilepsy. Key mechanisms comprise defective Na(+) channels of inhibitory neurons, or GABA(A) receptors affecting pre- or postsynaptic GABAergic inhibition, or a dysfunction of different types of channels at axon initial segments. Many of these ion channel mutations have been modelled in mice, which has largely contributed to the understanding of where and how the ion channel defects lead to neuronal hyperexcitability. Animal models of febrile seizures or mesial temporal epilepsy have shown that dendritic K(+) channels, hyperpolarization-activated cation channels and T-type Ca(2+) channels play important roles in the generation of seizures. For the latter, it has been shown that suppression of their function by pharmacological mechanisms or in knock-out mice can antagonize epileptogenesis. Defects of ion channel function are also associated with forms of acquired epilepsy. Autoantibodies directed against ion channels or associated proteins, such as K(+) channels, LGI1 or NMDA receptors, have been identified in epileptic disorders that can largely be included under the term limbic encephalitis which includes limbic seizures, status epilepticus and psychiatric symptoms. We conclude that ion channels and associated proteins are important players in different types of genetic and acquired epilepsies. Nevertheless, the molecular bases for most common forms of epilepsy are not yet clear, and evidence to be discussed indicates just how much more we need to understand about the complex mechanisms that underlie epileptogenesis.

Application of array comparative genomic hybridization in 102 patients with epilepsy and additional neurodevelopmental disorders

Copy-number variants (CNVs) collectively represent an important cause of neurodevelopmental disorders such as developmental delay (DD)/intellectual disability (ID), autism, and epilepsy. In contrast to DD/ID, for which the application of microarray techniques enables detection of pathogenic CNVs in -10-20% of patients, there are only few studies of the role of CNVs in epilepsy and genetic etiology in the vast majority of cases remains unknown. We have applied whole-genome exon-targeted oligonucleotide array comparative genomic hybridization (array CGH) to a cohort of 102 patients with various types of epilepsy with or without additional neurodevelopmental abnormalities. Chromosomal microarray analysis revealed 24 non-polymorphic CNVs in 23 patients, among which 10 CNVs are known to be clinically relevant. Two rare deletions in 2q24.1q24.3, including KCNJ3 and 9q21.13 are novel pathogenic genetic loci and 12 CNVs are of unknown clinical significance. Our results further support the notion that rare CNVs can cause different types of epilepsy, emphasize the efficiency of detecting novel candidate genes by whole-genome array CGH, and suggest that the clinical application of array CGH should be extended to patients with unexplained epilepsies.

Atypical face shape and genomic structural variants in epilepsy

Many pathogenic structural variants of the human genome are known to cause facial dysmorphism. During the past decade, pathogenic structural variants have also been found to be an important class of genetic risk factor for epilepsy. In other fields, face shape has been assessed objectively using 3D stereophotogrammetry and dense surface models. We hypothesized that computer-based analysis of 3D face images would detect subtle facial abnormality in people with epilepsy who carry pathogenic structural variants as determined by chromosome microarray. In 118 children and adults attending three European epilepsy clinics, we used an objective measure called Face Shape Difference to show that those with pathogenic structural variants have a significantly more atypical face shape than those without such variants. This is true when analysing the whole face, or the periorbital region or the perinasal region alone. We then tested the predictive accuracy of our measure in a second group of 63 patients. Using a minimum threshold to detect face shape abnormalities with pathogenic structural variants, we found high sensitivity (4/5, 80% for whole face; 3/5, 60% for periorbital and perinasal regions) and specificity (45/58, 78% for whole face and perinasal regions; 40/58, 69% for periorbital region). We show that the results do not seem to be affected by facial injury, facial expression, intellectual disability, drug history or demographic differences. Finally, we use bioinformatics tools to explore relationships between facial shape and gene expression within the developing forebrain. Stereophotogrammetry and dense surface models are powerful, objective, non-contact methods of detecting relevant face shape abnormalities. We demonstrate that they are useful in identifying atypical face shape in adults or children with structural variants, and they may give insights into the molecular genetics of facial development.

Advances in epilepsy genetics and genomics

Current and emerging technologies for mutation identification are changing the landscape of genetics and accelerating the pace of discovery. Application of high throughput genomic analysis to epilepsy will advance our understanding of the genetic contribution to common forms of epilepsy and suggest novel therapeutic strategies for improved treatment.

Epi4K: gene discovery in 4,000 genomes

A major challenge in epilepsy research is to unravel the complex genetic mechanisms underlying both common and rare forms of epilepsy, as well as the genetic determinants of response to treatment. To accelerate progress in this area, the National Institute of Neurological Disorders and Stroke (NINDS) recently offered funding for the creation of a “Center without Walls” to focus on the genetics of human epilepsy. This article describes Epi4K, the collaborative study supported through this grant mechanism and having the aim of analyzing the genomes of a minimum 4,000 subjects with highly selected and well-characterized epilepsy.

Opportunities and challenges for genome sequencing in the clinic

Human genome sequencing technology is developing rapidly. These developments are providing exciting opportunities for genetic mapping of human traits, ranging from accelerated discovery of mutations underlying relatively simple Mendelian disorders to more genetically complex human diseases. This chapter outlines the development of whole-genome sequencing in a historical context of genetic mapping and explores the impact that sequencing is having on gene discovery study design. Using the example of epilepsy, the authors outline the opportunities and barriers for the translation of genetic predictors from discovery to the clinic. Finally, the authors discuss the practical challenges of actual implementation of whole-genome sequencing to the clinic.

Interview: The National Institute of Neurological Diseases and Stroke/American Epilepsy Society benchmarks and research priorities for epilepsy research

Daniel H Lowenstein, MD, is the Robert B and Ellinor Aird Professor and Vice-Chairman of Neurology, Director of the Epilepsy Center, and Director of Physician–Scientist Education and Training at the University of California, San Francisco (UCSF). He received his BA in Mathematics from the University of Colorado and MD from Harvard Medical School. He completed his neurology residency training at UCSF. Dr Lowenstein is a clinician–scientist who has studied both basic science and clinical aspects of epilepsy. In recent years, he has been an organizer of a large-scale, international effort to study the complex genetics of epilepsy, known as the Epilepsy Phenome/Genome Project. He has been actively involved in advancing the cause of epilepsy at the national and international level. Dr Lowenstein served as President of the American Epilepsy Society from 2003 to 2004 and the National Institute of Neurological Diseases and Stroke (NINDS) Advisory Council from 2000 to 2004, and has overseen the development of the NINDS Epilepsy Research Benchmarks since their inception in 2000.

Pharmacogenomics and epilepsy: the road ahead

Epilepsy is one of the most common, serious neurological disorders, affecting an estimated 50 million people worldwide. The condition is typically treated using antiepileptic drugs of which there are 16 in widespread use. However, there are many different syndrome and seizure types within epilepsy and information guiding clinicians on the most effective drug and dose for individual patients is lacking. Further, all of the antiepileptic drugs have associated adverse reactions, some of which are severe and life-threatening. Here, we review the pharmacogenomic work to date in the context of these issues and comment on key aspects of study design that are required to speed up the identification of clinically relevant genetic factors.

Genomic microdeletions associated with epilepsy: not a contraindication to resective surgery

PURPOSE

Several recent reports of genomic microdeletions in epilepsy will generate further research; discovery of more microdeletions and other important classes of variants may follow. Detection of such genetic abnormalities in patients being evaluated for surgical treatment might raise concern that a genetic defect, possibly widely expressed in the brain, will affect surgical outcome.

METHODS

A reevaluation was undertaken of clinical presurgical data, histopathology of surgical specimen, and postsurgical outcome in patients with mesial temporal lobe epilepsy (MTLE) who have had surgical treatment for their drug-resistant seizures, and who have been found to have particular genomic microdeletions.

KEY FINDINGS

Three thousand eight hundred twelve patients with epilepsy were genotyped and had a genome-wide screen to identify copy number variation. Ten patients with MTLE, who had resective epilepsy surgery, were found to have 16p13.11 microdeletions or other microdeletions >1 Mb. On histopathology, eight had classical hippocampal sclerosis (HS), one had nonspecific findings, and one had a hamartoma. Median postsurgical follow-up time was 48 months (range 10-156 months). All patients with HS were seizure-free after surgery, International League Against Epilepsy (ILAE) outcome class 1, at last follow-up; the patient with nonspecific pathology had recurrence of infrequent seizures after 7 years of seizure freedom. The patient with a hamartoma never became seizure-free.

SIGNIFICANCE

  Large microdeletions can be found in patients with "typical" MTLE. In this small series, patients with MTLE who meet criteria for resective surgery and harbor large microdeletions, at least those we have detected, can have a good postsurgical outcome. Our findings add to the spectrum of causal heterogeneity of MTLE + HS.