In 1969, the International League Against Merlis, Dr. D. David Daly of Dallas, Dr. Epilepsy published a scheme for classifica- Dieter Janz of Berlin, Dr. J. Kiftin Penry of tion of epileptic seizures. Professor H. Bethesda, Dr. Carlo Alberto Tassinari of Gastaut, then Secretary-General of ILAE Marseille. In addition, Dr. Rudolph Dreyer and a member of the Commission on Clas- of Bethel. Dr. Antonio V. Escueta of Los sification, related the history of the work Angeles, Dr. K. F. Masuhr of Berlin, Dr. which represents a milestone in efforts at Richard H. Mattson of New Haven, Dr. classifying epileptic seizures and has led to Roger J. Porter of Bethesda. Dr. Dieter world-wide adoption (Gastaut, 1970). Schmidt of Berlin, and Dr. Gregory 0. Since the publication of the 1969 classifi- Walsh of Los Angeles attended as particication, objective and sophisticated methods pants and discussants in this workshop. for studying epileptic seizures have become In 1977, a workshop on generalized seicommonplace. These methods include zures was held in Berlin. The above Comvideo display of epileptic seizures on mag- mission members were present with the adnetic tape, the simultaneous recording of dition of Dr. Toyoji Wada of Shizuoka and the electroencephalogram using hard-wired invited participants who presented vidrecording techniques and radiotelemetry eotape data, including Dr. A. Cirignotta of with split screen display and instant replay Bologna, Dr. Peter Kellaway of Houston, capability. Dr. Cesare Lombroso of Boston, Dr. K. F. Since 1975, two further Commissions on Masuhr of Berlin, and Dr. D. Stefan of Classification and Terminology of the In- Bonn. The results of these workshops comternational League Against Epilepsy have prise the major portions of the version of convened in order to continue to update, the International Classification of Epileptic amend, and improve the classification in Seizures herewith proposed.

Proposal for Revised Clinical and ~lectro~nce~halo ~ra~hic Classification of Epileptic Seizures From the Commission on Classification and Terminology of the International League Against Epilepsy*

Objective To delineate the electroclinical features of SCN8A infantile developmental and epileptic encephalopathy (EIEE13, OMIM #614558). Methods Twenty-two patients, aged 19 months to 22 years, underwent electroclinical assessment. Results Sixteen of 22 patients had mildly delayed development since birth. Drug-resistant epilepsy started at a median age of 4 months, followed by developmental slowing, pyramidal/extrapyramidal signs (22/22), movement disorders (12/22), cortical blindness (17/22), sialorrhea, and severe gastrointestinal symptoms (15/22), worsening during early childhood and plateauing at age 5 to 9 years. Death occurred in 4 children, following extreme neurologic deterioration, at 22 months to 5.5 years. Nonconvulsive status epilepticus recurred in 14 of 22 patients. The most effective antiepileptic drugs were oxcarbazepine, carbamazepine, phenytoin, and benzodiazepines. EEG showed background deterioration, epileptiform abnormalities with a temporo-occipital predominance, and posterior delta/beta activity correlating with visual impairment. Video-EEG documented focal seizures (FS) (22/22), spasm-like episodes (8/22), cortical myoclonus (8/22), and myoclonic absences (1/22). FS typically clustered and were prolonged ( Conclusions: SCN8A developmental and epileptic encephalopathy has strikingly consistent electroclinical features, suggesting a global progressive brain dysfunction primarily affecting the temporo-occipital regions. Both uncontrolled epilepsy and developmental compromise contribute to the profound impairment (increasing risk of death) during early childhood, but stabilization occurs in late childhood.

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The phenotype of SCN8A developmental and epileptic encephalopathy.

Objective Epilepsy of infancy with migrating focal seizures (EIMFS) is one of the most severe developmental and epileptic encephalopathies. We delineate the genetic causes and genotype-phenotype correlations of a large EIMFS cohort. Methods Phenotypic and molecular data were analyzed on patients recruited through an international collaborative study. Results We ascertained 135 patients from 128 unrelated families. Ninety-three of 135 (69%) had causative variants (42/55 previously reported) across 23 genes, including 9 novel EIMFS genes: de novo dominant GABRA1, GABRB1, ATP1A3; X-linked CDKL5, PIGA; and recessive ITPA, AIMP1, KARS, WWOX. The most frequently implicated genes were KCNT1 (36/135, 27%) and SCN2A (10/135, 7%). Mosaicism occurred in 2 probands (SCN2A, GABRB3) and 3 unaffected mothers (KCNT1). Median age at seizure onset was 4 weeks, with earlier onset in the SCN2A, KCNQ2, and BRAT1 groups. Epileptic spasms occurred in 22% patients. A total of 127 patients had severe to profound developmental impairment. All but 7 patients had ongoing seizures. Additional features included microcephaly, movement disorders, spasticity, and scoliosis. Mortality occurred in 33% at median age 2 years 7 months. Interpretation We identified a genetic cause in 69% of patients with EIMFS. We highlight the genetic heterogeneity of EIMFS with 9 newly implicated genes, bringing the total number to 33. Mosaicism was observed in probands and parents, carrying critical implications for recurrence risk. EIMFS pathophysiology involves diverse molecular processes from gene and protein regulation to ion channel function and solute trafficking. ANN NEUROL 2019;86:821-831.

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The Genetic Landscape of Epilepsy of Infancy with Migrating Focal Seizures.

Identifying mutations in epilepsy genes: Impact on treatment selection.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.

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HCN1 mutation spectrum: from neonatal epileptic encephalopathy to benign generalized epilepsy and beyond

Targeted resequencing gene panels are used in the diagnostic setting to identify gene defects in epilepsy. We performed targeted resequencing using a 30-genes panel and a 95-genes panel in 349 patients with drug-resistant epilepsies beginning in the first years of life. We identified 71 pathogenic variants, 42 of which novel, in 30 genes, corresponding to 20.3% of the probands. In 66% of mutation positive patients seizures onset occurred before age 6 months. The 95-genes panel allowed a genetic diagnosis in 22 (6.3%) patients that would have otherwise been missed using the 30-gene panel. About 50% of mutations were identified in genes coding for sodium and potassium channel components. SCN2A was the most frequently mutated gene followed by SCN1A, KCNQ2, STXBP1, SCN8A, CDKL5 and MECP2. Twenty-nine mutations were identified in 23 additional genes, most of them recently associated with epilepsy. Our data show that panels targeting about 100 genes represent the best cost-effective diagnostic option in pediatric drug-resistant epilepsies. They enable molecular diagnosis of atypical phenotypes, allowing to broaden phenotype-genotype correlations. Molecular diagnosis might influence patient's management and translate into better and specific treatment recommendations in some conditions.

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Diagnostic Targeted Resequencing in 349 Patients with Drug‐Resistant Pediatric Epilepsies Identifies Causative Mutations in 30 Different Genes

We describe a mother and son with focal epilepsy, mild cognitive impairment, and pachygyria, which was parieto-occipital in the mother and with remarkable posterior greater than anterior severity in the son. Overall clinical manifestations, although overlapping in type, were likewise slightly more severe in the son. Using targeted resequencing through a gene panel for malformations of cortical development, we identified the c.655 T > A [p.(Trp219Arg)] novel missense variant in the LIS1 gene, segregating in the proband and in his mother. Western Blot analysis, qPCR gene expression and RT-PCR disclosed no significant differences between proband, his parents, and controls. Epilepsy and mild cognitive impairment can be the only clinical presentation of constitutional LIS1 mutations, which can therefore be inherited if the associated phenotype implies limited or no reproductive disadvantage. Parents of patients harboring LIS1 mutations should be assessed for their mutation carrier status.

Domenico Rutigliano

Papers

Diagnostic Targeted Resequencing in 349 Patients with Drug‐Resistant Pediatric Epilepsies Identifies Causative Mutations in 30 Different Genes

Familial dominant epilepsy and mild pachygyria associated with a constitutional LIS1 mutation.