A case of SUDEP in a patient with Dravet syndrome with SCN1A mutation

Antiseizure medication and SUDEP - a need for unifying methodology in research

The risk of sudden unexpected death in epilepsy (SUDEP) increases with the frequency of generalized tonic-clonic seizures. Carbamazepine (CBZ) and lamotrigine (LTG) have been suggested to increase the risk. However, the prevailing viewpoint is that the choice of antiseizure medication (ASM) does not influence the occurrence. We have explored the approach to addressing this question in relevant studies to evaluate the validity of the conclusions reached. A systematic search was performed in PubMed to identify all controlled studies on SUDEP risk in individuals on CBZ or LTG. Studies were categorized according to whether idiopathic generalized epilepsy (IGE) or females were considered separately, and whether data were adjusted for seizure frequency. Eight studies on CBZ and six studies on LTG were identified. For CBZ, one study showed a significantly increased risk of SUDEP without adjustment for seizure frequency. Another study found significantly increased risk after statistical adjustment for seizure frequency and one study found increased risk with high blood levels. Five other studies found no increase in risk. For LTG, one study showed a significantly increased risk in patients with IGE as opposed to focal epilepsy, and another study showed a significantly increased risk in females. None of the subsequent studies on LTG and none of the studies on CBZ considered females with IGE separately. Taken together the available studies suggest that LTG, and possibly CBZ, may increase occurrence of SUDEP when used in females with IGE. Additional studies with sub-group analysis of females with IGE are needed.

Inherited SCN1A missense mutation in a Dravet Syndrome family: Neuropathological correlation, family screening and implications for adult carriers

INTRODUCTION

Neuropathological findings in Dravet Syndrome (DS) are scarce, especially in adult patients, and often do not have a genetic confirmation. Additionally, the missense SCN1A pathogenic variant found has only been described as de novo mutation in previous literature.

METHODS

We describe the clinical and genetic findings of a family (including three sisters and his father), using Sanger sequencing in the three sisters and in postmortem brain tissue in the father. The present study also shows the neuropathological findings of the father.

RESULTS

Despite the presence of long term drug resistant epilepsy, starting with febrile seizures between 6 and 12 months of age, and intellectual disability (ID), the three sisters were diagnosed with DS in adulthood, identifying a missense SCN1A pathogenic variant in exon 20, previously described as de novo -p.Gly1332Glu (c .3995 G>A). The oldest sister had the most severe phenotype, with severe ID and wheel chair dependency, passing away at 52. The other two sisters had a moderate phenotype, being at the present seizure free, but with significant comorbidities, such as crouch gait and parkinsonism. Several relatives from the paternal path (including the father) presented epilepsy, but without ID. The father was diagnosed with Alzheimer´s Disease (AD) at 60, and because he donated his brain, the same variant was confirmed in postmortem study. Neither the MRI nor the histopathology showed specific morphological changes for DS, consistent with previous studies.

CONCLUSIONS

This work supports the need to review the clinical and genetic spectra of DS in adults with epilepsy and unknown ID. The clinical consequences of this syndrome seem to have a functional rather than a structural basis, supported by the absence of specific neuropathological findings.

Sudden Infant Death Syndrome: Risk Factors and Newer Risk Reduction Strategies

Sudden infant death syndrome (SIDS) continues to be one of the top causes of infant death in the U.S. Despite significant public health initiatives focused on high-risk populations to enhance sleep environments and techniques. The SIDS rate has remained stable in recent years. Risk factors and newer risk reduction strategies for SIDS are the focus of this review article. We conducted a comprehensive literature search on Medline, Cochrane, Embase, and Google Scholar until July 2022. The following search strings and Medical Subject Heading (MeSH) terms were used: "SIDS," "Sudden Infant Death" and "SUID". We explored the literature on SIDS for its epidemiology, pathophysiology, the role of various etiologies and their influence, associated complications leading to SIDS, and preventive and treatment modalities. Despite a more than 50% drop-in rates since the start of the "Back to Sleep" campaign in 1994, sudden infant death syndrome (SIDS) continues to be the top cause of post-neonatal mortality in the United States, despite continued educational initiatives that support safe sleep and other risk reduction strategies. The new American Academy of Pediatrics guidelines for lowering the risk of SIDS include a lot of emphasis on sleeping habits, bedding, and environment but also include elements that are frequently ignored (i.e., prenatal care, smoking, alcohol and drug use, and childhood vaccinations). This study highlights these less-frequently discussed aspects and identifies treatments that have produced beneficial behavioral shifts that benefit newborns as well as their mothers' health and wellbeing.

Copy Number Variation and Structural Genomic Findings in 116 Cases of Sudden Unexplained Death between 1 and 28 Months of Age

In sudden unexplained death in pediatrics (SUDP) the cause of death is unknown despite an autopsy and investigation. The role of copy number variations (CNVs) in SUDP has not been well-studied. Chromosomal microarray (CMA) data are generated for 116 SUDP cases with age at death between 1 and 28 months. CNVs are classified using the American College of Medical Genetics and Genomics guidelines and CNVs in our cohort are compared to an autism spectrum disorder (ASD) cohort, and to a control cohort. Pathogenic CNVs are identified in 5 of 116 cases (4.3%). Variants of uncertain significance (VUS) favoring pathogenic CNVs are identified in 9 cases (7.8%). Several CNVs are associated with neurodevelopmental phenotypes including seizures, ASD, developmental delay, and schizophrenia. The structural variant 47,XXY is identified in two cases (2/69 boys, 2.9%) not previously diagnosed with Klinefelter syndrome. Pathogenicity scores for deletions are significantly elevated in the SUDP cohort versus controls (p = 0.007) and are not significantly different from the ASD cohort. The finding of pathogenic or VUS favoring pathogenic CNVs, or structural variants, in 12.1% of cases, combined with the observation of higher pathogenicity scores for deletions in SUDP versus controls, suggests that CMA should be included in the genetic evaluation of SUDP.

Sudden Unexpected Death in Epilepsy

Epilepsy is a complex neurological condition with numerous etiologies and treatment options. In a subset of these patients, sudden unexpected death can occur, and to date, there are numerous explanations as to the pathophysiological mechanisms and how to mitigate these catastrophic outcomes. Approximately 2.3 million Americans have epilepsy, and nearly 150,000 people develop the condition each year. Sudden unexpected death in epilepsy (SUDEP) accounts for 2–18% of all epilepsy-related deaths and this is equivalent to one death in 1000 person-years of diagnosed epilepsy. It is more common in young adults aged 20–45. Seizures in the past year; the absence of terminal remission in the last five years; increased seizure frequency, particularly GTCS; and nocturnal seizures are the most potent modifiable risk factors for SUDEP. Patients not receiving any antiepileptic drug therapy are at higher risk of SUDEP. Patient education on medication compliance; care plans for seizure clusters (rescue medicines); epilepsy self-management programs; and lifestyle changes to avoid seizure-triggering factors, including avoiding excessive alcohol use and sleep deprivation, should be provided by health care providers. Continued research into SUDEP will hopefully lead to effective interventions to minimize occurrences. At present, aggressive control of epilepsy and enhanced education for individuals and the public are the most effective weapons for combating SUDEP. This narrative review focuses on updated information related to SUDEP epidemiology; pathophysiology; risk factor treatment options; and finally, a discussion of important clinical studies. We seek to encourage clinicians who care for patients with epilepsy to be aggressive in controlling seizure activity and diligent in their review of risk factors and education of patients and their families about SUDEP.

SCN1A-Related Epilepsy: Novel Mutations and Rare Phenotypes

Objectives

To expand the genotypes and phenotypes of sodium voltage-gated channel alpha subunit 1 (SCN1A)-related epilepsy.

Methods

We retrospectively collected the clinical and genetic information of 22 epilepsy patients (10 males, 12 females; mean: 9.2 ± 3.9 years; 3.9–20.3 years) carrying 22 variants of SCN1A. SCN1A mutations were identified by next-generation sequencing.

Results

Twenty-two variants were identified, among which 12 have not yet been reported. The median age at seizure onset was 6 months. Sixteen patients were diagnosed with Dravet syndrome (DS), two with genetic epilepsy with febrile seizures plus [one evolved into benign epilepsy with centrotemporal spikes (BECTS)], one with focal epilepsy, one with atypical childhood epilepsy with centrotemporal spikes (ABECTS) and two with unclassified epilepsy. Fourteen patients showed a global developmental delay/intellectual disability (GDD/ID). Slow background activities were observed in one patient and epileptiform discharges were observed in 11 patients during the interictal phase.

Significance

This study enriches the genotypes and phenotypes of SCN1A-related epilepsy. The clinical characteristics of patients with 12 previously unreported variants were described.

Extending the Phenotype Related to SCN1A Gene: Arthrogryposis, Movement Disorders, and Malformations of Cortical Development

BACKGROUND

Expand the knowledge about the clinical phenotypes associated with pathogenic or likely pathogenic variants in the SCN1A gene.

METHODS

The study was carried out in 15 patients with SCN1A variants. The complete phenotype of the patients was evaluated. A systematic search was carried out in the scientific literature for those unexpected symptoms.

RESULTS

Ten patients showed a missense variant, whereas the remaining showed different loss-of-function variants. Twelve (80%) had Dravet syndrome. Two (13.3%) had Epilepsy with febrile seizures plus. Three (20%) presented an atypical phenotype. One of them was developmental and epileptic encephalopathy with arthrogryposis, the other Dravet syndrome and movement disorder, and lastly one patient had Dravet syndrome and malformations of the cortical development.

CONCLUSION

The exhaustive assessment of patients with pathogenic alterations detected in massive sequencing can help us to expand the phenotype, understand the etiopathogenesis associated with each genetic abnormality, and thus improve the prognosis and management of future patients.

Sudden death in epilepsy: There is room for intracranial pressure

INTRODUCTION

Sudden unexpected death in patients with epilepsy (SUDEP) remains a poorly understood entity, and it is unclear whether the same pathomechanisms underlie all sudden deaths occurring in patients with epilepsy. One aspect not included in current models of SUDEP is the role of increased intracranial pressure (ICP) which can be observed immediately upon seizure activity in neurosurgical practice.

METHODS

We conducted a systematic review of the occurrence of edema in patients with epilepsy reported to have died of sudden death who underwent brain autopsy or postmortem brain imaging and discuss how increased ICP may contribute to clinical features of SUDEP.

RESULTS

19 eligible studies comprising a total of 623 patients were identified. Edema-mostly mild or moderate-was reported in 17% of cases and 74% of studies. 1% (n = 6) of the overall cases were clearly identified as having Dravet syndrome or an SCN1A mutation. In these patients, edema was found in 4 (67%) of cases.

CONCLUSION

Edema is regularly found in patients with epilepsy classified to have died from SUDEP. We argue that seizures preceding SUDEP may in certain cases elicit acute edema which may represent an additional contributing factor in the cascade of events leading to sudden death of patients with epilepsy. Furthermore, we hypothesize that mild edema may especially progress to severe edema in patients with sodium channel mutations which may represent an important mechanism to investigate in the context of understanding the significantly elevated risk of SUDEP in patients with SCN1A mutations.

The role of sodium channels in sudden unexpected death in pediatrics

BACKGROUND

Sudden Unexpected Death in Pediatrics (SUDP) is a tragic event, likely caused by the complex interaction of multiple factors. The presence of hippocampal abnormalities in many children with SUDP suggests that epilepsy-related mechanisms may contribute to death, similar to Sudden Unexplained Death in Epilepsy. Because of known associations between the genes SCN1A and SCN5A and sudden death, and shared mechanisms and patterns of expression in genes encoding many voltage-gated sodium channels (VGSCs), we hypothesized that individuals dying from SUDP have pathogenic variants across the entire family of cardiac arrhythmia- and epilepsy-associated VGSC genes.

METHODS

To address this hypothesis, we evaluated whole-exome sequencing data from infants and children with SUDP for variants in VGSC genes, reviewed the literature for all SUDP-associated variants in VGSCs, applied a novel paralog analysis to all variants, and evaluated all variants according to American College of Medical Genetics and Genomics (ACMG) guidelines.

RESULTS

In our cohort of 73 cases of SUDP, we assessed 11 variants as pathogenic in SCN1A, SCN1B, and SCN10A, genes with long-standing disease associations, and in SCN3A, SCN4A, and SCN9A, VGSC gene paralogs with more recent disease associations. From the literature, we identified 82 VGSC variants in SUDP cases. Pathogenic variants clustered at conserved amino acid sites intolerant to variation across the VGSC genes, which is unlikely to occur in the general population (p < .0001). For 54% of variants previously reported in literature, we identified conflicting evidence regarding pathogenicity when applying ACMG criteria and modern population data.

CONCLUSION

We report variants in several VGSC genes in cases with SUDP, involving both arrhythmia- and epilepsy-associated genes. Accurate variant assessment as well as future studies are essential for an improved understanding of the contribution of sodium channel-related variants to SUDP.

Alterations of the Hippocampal Neurogenic Niche in a Mouse Model of Dravet Syndrome

Hippocampal neurogenesis, the process by which neural stem cells (NSCs) continuously generate new neurons in the dentate gyrus (DG) of most mammals including humans, is chiefly regulated by neuronal activity. Thus, severe alterations have been found in samples from epilepsy patients and in the hippocampal neurogenic niche in mouse models of epilepsy. Reactive-like and gliogenic NSCs plus aberrant newborn neurons with altered migration, morphology, and functional properties are induced by seizures in experimental models of temporal lobe epilepsy. Hippocampal neurogenesis participates in memory and learning and in the control of anxiety and stress. It has been therefore hypothesized that part of the cognitive symptoms associated with epilepsy could be promoted by impaired hippocampal neurogenesis. We here analyze for the first time the alterations of the neurogenic niche in a novel mouse model of Dravet syndrome (DS), a genetic encephalopathy with severe epilepsy in infancy and multiple neurological comorbidities. Scn1a^WT/A1783V mice, hereafter referred to as DS, carrying a heterozygous and clinically relevant SCN1A mutation (A1783V) recapitulate the disease at the genetic and phenotypic levels. We demonstrate that in the neurogenic niche of young adult DS mice there are fewer NSCs, they have impaired cell division and bear reactive-like morphology. In addition, there is significant aberrant neurogenesis. Newborn immature neurons migrate abnormally, and several morphological features are drastically changed. Thus, this study shows for the first time important modifications in hippocampal neurogenesis in DS and opens venues for further research on this topic.

Defective Excitatory/Inhibitory Synaptic Balance and Increased Neuron Apoptosis in a Zebrafish Model of Dravet Syndrome

Dravet syndrome is a type of severe childhood epilepsy that responds poorly to current anti-epileptic drugs. In recent years, zebrafish disease models with Scn1Lab sodium channel deficiency have been generated to seek novel anti-epileptic drug candidates, some of which are currently undergoing clinical trials. However, the spectrum of neuronal deficits observed following Scn1Lab depletion in zebrafish larvae has not yet been fully explored. To fill this gap and gain a better understanding of the mechanisms underlying neuron hyperexcitation in Scn1Lab-depleted larvae, we analyzed neuron activity in vivo using combined local field potential recording and transient calcium uptake imaging, studied the distribution of excitatory and inhibitory synapses and neurons as well as investigated neuron apoptosis. We found that Scn1Lab-depleted larvae displayed recurrent epileptiform seizure events, associating massive synchronous calcium uptakes and ictal-like local field potential bursts. Scn1Lab-depletion also caused a dramatic shift in the neuronal and synaptic balance toward excitation and increased neuronal death. Our results thus provide in vivo evidence suggesting that Scn1Lab loss of function causes neuron hyperexcitation as the result of disturbed synaptic balance and increased neuronal apoptosis.

Perception of impact of Dravet syndrome on children and caregivers in multiple countries: looking beyond seizures

AIM

To assess the relevance and generalizability across countries of concepts of the impact of Dravet syndrome beyond seizures, as recognized by families.

METHOD

Caregivers of children with Dravet syndrome in four countries (Australia [n=8]; USA, UK, and Italy [all n=4]) participated in 1-hour qualitative telephone interviews, identifying key Dravet syndrome concepts. Interviews were recorded, transcribed, and, where necessary, translated into English for thematic analysis. Conceptual saturation was assessed and findings compared to the previously developed French conceptual disease model.

RESULTS

The most common seizure types reported by caregivers were tonic-clonic, absence, or focal-impaired awareness (localized/partial). Fever and physical activity were the most commonly reported triggers. Patient-relevant impacts included impairment in cognition, motor skills, communication, social skills, and behavioural functioning. Caregivers consistently reported negative social, physical, and family impacts. Concepts identified in the interviews showed similarity with the French conceptual model. Minor differences between countries are likely to reflect variations in health care systems.

INTERPRETATION

Findings in Italy, Australia, UK, and USA confirm that the key impacts of Dravet syndrome on children and caregivers identified in France are generalizable across countries. Key symptom and impact concepts relevant to children and parents should be targeted as critical outcomes in new therapy evaluations.

WHAT THIS PAPER ADDS

Relevance of the impact of Dravet syndrome on children and caregivers was confirmed across countries. Patient and caregiver-relevant Dravet syndrome impacts contribute to poorer health-related quality of life. Indirect seizure impacts were reported to be as important as direct impacts. Country-specific differences in concepts probably reflect differences in health care systems.

Functional Nutrients for Epilepsy

Epilepsy is a common neurological disorder of which seizures are a core symptom. Approximately one third of epileptic patients are resistant to antiepileptic drugs and therefore require alternative therapeutic options. Dietary and nutritional supplements can in some cases replace drugs, but with the exception of ketogenic diets, there are no officially recommended dietary considerations for patients with epilepsy. In this review we summarize a selection of nutritional suggestions that have proved beneficial in treating different types of epilepsy. We describe the types of seizures and epilepsy and follow this with an introduction to basic molecular mechanisms. We then examine several functional nutrients for which there is clinical evidence of therapeutic efficacy in reducing seizures or epilepsy-associated sudden death. We also discuss experimental results that demonstrate possible molecular mechanisms elicited by the administration of various nutrients. The availability of multiple dietary and nutritional candidates that show favorable outcomes in animals implies that assessing the clinical potential of these substances will improve translational medicine, ultimately benefitting epilepsy patients.

A systematic review of sudden unexpected death in epilepsy (SUDEP) in childhood

BACKGROUND

Sudden Unexpected Death in Epilepsy (SUDEP) is a significant cause of death in childhood epilepsy, and causes considerable concern to patients and their families. Despite this, the condition remains poorly understood. This systematic review investigates the risk factors, pathophysiology, and circumstances associated with childhood SUDEP. It aimed to explore the etiology of SUDEP and inform clinicians approaching SUDEP risk disclosure.

METHODS

A structured electronic database search of MEDLINE, CENTRAL, EMBASE, and ISI web of science was conducted. Studies were included if they described clinical details of one or more patients, aged 18 years of age and below, who had SUDEP. Two reviewers independently reviewed each article for data extraction and quality assessment.

RESULTS

Information on 108 cases of pediatric SUDEP was extracted from 22 included studies. These comprised five cohort studies, four retrospective case control studies, seven case series, and five case reports. Factors that appeared to be linked to pediatric SUDEP included those associated with severe epilepsy (early age of onset, high seizure frequency, intellectual impairment and developmental delay, multiple antiepileptic drug therapy, and structural abnormalities). The majority of included studies was noncomparative and had significant risk of bias.

CONCLUSIONS

There is currently insufficient evidence to determine the etiology of pediatric SUDEP. Current best practice to prevent pediatric SUDEP is to optimize the management of epilepsy. A national SUDEP registry would provide invaluable high-quality data and insights into modifiable risk factors, genetic predispositions, and novel prevention strategies.

Cardiac arrhythmia and neuroexcitability gene variants in resected brain tissue from patients with sudden unexpected death in epilepsy (SUDEP)

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality in young adults. The exact mechanisms are unknown but death often follows a generalized tonic–clonic seizure. Proposed mechanisms include seizure-related respiratory, cardiac, autonomic, and arousal dysfunction. Genetic drivers underlying SUDEP risk are largely unknown. To identify potential SUDEP risk genes, we compared whole-exome sequences (WES) derived from formalin-fixed paraffin embedded surgical brain specimens of eight epilepsy patients who died from SUDEP with seven living controls matched for age at surgery, sex, year of surgery and lobe of resection. We compared identified variants from both groups filtering known polymorphisms from publicly available data as well as scanned for epilepsy and candidate SUDEP genes. In the SUDEP cohort, we identified mutually exclusive variants in genes involved in µ-opiod signaling, gamma-aminobutyric acid (GABA) and glutamate-mediated synaptic signaling, including ARRB2, ITPR1, GABRR2, SSTR5, GRIK1, CTNAP2, GRM8, GNAI2 and GRIK5. In SUDEP patients we also identified variants in genes associated with cardiac arrhythmia, including KCNMB1, KCNIP1, DPP6, JUP, F2, and TUBA3D, which were not present in living epilepsy controls. Our data shows that genomic analysis of brain tissue resected for seizure control can identify potential genetic biomarkers of SUDEP risk.

Gene variants associated with abnormal heart rhythm and neuronal excitability may increase the risk of Sudden Unexpected Death in Epilepsy (SUDEP). SUDEP is the most common cause of death directly related to epilepsy, but little is known about the risk factors and mechanisms through which seizures can lead to death. Daniel Friedman, Orrin Devinsky and colleagues at New York University Langone Medical Center, US, compared whole-exome sequences from brain tissue belonging to eight epilepsy patients who died from SUDEP and seven matched living controls who had brain tissue removed for epilepsy treatment. In the SUDEP cases they identified 13 rare gene variants involved in cardiac arrhythmia and excitatory neurotransmission as potential genetic biomarkers of SUDEP risk. Further understanding the genetic contribution to epilepsy-related mortality will help develop effective preventive strategies.

Sudden unexpected death in epilepsy

People with epilepsy have increased risk of premature death, and their life expectancy may reduce by 2-10 yr. Population- and hospital-based studies have shown that the excess mortality in epilepsy is not entirely explained by deaths directly attributable to epilepsy such as accidents and drowning during a seizure. It is also significantly contributed by deaths from other causes such as cardiac deaths, deaths due to malignancies and other causes. It had recently been recognized that sudden unexpected deaths in epilepsy (SUDEP) contributed to a small yet important proportion of mortality in epilepsy. SUDEPs are deaths (witnessed or unwitnessed) unrelated to trauma, drowning or status epilepticus and not attributable to any specific medical conditions. Several factors related to epilepsy and drug therapy have been found to be associated with higher risk of SUDEP.

The role of antiepileptic drugs in sudden unexpected death in epilepsy

Sudden unexpected death in epilepsy (SUDEP) primarily affects young adults and is the leading cause of death related directly to seizures. High frequency of generalized tonic-clonic seizures is the most important risk factor, and effective seizure protection is probably the most important measure to prevent these tragic deaths. For several years a potential role of antiepileptic drugs (AEDs) has been discussed, but at present there is wide agreement that choice of AED therapy does not influence the risk. However, although it is well known that the efficacy and safety profiles of AEDs may differ significantly when used in the treatment of genetic epilepsy compared to symptomatic or cryptogenic epilepsy, this has generally been overlooked in epidemiologic studies of possible relationships between AEDs and SUDEP. Consequently important information about drug safety may have been lost. This review challenges the current view that no AED can increase the risk of SUDEP.

Clinical and histopathological outcomes in patients with SCN1A mutations undergoing surgery for epilepsy

OBJECT

Mutations in the sodium channel alpha 1 subunit gene (SCN1A) have been associated with a wide range of epilepsy phenotypes including Dravet syndrome. There currently exist few histopathological and surgical outcome reports in patients with this disease. In this case series, the authors describe the clinical features, surgical pathology, and outcomes in 6 patients with SCN1A mutations and refractory epilepsy who underwent focal cortical resection prior to uncovering the genetic basis of their epilepsy.

METHODS

Medical records of SCN1A mutation-positive children with treatment-resistant epilepsy who had undergone resective epilepsy surgery were reviewed retrospectively. Surgical pathology specimens were reviewed.

RESULTS

All 6 patients identified carried diagnoses of intractable epilepsy with mixed seizure types. Age at surgery ranged from 18 months to 20 years. Seizures were refractory to surgery in every case. Surgical histopathology showed evidence of subtle cortical dysplasia in 4 of 6 patients, with more neurons in the molecular layer of the cortex and white matter.

CONCLUSIONS

Cortical resection is unlikely to be beneficial in these children due to the genetic defect and the unexpected neuropathological finding of mild diffuse malformations of cortical development. Together, these findings suggest a diffuse pathophysiological mechanism of the patients' epilepsy which will not respond to focal resective surgery.

Phenotypic and imaging features of FLNA-negative patients with bilateral periventricular nodular heterotopia and epilepsy

PURPOSE

Periventricular nodular heterotopia (PVNH) is a malformation of cortical development due to impaired neuronal migration resulting in the formation of nodular masses of neurons and glial cells in close proximity to the ventricular walls. We report the clinical characteristics of the largest case series of FLNA-negative patients with seizures and bilateral periventricular heterotopia.

METHODS

Participants were recruited through the Epilepsy Phenome/Genome Project (EPGP), a multicenter collaborative effort to collect detailed phenotypic data and DNA on a large number of individuals with epilepsy, including a cohort with symptomatic epilepsy related to PVNH. Included subjects had epilepsy, and MRI confirmed bilateral PVNH. Magnetic resonance imaging studies were visually and quantitatively reviewed to investigate the topographic extent of PVNH, symmetry, and laterality.

KEY FINDINGS

We analyzed data on 71 patients with bilateral PVNH. The incidence of febrile seizures was 16.6%. There was at least one other family member with epilepsy in 36.9% of this population. Developmental delay was present in 21.8%. Focal onset seizures were the most common type of seizure presentation (79.3%). High heterotopia burden was strongly associated with female gender and trigonal nodular localization. There was no evidence for differences in brain volume between PVNH subjects and controls. No relationship was observed between heterotopic volume and gender, developmental delay, location of PVNH, ventricular or cerebellar abnormalities, laterality of seizure onset, age at seizure onset, and duration of epilepsy.

SIGNIFICANCE

A direct correlation was observed between high heterotopia burden, female gender, and trigonal location in this large cohort of FLNA-negative bilateral PVNH patients with epilepsy. Quantitative MRI measurements indicated that this correlation is based on the diffuse nature of the heterotopic nodules rather than on the total volume of abnormal heterotopic tissue.

The genetics of the epilepsies

While genetic causes of epilepsy have been hypothesized from the time of Hippocrates, the advent of new genetic technologies has played a tremendous role in elucidating a growing number of specific genetic causes for the epilepsies. This progress has contributed vastly to our recognition of the epilepsies as a diverse group of disorders, the genetic mechanisms of which are heterogeneous. Genotype-phenotype correlation, however, is not always clear. Nonetheless, the developments in genetic diagnosis raise the promise of a future of personalized medicine. Multiple genetic tests are now available, but there is no one test for all possible genetic mutations, and the balance between cost and benefit must be weighed. A genetic diagnosis, however, can provide valuable information regarding comorbidities, prognosis, and even treatment, as well as allow for genetic counseling. In this review, we will discuss the genetic mechanisms of the epilepsies as well as the specifics of particular genetic epilepsy syndromes. We will include an overview of the available genetic testing methods, the application of clinical knowledge into the selection of genetic testing, genotype-phenotype correlations of epileptic disorders, and therapeutic advances as well as a discussion of the importance of genetic counseling.

Sudden infant death syndrome, sleep, and seizures

benign febrile seizures seen in 7% of infants before 6 months play a role in the terminal pathway in a subset of sudden infant death syndrome victims. Supporting evidence: (1) lack of 5-hydroxitryptamine, one consistent finding in sudden infant death syndrome that Kinney et al coined a developmental serotonopathy, is consistent with risk for seizures. (2) Non-rapid eye movement sleep increasing during the age of highest risk for sudden infant death syndrome facilitates some seizures (seizure gate). (3) Sudden unexpected death in epilepsy is associated with severe hypoxemia and hypercapnia during postictal generalized electroencephalographic (EEG) suppression. In toddlers, sudden unexplained deaths are associated with hippocampal abnormalities and some seizures. (4) The sudden nature of both deaths warrants an exploration of similarities in the terminal pathway. Moreover, sudden infant death syndrome, febrile seizures, sudden unexplained death in childhood, and sudden unexpected death in epilepsy share some of the following risk factors: prone sleeping, infections, hyperthermia, preterm birth, male gender, maternal smoking, and mutations in genes that regulate sodium channels. State-of-the-art molecular studies can be exploited to test this hypothesis.

SUDEP revisited - a decade on: have circumstances changed?

PURPOSE

A paper, published a decade ago, endorsed doctors' right to avoid discussing Sudden Unexpected Death in Epilepsy (SUDEP). It did not negate discussion, advocating same where appropriate. This paper investigates the current situation to identify any changes.

METHODS

The tort of negligence includes a duty to discuss "material risks" and adhere to accepted practice. Within the last decade, "material risks" for SUDEP have not altered significantly and international practice discusses SUDEP with those patients who seek advice or in whom such discussion is designed to improve patient compliance.

RESULTS

Doctors are unlikely to be found negligent for not discussing SUDEP, acknowledging a push encouraging same, despite it being contrary to routine practice in the US, Italy, UK and elsewhere. Doctors should continue to practice the "art of medicine", discuss SUDEP when warranted and with patients seeking such advice. They must warn about risks, such as bathing alone, avoiding accident and injuries and possibly SUDEP in non-compliant patients and also consider the impact of such discussion. With no 'material' changes in the last decade, doctors must recognise when to discuss SUDEP, with which patients and in what context, accepting it may have a negative psychosocial impact on family dynamics unless discussed in a culturally competent fashion, to avoid causing additional stress for families where accepting the diagnosis of epilepsy may already prove difficult.

CONCLUSION

Having formed a therapeutic relationship with the patient, discussion of SUDEP should be considered within that context, acknowledging the "art of medicine" and the implications of such discussion, similar to the situation a decade ago.

Mechanisms of sudden unexplained death in epilepsy

PURPOSE OF REVIEW

Human and experimental research has identified cardioautonomic and respiratory dysfunction as a frequent accompaniment in human and animal model events of sudden unexpected death in epilepsy (SUDEP). This review aims to provide an overview of the scientific evidence behind the currently accepted risk factors and working hypotheses regarding SUDEP pathophysiology.

RECENT FINDINGS

Epidemiological analysis of public health burden of SUDEP has shown that it rates second only to stroke in the years of potential life lost. Clinical and experimental studies uncovered the dynamic cardiorespiratory dysfunction interictally and imminently to SUDEP, and model systems have facilitated discoveries in SUDEP mechanistic understanding and application of pilot therapeutic interventions. Pilot molecular profiling of human SUDEP has uncovered complex genomic structure in the candidate gene network.

SUMMARY

Extensive clinical and experimental work has established a rationale for the conceptual thinking about SUDEP mechanisms. The application of the global molecular profiling will be invaluable in unraveling the individually unique genomic complexities and interactions that underlie the physiological signature of each patient. At the same time, sophisticated model systems will be critical in the iterative translation of human genetics, physiology, pharmacological interventions, and in testing preventive interventions.

Genomic biomarkers of SUDEP in brain and heart

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality, but how to predict which patients are at risk and how to prevent it remain uncertain. The underlying pathomechanisms of SUDEP are still largely unknown, but the general consensus is that seizures somehow disrupt normal cardiac or respiratory physiology leading to death. However, the proportion of SUDEP cases exhibiting cardiac or respiratory dysfunction as a critical factor in the terminal cascade of events remains unresolved. Although many general risk factors for SUDEP have been identified, the development of reliable patient-specific biomarkers for SUDEP is needed to provide more accurate risk prediction and personalized patient management strategies. Studies in animal models and patient groups have revealed at least nine different brain-heart genes that may contribute to a genetic susceptibility for SUDEP, making them potentially useful as genomic biomarkers. This review summarizes data on the relationship between these neurocardiac genes and SUDEP, discussing their brain-heart expression patterns and genotype-phenotype correlations in mouse models and people with epilepsy. These neurocardiac genes represent good first candidates for evaluation as genomic biomarkers of SUDEP in future studies. The development of validated reliable genomic biomarkers for SUDEP has the potential to transform the clinical treatment of epilepsy by pinpointing patients at risk of SUDEP and allowing optimized, genotype-guided therapeutic and prevention strategies.

CNS-disease affecting the heart: brain-heart disorders

There are a number of hereditary and non-hereditary central nervous system (CNS) disorders, which directly or indirectly affect the heart (brain-heart disorders). The most well-known of these CNS-disorders are epilepsy, stroke, subarachanoid bleeding, bacterial meningitis, and head injury. In addition, a number of hereditary and non-hereditary neurodegenerative disorders may impair cardiac functions. Affection of the heart may manifest as arrhythmias, cardiomyopathy, or autonomic dysfunction. Rarer cardiac complications of CNS disorders include heart failure, systolic or diastolic dysfunction, myocardial infarction, arterial hypertension, or pulmonary hypertension. Cardiomyopathy induced by hereditary CNS disease mainly include stress-induced myocardial dysfunction, known as Takotsubo syndrome (TTS). CNS disease triggering TTS includes epilepsy, ischemic stroke, subarachnoid bleeding, or PRES syndrome. Arrhythmias induced by hereditary CNS disease include supraventricular or ventricular arrhythmias leading to palpitations, dizziness, vertigo, fainting, syncope, (near) sudden cardiac death, or sudden unexplained death in epilepsy (SUDEP). Appropriate management of cardiac involvement in CNS-disorders is essential to improve outcome of affected patients.

Co-occurring malformations of cortical development and SCN1A gene mutations

OBJECTIVE

To report on six patients with SCN1A mutations and malformations of cortical development (MCDs) and describe their clinical course, genetic findings, and electrographic, imaging, and neuropathologic features.

METHODS

Through our database of epileptic encephalopathies, we identified 120 patients with SCN1A mutations, of which 4 had magnetic resonance imaging (MRI) evidence of MCDs. We collected two further similar observations through the European Task-force for Epilepsy Surgery in Children.

RESULTS

The study group consisted of five males and one female (mean age 7.4 ± 5.3 years). All patients exhibited electroclinical features consistent with the Dravet syndrome spectrum, cognitive impairment, and autistic features. Sequencing analysis of the SCN1A gene detected two missense, two truncating, and two splice-site mutations. Brain MRI revealed bilateral periventricular nodular heterotopia (PNH) in two patients and focal cortical dysplasia (FCD) in three, and disclosed no macroscopic abnormality in one. In the MRI-negative patient, neuropathologic study of the whole brain performed after sudden unexpected death in epilepsy (SUDEP), revealed multifocal micronodular dysplasia in the left temporal lobe. Two patients with FCD underwent epilepsy surgery. Neuropathology revealed FCD type IA and type IIA. Their seizure outcome was unfavorable. All four patients with FCD exhibited multiple seizure types, which always included complex partial seizures, the area of onset of which co-localized with the region of structural abnormality.

SIGNIFICANCE

MCDs and SCN1A gene mutations can co-occur. Although epidemiology does not support a causative role for SCN1A mutations, loss or impaired protein function combined with the effect of susceptibility factors and genetic modifiers of the phenotypic expression of SCN1A mutations might play a role. MCDs, particularly FCD, can influence the electroclinical phenotype in patients with SCN1A-related epilepsy. In patients with MCDs and a history of polymorphic seizures precipitated by fever, SCN1A gene testing should be performed before discussing any epilepsy surgery option, due to the possible implications for outcome.

Sleep abnormalities in children with Dravet syndrome

BACKGROUND

Mutations in the voltage-gated sodium channel SCN1A gene are responsible for the majority of Dravet syndrome cases. There is evidence that the Nav1.1 channel coded by the SCN1A gene is involved in sleep regulation. We evaluated sleep abnormalities in children with Dravet syndrome using nocturnal polysomnography.

METHODS

We identified six children at our institution with genetically confirmed Dravet syndrome who had also undergone formal sleep consultation with nocturnal polysomnography. Indications for polysomnography were parental concern of daytime fatigue or sleepiness, hyperactivity, inattention, disruptive behavior, nighttime awakenings, or nocturnal seizures. Sleep studies were scored according to guidelines of the American Academy of Sleep Medicine and non-rapid eye movement cyclic alternating pattern was visually identified and scored according to established methods.

RESULTS

The mean age of the subjects at the time of polysomnography was 6 years. Standard polysomnography did not show any consistent abnormalities in the obstructive or central apnea index, arousal index, sleep efficiency, or architecture. Cyclic alternating pattern analysis on five patients showed an increased mean rate of 50.3% (vs 31% to 34% in neurological normal children) with a mild increase in A1 subtype of 89.4% (vs 84.5%). A2/A3 subtype (5.3% vs 7.3%) and B phase duration (22.4 vs 24.7 seconds) were similar to previously reported findings in neurologically normal children.

CONCLUSION

Despite parental concerns for sleep disturbance in patients with Dravet syndrome, we could not identify abnormalities in sleep macroarchitecture. Non-rapid eye movement sleep microarchitecture was, however, abnormal, with increased A1 subtype, somewhat resembling a tracé alternant pattern of neonates and possibly suggestive of cortical synaptic immaturity in Dravet syndrome. Larger studies are needed to replicate these results.

The utility of exome sequencing for genetic diagnosis in a familial microcephaly epilepsy syndrome

Background

Despite remarkable advances in genetic testing, many adults with syndromic epilepsy remain without a molecular diagnosis. The challenge in providing genetic testing for this patient population lies in the extensive genetic heterogeneity associated with epilepsy. Even for the subset of epilepsy patients that present with a defining feature, such as microcephaly, the number of possible genes that would require interrogation by Sanger sequencing is extensive and often prohibitively expensive.

Case presentation

We report a family of French Canadian descent with four adult children affected with severe intellectual disability, epilepsy and microcephaly born to consanguineous parents and evaluated by the Genetics Service to provide informed genetic counseling to unaffected family members regarding possible recurrence risks. We used whole-exome sequencing (WES) of DNA from one affected sibling as a first-line diagnostic tool and compared the prioritization of variants using two strategies: 1) focusing on genes with homozygous variants; and, 2) focusing on genes associated with microcephaly. Both approaches prioritized the same homozygous novel frameshift mutation (p.Arg608Serfs*26) in WDR62, a gene known to cause autosomal recessive primary microcephaly. Sanger sequencing confirmed the presence of the homozygous mutation in the other three affected siblings.

Conclusions

WES and subsequent filtering of the rare variants in a single affected family member led to the rapid and cost-effective identification of a novel homozygous frameshift mutation in WDR62, thereby explaining the severe neurodevelopmental disorder in this family and facilitating genetic counseling. Our findings support WES as an effective first-line diagnostic tool in families presenting with rare genetically heterogeneous neurological disorders.

High-resolution molecular genomic autopsy reveals complex sudden unexpected death in epilepsy risk profile

Advanced variant detection in genes underlying risk of sudden unexpected death in epilepsy (SUDEP) can uncover extensive epistatic complexity and improve diagnostic accuracy of epilepsy-related mortality. However, the sensitivity and clinical utility of diagnostic panels based solely on established cardiac arrhythmia genes in the molecular autopsy of SUDEP is unknown. We applied the established clinical diagnostic panels, followed by sequencing and a high density copy number variant (CNV) detection array of an additional 253 related ion channel subunit genes to analyze the overall genomic variation in a SUDEP of the 3-year-old proband with severe myoclonic epilepsy of infancy (SMEI). We uncovered complex combinations of single nucleotide polymorphisms and CNVs in genes expressed in both neurocardiac and respiratory control pathways, including SCN1A, KCNA1, RYR3, and HTR2C. Our findings demonstrate the importance of comprehensive high-resolution variant analysis in the assessment of personally relevant SUDEP risk. In this case, the combination of de novo single nucleotide polymorphisms (SNPs) and CNVs in the SCN1A and KCNA1 genes, respectively, is suspected to be the principal risk factor for both epilepsy and premature death. However, consideration of the overall biologically relevant variant complexity with its extensive functional epistatic interactions reveals potential personal risk more accurately.

Sudden unexpected death in epilepsy: fatal post-ictal respiratory and arousal mechanisms

Sudden unexplained death in epilepsy (SUDEP) is the cause of premature death of up to 17% of all patients with epilepsy and as many as 50% with chronic refractory epilepsy. However, SUDEP is not widely recognized to exist. The etiology of SUDEP remains unclear, but growing evidence points to peri-ictal respiratory, cardiac, or autonomic nervous system dysfunction. How seizures affect these systems remains uncertain. Here we focus on respiratory mechanisms believed to underlie SUDEP. We highlight clinical evidence that indicates peri-ictal hypoxemia occurs in a large percentage of patients due to central apnea, and identify the proposed anatomical regions of the brain governing these responses. In addition, we discuss animal models used to study peri-ictal respiratory depression. We highlight the role 5-HT neurons play in respiratory control, chemoreception, and arousal. Finally, we discuss the evidence that 5-HT deficits contribute to SUDEP and sudden infant death syndrome and the striking similarities between the two.

Sudden unexpected death in epilepsy: from the lab to the clinic setting

Sudden unexpected death in epilepsy (SUDEP) is defined as sudden, unexpected, witnessed or unwitnessed, non-traumatic, and non-drowning death in a patient with epilepsy. Sudden unexpected death in epilepsy is probably the most common cause of epilepsy-related deaths. Many predisposing and initiating factors may coexist and contribute to SUDEP, but the mechanisms are poorly understood. Cardiac and respiratory deregulation seems to have a major role in SUDEP. Here, we review several advances in understanding the mechanisms involved in SUDEP.

Cardiac channel molecular autopsy: insights from 173 consecutive cases of autopsy-negative sudden unexplained death referred for postmortem genetic testing

OBJECTIVE

To perform long QT syndrome and catecholaminergic polymorphic ventricular tachycardia cardiac channel postmortem genetic testing (molecular autopsy) for a large cohort of cases of autopsy-negative sudden unexplained death (SUD).

METHODS

From September 1, 1998, through October 31, 2010, 173 cases of SUD (106 males; mean ± SD age, 18.4 ± 12.9 years; age range, 1-69 years; 89% white) were referred by medical examiners or coroners for a cardiac channel molecular autopsy. Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, a comprehensive mutational analysis of the long QT syndrome susceptibility genes (KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2) and a targeted analysis of the catecholaminergic polymorphic ventricular tachycardia type 1-associated gene (RYR2) were conducted.

RESULTS

Overall, 45 putative pathogenic mutations absent in 400 to 700 controls were identified in 45 autopsy-negative SUD cases (26.0%). Females had a higher yield (26/67 [38.8%]) than males (19/106 [17.9%]; P<.005). Among SUD cases with exercise-induced death, the yield trended higher among the 1- to 10-year-olds (8/12 [66.7%]) compared with the 11- to 20-year-olds (4/27 [14.8%]; P=.002). In contrast, for those who died during a period of sleep, the 11- to 20-year-olds had a higher yield (9/25 [36.0%]) than the 1- to 10-year-olds (1/24 [4.2%]; P=.01).

CONCLUSION

Cardiac channel molecular autopsy should be considered in the evaluation of autopsy-negative SUD. Several interesting genotype-phenotype observations may provide insight into the expected yields of postmortem genetic testing for SUD and assist in selecting cases with the greatest potential for mutation discovery and directing genetic testing efforts.

Migrating focal seizures during infancy: a case report and pathologic study

Migrating focal seizures in infancy are an unusual and often overlooked epilepsy syndrome, with onset before age 6 months, in which nearly continuous seizures involve multiple, independent areas of both hemispheres with an arrest of psychomotor development. We describe a patient with migrating focal seizures in infancy whose seizures began at age 45 days. The seizures were refractory to common antiepileptic drugs. At age 6 months, the infant received potassium bromide and became almost seizure-free. The infant developed severe neurologic impairment, with marked axial hypotonia and an absence of visual contact and head control. At age 8 months, the child suddenly died. Pathologic findings included multiple malformations of cortical development, polymicrogyria, and focal cortical dysplasia associated with hippocampal sclerosis.

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.

Genetic analysis of hyperpolarization-activated cyclic nucleotide-gated cation channels in sudden unexpected death in epilepsy cases

Sudden unexpected death in epilepsy (SUDEP) is the most common epilepsy-related cause of death, yet the cause is unknown. Our previous studies suggest a role for arrhythmia-related ion channel genes in the pathogenesis of SUDEP. Hyperpolarization-activated cyclic nucleotide-gated cation (HCN1-4) channels are ion channels involved in generating spontaneous rhythmic activity in cardiac pacemaker and neuronal cells. This study sought to determine the role of pathogenic DNA variants in the HCN1-4 genes in a large SUDEP cohort collected from 1993 to 2009. Post-mortem DNA samples were amplified and analyzed for each HCN exon. Genetic analysis in 48 SUDEP cases (age range 12-82 years) identified six novel and three previously reported nonsynonymous (amino acid changing) variants in HCN1 (n = 1), HCN2 (n = 2), HCN3 (n = 2) and HCN4 (n = 4). The Phe738Cys and Pro802Ser variants in HCN2, and Gly973Arg in HCN4 were absent in control alleles and affecting highly conserved residues in the carboxyl-cytoplasmic tail region. Our results support a pathogenic link between the heart and brain in SUDEP, mediated by the HCN neuro-cardiac ion channel genes.

Dravet syndrome as epileptic encephalopathy: evidence from long-term course and neuropathology

Dravet syndrome is an epilepsy syndrome of infantile onset, frequently caused by SCN1A mutations or deletions. Its prevalence, long-term evolution in adults and neuropathology are not well known. We identified a series of 22 adult patients, including three adult post-mortem cases with Dravet syndrome. For all patients, we reviewed the clinical history, seizure types and frequency, antiepileptic drugs, cognitive, social and functional outcome and results of investigations. A systematic neuropathology study was performed, with post-mortem material from three adult cases with Dravet syndrome, in comparison with controls and a range of relevant paediatric tissue. Twenty-two adults with Dravet syndrome, 10 female, were included, median age 39 years (range 20-66). SCN1A structural variation was found in 60% of the adult Dravet patients tested, including one post-mortem case with DNA extracted from brain tissue. Novel mutations were described for 11 adult patients; one patient had three SCN1A mutations. Features of Dravet syndrome in adulthood include multiple seizure types despite polytherapy, and age-dependent evolution in seizure semiology and electroencephalographic pattern. Fever sensitivity persisted through adulthood in 11 cases. Neurological decline occurred in adulthood with cognitive and motor deterioration. Dysphagia may develop in or after the fourth decade of life, leading to significant morbidity, or death. The correct diagnosis at an older age made an impact at several levels. Treatment changes improved seizure control even after years of drug resistance in all three cases with sufficient follow-up after drug changes were instituted; better control led to significant improvement in cognitive performance and quality of life in adulthood in two cases. There was no histopathological hallmark feature of Dravet syndrome in this series. Strikingly, there was remarkable preservation of neurons and interneurons in the neocortex and hippocampi of Dravet adult post-mortem cases. Our study provides evidence that Dravet syndrome is at least in part an epileptic encephalopathy.

Dravet syndrome and SCN1A gene mutation related-epilepsies: cognitive impairment and its determinants

Some studies have demonstrated that cognitive decline occurs in Dravet syndrome, starting shortly after the onset of seizures, rapidly progressing and then plateauing within a few years. It is unclear whether children that develop the syndrome had entirely normal cognitive skills before seizure onset, since subtle impairment easily escapes recognition in small infants. It is also difficult to demonstrate whether a recognisable profile of cognitive impairment or a definite behavioural phenotype exists. No clear-cut imaging or neuropathological marker or substrate has been recognised for cognitive impairment in this syndrome. However, there are different potentially causative factors, including the specific effects on the Nav1.1 channels caused by the underlying genic or genomic defect; frequent and prolonged convulsive and non-convulsive seizures or status epilepticus; recurrent subtle ictal phenomena, such as that accompanying pronounced visual sensitivity; the use of antiepileptic drugs with cognitive side effects, especially in heavy multiple-drug therapy; and the restrictions that children with severe epilepsy inevitably undergo.