Epilepsy Phenome/Genome Project Research Articles

Infantile Spasms of Unknown Cause: Who Can Have a Good Outcome?

Infantile spasms of unknown cause: predictors of outcome and genotype-phenotype correlation Yuskaitis CJ, Ruzhnikov MRZ, Howell KB, et al. Pediatr Neurol. 2018;87:48–56. doi:10.1016/j.pediatrneurol.2018.04.012. Epub 2018 May 7.Background:No large-scale studies have specifically evaluated the outcomes of infantile spasms (IS) of unknown cause, previously known as cryptogenic or idiopathic. The Epilepsy Phenome/Genome Project (EPGP) aimed to characterize IS of unknown cause by phenotype and genotype analysis.Methods:We undertook a retrospective multicenter observational cohort of 133 individuals within the EPGP database met criteria for IS of unknown cause with at least 6 months of follow-up data. Clinical medical records, imaging, and electroencephalography were examined.Results:Normal development occurred in only 15% of IS of unknown cause. The majority (85%) had clinically documented developmental delay (15% mild, 20% moderate, and 50% severe) at last assessment (median 2.7 years; interquartile interval 1.71-6.25 years). Predictors of positive developmental outcomes included no delay prior to IS (P < .001), older age of IS onset (median 6 months old), and resolution of IS after initial treatment (P < .001). Additional seizures after IS occurred in 67%, with predictors being seizures prior to IS (P = .018), earlier age of IS onset (median 5 months old), and refractory IS (P = .008). On a research basis, whole exome sequencing identified 15% with de novo variants in known epilepsy genes. Individuals with a genetic finding were more likely to have poor developmental outcomes (P = .035).Conclusions:The current study highlights the predominately unfavorable developmental outcomes and that subsequent seizures are common in children with IS of unknown cause. Ongoing genetic evaluation of IS of seemingly unknown cause is likely to yield a diagnosis and provide valuable prognostic information.

Gain-of-function HCN2 variants in genetic epilepsy.

Genetic generalized epilepsy (GGE) is a common epilepsy syndrome that encompasses seizure disorders characterized by spike-and-wave discharges (SWDs). Pacemaker hyperpolarization-activated cyclic nucleotide-gated channels (HCN) are considered integral to SWD genesis, making them an ideal gene candidate for GGE. We identified HCN2 missense variants from a large cohort of 585 GGE patients, recruited by the Epilepsy Phenome-Genome Project (EPGP), and performed functional analysis using two-electrode voltage clamp recordings from Xenopus oocytes. The p.S632W variant was identified in a patient with idiopathic photosensitive occipital epilepsy and segregated in the family. This variant was also independently identified in an unrelated patient with childhood absence seizures from a European cohort of 238 familial GGE cases. The p.V246M variant was identified in a patient with photo-sensitive GGE and his father diagnosed with juvenile myoclonic epilepsy. Functional studies revealed that both p.S632W and p.V246M had an identical functional impact including a depolarizing shift in the voltage dependence of activation that is consistent with a gain-of-function. In contrast, no biophysical changes resulted from the introduction of common population variants, p.E280K and p.A705T, and the p.R756C variant from EPGP that did not segregate with disease. Our data suggest that HCN2 variants can confer susceptibility to GGE via a gain-of-function mechanism.

Ictal fear: Associations with age, gender, and other experiential phenomena.

The aim of this study was to determine the relationship of fear to other auras and to gender and age using a large database. The Epilepsy Phenome/Genome Project (EPGP) is a multicenter, multicontinental cross-sectional study in which ictal symptomatology and other data were ascertained in a standardized series of questionnaires then corroborated by epilepsy specialists. Auras were classified into subgroups of symptoms, with ictal fear, panic, or anxiety as a single category. Of 536 participants with focal epilepsy, 72 were coded as having ictal fear/panic/anxiety. Reviewing raw patient responses, 12 participants were deemed not to have fear, and 24 had inadequate data, leaving 36 (7%) of 512 with definite ictal fear. In univariate analyses, fear was significantly associated with auras historically considered temporal lobe in origin, including cephalic, olfactory, and visceral complaints; déjà vu; and derealization. On both univariate and multivariate stepwise analyses, fear was associated with jamais vu and auras with cardiac symptoms, dyspnea, and chest tightening. Expressive aphasia was associated with fear on univariate analysis only, but the general category of aphasias was associated with fear only in the multivariate model. There was no age or gender relationship with fear when compared to the overall population with focal epilepsy that was studied under the EPGP. Patients with ictal fear were more likely to have a right hemisphere seizure focus. Ictal fear was strongly associated with other auras considered to originate from the limbic system. No relationship of fear with age or gender was observed.

Genetic effects on sleep/wake variation of seizures.

There is a complex bidirectional relationship between sleep and epilepsy. Sleep/wake timing of seizures has been investigated for several individual seizure types and syndromes, but few large-scale studies of the timing of seizures exist in people with varied epilepsy types. In addition, the genetic contributions to seizure timing have not been well studied. Sleep/wake timing of seizures was determined for 1,395 subjects in 546 families enrolled in the Epilepsy Phenome/Genome Project (EPGP). We examined seizure timing among subjects with different epilepsy types, seizure types, epilepsy syndromes, and localization. We also examined the familial aggregation of sleep/wake occurrence of seizures. Seizures in nonacquired focal epilepsy (NAFE) were more likely to occur during sleep than seizures in generalized epilepsy (GE), for both convulsive (odds ratio [OR] 5.2, 95% confidence interval [CI] 3.59-7.52) and nonconvulsive seizures (OR 4.2, 95% CI 2.48-7.21). Seizures occurring within 1 h of awakening were more likely to occur in patients with GE than with NAFE for both convulsive (OR 2.3, 95% CI 1.54-3.39) and nonconvulsive (OR 1.7, 95% CI 1.04-2.66) seizures. Frontal onset seizures were more likely than temporal onset seizures to occur during sleep. Sleep/wake timing of seizures in first-degree relatives predicted timing of seizures in the proband. We found that sleep/wake timing of seizures is associated with both epilepsy syndrome and seizure type. In addition, we provide the first evidence for a genetic contribution to sleep/wake timing of seizures in a large group of individuals with common epilepsy syndromes.

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

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. 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. 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. 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.

Surpassing the Target: How a Recruitment Campaign Transformed the Participant Accrual Trajectory in the Epilepsy Phenome/Genome Project.

Participant recruitment challenges pervade the majority of publicly funded clinical trials. However, little is known about methods for enhancing participant accrual. The Epilepsy Phenome/Genome Project (EPGP), a multicenter study funded by the National Institute of Neurological Disorders and Stroke (NINDS), aimed to enroll a total of 5,250 participants to better understand the genetic causes and phenotypic manifestations of epilepsy. However, similar to other trials, EPGP encountered recruitment challenges, and by the end of its first year, net enrollment was only 48% of the target for that time. To address this, EPGP established a National Participant Recruitment Campaign and began implementing and tracking the enrollment outcomes of a variety of proven and relatively novel recruitment methods. At the conclusion of the project, EPGP had successfully enrolled a total of 5,445 participants, thus surpassing its enrollment target. Data pertaining to EPGP's National Participant Recruitment Campaign was analyzed retrospectively, and the results are reported here, so that other multicenter trials may consider these methods in their recruitment planning and potentially avoid the costly repercussions of participant accrual issues.

Sex differences in seizure types and symptoms

BackgroundDespite the increasing interest in sex differences in disease manifestations and responses to treatment, very few data are available on sex differences in seizure types and semiology. The Epilepsy Phenome/Genome Project (EPGP) is a large-scale, multi-institutional, collaborative study that aims to create a comprehensive repository of detailed clinical information and DNA samples from a large cohort of people with epilepsy. We used this well-characterized cohort to explore differences in seizure types as well as focal seizure symptoms between males and females. MethodsWe reviewed the EPGP database and identified individuals with generalized epilepsy of unknown etiology (GE) (n=760; female: 446, male: 314), nonacquired focal epilepsy (NAFE) (n=476; female: 245, male: 231), or both (n=64; female: 33, male: 31). Demographic data along with characterization of seizure type and focal seizure semiologies were examined. ResultsIn GE, males reported atonic seizures more frequently than females (6.5% vs. 1.7%; p<0.001). No differences were observed in other generalized seizure types. In NAFE, no sex differences were seen for seizure types with or without alteration of consciousness or progression to secondary generalization. Autonomic (16.4% vs. 26.6%; p=0.005), psychic (26.7% vs. 40.3%; p=0.001), and visual (10.3% vs. 19.9%; p=0.002) symptoms were more frequently reported in females than males. Specifically, of psychic symptoms, more females than males endorsed déjà vu (p=0.001) but not forced thoughts, derealization/depersonalization, jamais vu, or fear. With corrections for multiple comparisons, there were no significant differences in aphasic, motor, somatosensory, gustatory, olfactory, auditory, vertiginous, or ictal headache symptoms between sexes. ConclusionsSignificant differences between the sexes were observed in the reporting of atonic seizures, which were more common in males with GE, and for autonomic, visual, and psychic symptoms associated with NAFE, which were more common in females.

Auras in generalized epilepsy.

We studied the frequency of auras in generalized epilepsy (GE) using a detailed semistructured diagnostic interview. In this cross-sectional study, participants with GE were drawn from the Epilepsy Phenome/Genome Project (EPGP). Responses to the standardized diagnostic interview regarding tonic-clonic (grand mal) seizures were then examined. This questionnaire initially required participants to provide their own description of any subjective phenomena before their "grand mal seizures." Participants who provided answers to these questions were considered to have an aura. All participants were then systematically queried regarding a list of specific symptoms occurring before grand mal seizures, using structured (closed-ended) questions. Seven hundred ninety-eight participants with GE were identified, of whom 530 reported grand mal seizures. Of these, 112 (21.3%) reported auras in response to the open-ended question. Analysis of responses to the closed-ended questions suggested that 341 participants (64.3%) experienced at least one form of aura. Auras typically associated with focal epilepsy were reported by a substantial proportion of EPGP subjects with GE. This finding may support existing theories of cortical and subcortical generators of GE with variable spread patterns. Differences between responses to the open-ended question and closed-ended questions may also reflect clinically relevant variation in patient responses to history-taking and surveys. Open-ended questions may underestimate the prevalence of specific types of auras and may be in part responsible for the underrecognition of auras in GE. In addition, structured questions may influence participants, possibly leading to a greater representation of symptoms.

Lennox‐Gastaut syndrome of unknown cause: Phenotypic characteristics of patients in theEpilepsyPhenome/GenomeProject

Lennox-Gastaut syndrome (LGS) is a devastating childhood-onset epilepsy syndrome. The cause is unknown in 25% of cases. Little has been described about the specific clinical or electroencephalography (EEG) features of LGS of unknown or genetic cause (LGS(u)). The Epilepsy Phenome/Genome Project (EPGP) aims to characterize LGS(u) by phenotypic analysis of patients with LGS(u) and their parents. One hundred thirty-five patients with LGS with no known etiology and their parents were enrolled from 19 EPGP centers in the United States and Australia. Clinical data from medical records, standardized questionnaires, imaging, and EEG were collected with use of online informatics systems developed for EPGP. LGS(u) in the EPGP cohort had a broad range of onset of epilepsy from 1 to 13 years, was male predominant (p < 0.0002), and was associated with normal development prior to seizure onset in 59.2% of patients. Despite the diagnosis, almost half of the adult patients with LGS(u) completed secondary school. Parents were cognitively normal. All subjects had EEG recordings with generalized epileptiform abnormalities with a spike wave frequency range of 1-5 Hz (median 2 Hz), whereas 8.1% of subjects had EEG studies with a normal posterior dominant rhythm. Almost 12% of patients evolved from West syndrome. LGS(u) has distinctive characteristics including a broad age range of onset, male predominance, and often normal development prior to the onset of seizures. Cognitive achievements such as completion of secondary school were possible in half of adult patients. Our phenotypic description of LGS(u) coupled with future genetic studies will advance our understanding of this epilepsy syndrome.

Racial and ethnic differences in epilepsy classification among probands in the Epilepsy Phenome/Genome Project (EPGP)

Little is known about the ethnic and racial differences in the prevalence of generalized and focal epilepsy among patients with non-acquired epilepsies. In this study, we examined epilepsy classification and race/ethnicity in 813 probands from sibling or parent-child pairs with epilepsy enrolled in the Epilepsy Genome/Phenome Project (EPGP). Subjects were classified as generalized epilepsy (GE), non-acquired focal epilepsy (NAFE), mixed epilepsy syndrome (both generalized and focal), and unclassifiable, based on consensus review of semiology and available clinical, electrophysiology, and neuroimaging data. In this cohort, 628 (77.2%) subjects identified exclusively as Caucasian/white and 65 (8.0%) subjects reported African ancestry, including subjects of mixed-race. Of the Caucasian/white subjects, 357 (56.8%) had GE, 207 (33.0%) had NAFE, 32 (5.1%) had a mixed syndrome, and 32 (5.1%) were unclassifiable. Among subjects of African ancestry, 28 (43.1%) had GE, 27 (41.5%) had NAFE, 2 (3.1%) had a mixed syndrome, and 8 (12.3%) were unclassifiable. There was a higher proportion of subjects with GE compared to other syndromes among Caucasians/whites compared to subjects with African ancestry (OR 1.74, 95% CI: 1.04-2.92, two-tailed Fisher's exact test, p=0.036). There was no difference in the rate of GE among subjects reporting Hispanic ethnicity (7.6% of total) when adjusted for race (Caucasian/white vs non-Caucasian/white; OR 0.65, 95% CI: 0.40-1.06, p>0.05). The proportion of participants with unclassifiable epilepsy was significantly greater in those of African-American descent. In a group of patients with epilepsy of unknown etiology and an affected first degree relative, GE is more common among Caucasian/white subjects than among those with African ancestry. These findings suggest there may be geographical differences in the distribution of epilepsy susceptibility genes and an effect of genetic background on epilepsy phenotype. However, the results should be interpreted with caution because of the low numbers of African-Americans in this cohort and more limited diagnostic data available for epilepsy classification in these subjects compared to Caucasians/whites.

The Epilepsy Phenome/Genome Project

Epilepsy is a common neurological disorder that affects approximately 50 million people worldwide. Both risk of epilepsy and response to treatment partly depend on genetic factors, and gene identification is a promising approach to target new prediction, treatment, and prevention strategies. However, despite significant progress in the identification of genes causing epilepsy in families with a Mendelian inheritance pattern, there is relatively little known about the genetic factors responsible for common forms of epilepsy and so-called epileptic encephalopathies. Study design The Epilepsy Phenome/Genome Project (EPGP) is a multi-institutional, retrospective phenotype-genotype study designed to gather and analyze detailed phenotypic information and DNA samples on 5250 participants, including probands with specific forms of epilepsy and, in a subset, parents of probands who do not have epilepsy. EPGP is being executed in four phases: study initiation, pilot, study expansion/establishment, and close-out. This article discusses a number of key challenges and solutions encountered during the first three phases of the project, including those related to (1) study initiation and management, (2) recruitment and phenotyping, and (3) data validation. The study has now enrolled 4223 participants. EPGP has demonstrated the value of organizing a large network into cores with specific roles, managed by a strong Administrative Core that utilizes frequent communication and a collaborative model with tools such as study timelines and performance-payment models. The study also highlights the critical importance of an effective informatics system, highly structured recruitment methods, and expert data review.

Evidence for a shared genetic susceptibility to migraine and epilepsy

Although epilepsy and migraine are known to co-occur within individuals, the contribution of a shared genetic susceptibility to this comorbidity remains unclear. We investigated the hypothesis of shared genetic effects on migraine and epilepsy in the Epilepsy Phenome/Genome Project (EPGP) cohort. We studied prevalence of a history of migraine in 730 EPGP participants aged ≥ 12 years with nonacquired focal epilepsy (NAFE) or generalized epilepsy (GE) from 501 families containing two or more individuals with epilepsy of unknown cause. Information on migraine without aura (MO) and migraine with aura (MA) was collected using an instrument validated for individuals ≥ 12 years. Because many individuals have both MO and MA, we considered two nonoverlapping groups of individuals with migraine: those who met criteria for MA in any of their headaches (MA), and those who did not ("MO-only"). EPGP participants were interviewed about the history of seizure disorders in additional nonenrolled family members. We evaluated associations of migraine prevalence in enrolled subjects with a family history of seizure disorders in additional nonenrolled relatives, using generalized estimating equations to control for the nonindependence of observations within families. Prevalence of a history of MA (but not MO-only) was significantly increased in enrolled participants with two or more additional affected first-degree relatives. These findings support the hypothesis of a shared genetic susceptibility to epilepsy and MA.

The Epilepsy Phenome/Genome Project (EPGP) informatics platform

BackgroundThe Epilepsy Phenome/Genome Project (EPGP) is a large-scale, multi-institutional, collaborative network of 27 epilepsy centers throughout the U.S., Australia, and Argentina, with the objective of collecting detailed phenotypic and genetic data on a large number of epilepsy participants. The goals of EPGP are (1) to perform detailed phenotyping on 3750 participants with specific forms of non-acquired epilepsy and 1500 parents without epilepsy, (2) to obtain DNA samples on these individuals, and (3) to ultimately genotype the samples in order to discover novel genes that cause epilepsy. To carry out the project, a reliable and robust informatics platform was needed for standardized electronic data collection and storage, data quality review, and phenotypic analysis involving cases from multiple sites. MethodsEPGP developed its own suite of web-based informatics applications for participant tracking, electronic data collection (using electronic case report forms/surveys), data management, phenotypic data review and validation, specimen tracking, electroencephalograph and neuroimaging storage, and issue tracking. We implemented procedures to train and support end-users at each clinical site. ResultsThus far, 3780 study participants have been enrolled and 20,957 web-based study activities have been completed using this informatics platform. Over 95% of respondents to an end-user satisfaction survey felt that the informatics platform was successful almost always or most of the time. ConclusionsThe EPGP informatics platform has successfully and effectively allowed study management and efficient and reliable collection of phenotypic data. Our novel informatics platform met the requirements of a large, multicenter research project. The platform has had a high level of end-user acceptance by principal investigators and study coordinators, and can serve as a model for new tools to support future large scale, collaborative research projects collecting extensive phenotypic data.