Electroclinical Phenotype Research Articles

Familial focal epilepsy with focal cortical dysplasia due to DEPDC5 mutations.

The DEPDC5 (DEP domain-containing protein 5) gene, encoding a repressor of the mTORC1 signaling pathway, has recently emerged as a major gene mutated in familial focal epilepsies. We aimed to further extend the role of DEPDC5 to focal cortical dysplasias (FCDs). Seven patients from 4 families with DEPDC5 mutations and focal epilepsy associated with FCD were recruited and investigated at the clinical, neuroimaging, and histopathological levels. The DEPDC5 gene was sequenced from genomic blood and brain DNA. All patients had drug-resistant focal epilepsy, 5 of them underwent surgery, and 1 had a brain biopsy. Electroclinical phenotypes were compatible with FCD II, although magnetic resonance imaging (MRI) was typical in only 4 cases. Histopathology confirmed FCD IIa in 2 patients (including 1 MRI-negative case) and showed FCD I in 2 other patients, and remained inconclusive in the last 2 patients. Three patients were seizure-free postsurgically, and 1 had a worthwhile improvement. Sequencing of blood DNA revealed truncating DEPDC5 mutations in all 4 families; 1 mutation was found to be mosaic in an asymptomatic father. A brain somatic DEPDC5 mutation was identified in 1 patient in addition to the germline mutation. Germline, germline mosaic, and brain somatic DEPDC5 mutations may cause epilepsy associated with FCD, reinforcing the link between mTORC1 pathway and FCDs. Similarly to other mTORopathies, a "2-hit" mutational model could be responsible for cortical lesions. Our study also indicates that epilepsy surgery is a valuable alternative in the treatment of drug-resistant DEPDC5-positive focal epilepsies, even if the MRI is unremarkable.

Brief asymmetric tonic posturing with diffuse low-voltage fast activity in seizures arising from the mesial parietal region

Seizures originating from the parietal lobe can demonstrate variable semiology. Our aim was to describe the electroclinical features of seizures originating from the mesial parietal lobe. We identified four patients through the Comprehensive Epilepsy Program at our institution, who had strong evidence of a mesial parietal source for their epilepsy, including a mesial parietal structural lesion. Patients had very frequent brief seizures despite anticonvulsants, each lasting 10-30s, with rapid return of awareness post-event. Clinically attacks were bland, or showed asymmetric tonic posturing, often with partially preserved awareness. Ictal EEG showed diffuse low voltage fast activity. Seizures arising from the precuneus, in the mesial parietal lobe, appear to have a recognizable electroclinical phenotype. Although the clinical and EEG features might have been considered 'non-localizing', there is a striking similarity across patients. The precuneus is a key component of the default mode network (DMN), important for internal reflective thinking. Deactivation of this region has been found to be a prominent feature of generalized spike and wave epileptiform activity. The seizure semiology of these patients presumably reflects activation of this region, and ictal propagation along intrinsically connected components of the DMN.

Seizures and EEG features in 74 patients with genetic-dysmorphic syndromes.

Epilepsy is one of the most common findings in chromosome aberrations. Types of seizures and severity may significantly vary both between different conditions and within the same aberration. Hitherto specific seizures and EEG patterns are identified for only few syndromes. We studied 74 patients with defined genetic-dysmorphic syndromes with and without epilepsy in order to assess clinical and electroencephalographic features, to compare our observation with already described electro-clinical phenotypes, and to identify putative electroencephalographic and/or seizure characteristics useful to address the diagnosis. In our population, 10 patients had chromosomal disorders, 19 microdeletion or microduplication syndromes, and 32 monogenic syndromes. In the remaining 13, syndrome diagnosis was assessed on clinical grounds. Our study confirmed the high incidence of epilepsy in genetic-dysmorphic syndromes. Moreover, febrile seizures and neonatal seizures had a higher incidence compared to general population. In addition, more than one third of epileptic patients had drug-resistant epilepsy. EEG study revealed poor background organization in 42 patients, an excess of diffuse rhythmic activities in beta, alpha or theta frequency bands in 34, and epileptiform patterns in 36. EEG was completely normal only in 20 patients. No specific electro-clinical pattern was identified, except for inv-dup15, Angelman, and Rett syndromes. Nevertheless some specific conditions are described in detail, because of notable differences from what previously reported. Regarding the diagnostic role of EEG, we found that--even without any epileptiform pattern--the generation of excessive rhythmic activities in different frequency bandwidths might support the diagnosis of a genetic syndrome.

Mesial Temporal Lobe Epilepsy: A Distinct Electroclinical Subtype of Temporal Lobe Epilepsy

ABSTRACT.Mesial temporal lobe epilepsy is a common subtype of temporal lobe epilepsy. Its most common cause is hippocampal sclerosis, which contributes to its distinct electroclinical phenotype that is seen commonly in the epilepsy monitoring unit setting. The common electrophysiological data show anterior temporal interictal sharp waves as well as rhythmic theta activity in the same localization. While the electrophysiological data can at times be misleading, its stereotyped and characteristic semiology can often allow for accurate diagnosis on its own. As patients with mesial temporal lobe epilepsy often fail medical therapy, surgical therapy can be considered. Early accurate diagnosis in these patients is essential for optimal care.

Co-occurring malformations of cortical development and SCN1A gene mutations.

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. 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. 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. 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.

Late onset epileptic spasms is frequent in MECP2 gene duplication: Electroclinical features and long-term follow-up of 8 epilepsy patients

Mutation of the X-linked methyl CpG binding protein 2 (MECP2) has been first identified as the cause of Rett syndrome. More recently, MECP2 gene duplication syndrome has been identified in males. The MECP2 duplication syndrome is characterized by severe mental retardation, infantile hypotonia, progressive spasticity and recurrent infections. Epileptic seizures are inconstant but poorly described. The aim of the study is to describe the electroclinical features of epilepsy in MECP2 duplication patients in order to refine the epilepsy phenotype and its evolution. MethodsWe conducted a retrospective study in four child neurology departments in France. Eight boys with a MECP2 gene duplication and epilepsy were retrospectively studied. We evaluated both clinical and electroencephalographic data before seizure onset, at seizure onset and during the follow-up. ResultsThe patients started seizures at the median age of 6 years (range: 2.5–17 years). Half exhibits late onset epileptic spasms while the other exhibit either focal epilepsy or unclassified generalized epilepsy. Before seizure onset, EEGs were abnormal in all patients showing a slowing of the background or a normal background with fast activities, while EEG performed in epileptic patients, showed a slowing of the background in 6/8 and localized slow or sharp waves in 7/8. Most patients (6/8) have evolved to drug resistant epilepsy. ConclusionAlthough late onset epileptic spasms are common in patients with MECP2 duplication, no specific electroclinical phenotype emerges, probably due to genetic heterogeneity of the syndrome. Further studies are needed to individualize specific epileptic subtype in larger cohort of patients.

Migrating partial seizures of infancy: delineation of the clinical and genetic features in a national patient cohort

BackgroundMigrating partial seizures of infancy (MPSI) is a severe, pharmacoresistant, early-onset epilepsy syndrome associated with high morbidity and mortality in which the underlying causal disease mechanisms are poorly understood. We aimed to describe the clinical, radiological, and pathological features of a national cohort of patients and to investigate the genetic basis of the syndrome. MethodsWe did a national surveillance study with data from the British Paediatric Neurology Surveillance Unit, with detailed endophenotyping on the referred cases. The genetic approaches that we took for molecular genetic investigation were: multiple gene panel testing of 29 genes associated with early-onset epilepsy, whole exome sequencing, and direct Sanger sequencing of KCNT1, a recently identified cause of MPSI. The multiple gene panel used Haloplex sequence capture (Agilent, Santa Clara, CA, USA) and Illumina sequencing with a MiSeq platform. For copy number variant analysis we used a custom Roche Nimblegen oligonucleotide 135K aCGH (Roche Diagnostic Ltd, Madison, WI, USA). We analysed sequence data using NextGENe software (Softgenetics, State College, PA USA) and array data using CGH Fusion (InfoQuant, London, UK). We did whole exome sequencing using Illumina paired-end library preparation and sequencing on a Hi-Seq platform. For Sanger sequencing, the genomic KCNT1 DNA sequence was taken from Ensembl and primer pairs for all exons, and flanking intronic regions were designed with primer3 software. Exons were amplified by PCR, sequenced by the BigDye terminator method, and analysed with Chromas/Sequencher software. The research genetic study was approved by the local research ethics committee and specific consent was given by individual parents for genetic studies to be undertaken on a research basis. Findings14 patients met the electroclinical criteria for a diagnosis of MPSI. Several novel clinical findings (movement disorder and severe gut dysmotility) and electrographic features (hypsarrhythmia, burst suppression) were identified. Novel radiological features included delayed myelination in five patients with white matter hyperintensity on brain MRI in four, and decreased N-acetyl aspartate on magnetic resonance spectroscopy in three of four patients. Putaminal atrophy, evident in one patient, has not been previously reported. Neuropathological findings included bilateral hippocampal gliosis and neuronal loss in two patients who had post-mortem examinations. Genetic investigation showed missense mutations of KCNT1 in three of the nine patients tested. One variant c.2800G>A (p.A934T) was found in several patients and likely to be a common mutation for KCNT1-MPSI. Another mutation, c.811G>T (p.V271F), is a novel, previously unreported variant, which is highly conserved, absent in control populations, and is predicted to be damaging (Polyphen score 0·733). InterpretationThis study is the first national cohort of patients with this rare condition and expands the electroclinical phenotype of MPSI. We have shown that KCNT1 is an important disease-causing gene in MPSI. However the absence of KCNT1 mutations in many patients suggests that this condition is genetically heterogeneous and further genetic causes are yet to be discovered. FundingNeurology Charitable Fund (Alder Hey Children's Hospital), MPSI support group, Action Medical Research, UK Children's Neurological Research Campaign, Roald Dahl's Marvellous Children's Charity, Great Ormond Street Hospital Children's Charities.

Características electroclínicas de un paciente con síndrome del cromosoma 20 en anillo

The ring chromosome 20 syndrome (r20) is a rare genetic disorder with a late diagnosis. A 17 year old boy with drug-resistant epilepsy of 14 years of evolution, which has moderate mental retardation, behavioral alterations and seizures consisting of complex non-convulsive status and generalized seizures during wakefulness, along with more subtle epileptic manifestations during sleep. Karyotype in peripheral blood showed the existence of a ring chromosome 20, whose breakpoints were p13q13.3, presenting a mosaicism 46,XY[23]/46,XY,r(20)(p13q13.3)[25]. The epileptic r20 syndrome seems to have a characteristic electroclinical phenotype and, although not pathognomonic, should be sufficient for all patients who meet a karyotype in peripheral blood, thus avoiding multiple trials with unnecessary drugs and exhaustive studies. In this sense, the study of sleep EEG may be helpful.

KCNQ2 encephalopathy: Delineation of the electroclinical phenotype and treatment response

Neonatal-onset epilepsies are rare conditions, mostly genetically determined, that can have a benign or severe phenotype.(1,2) There is recent recognition of de novo KCNQ2 mutations in patients with severe neonatal-onset epilepsy with intractable seizures and severe psychomotor impairment, termed KCNQ2 encephalopathy.(3,4) This is a rare condition and all patients reported so far were diagnosed well after the neonatal period.(3,4) We report on 3 new cases of KCNQ2 encephalopathy diagnosed in the neonatal period and studied with continuous video-EEG recording. We describe a distinct electroclinical phenotype and report on efficacy of antiepileptic drug (AED) therapies.

Epileptic encephalopathy as models of system epilepsy

The pathophysiology of epileptic encephalopathies has long been debated. Recently, some authors proposed the new concept of so-called system epilepsies. This hypothesis postulates that system epilepsies are produced by the enduring propensity to generate seizures in different cerebral areas that, alone, are unable to create a specific electroclinical phenotype. This goes beyond the classical dichotomy between focal and generalized epilepsy. Epileptic encephalopathies, in general, have the ideal profile to be considered as system epilepsies, and West syndrome and Lennox-Gastaut syndrome are two of the best examples. Apart from the conventional neurophysiologic methods for studying brain activities and the pathophysiologic mechanisms underlying epileptic syndromes, other new methods of neuroimaging support this hypothesis.

Epilepsy in Mowat‐Wilson syndrome: Is it a matter of GABA?

We have read with interest the latest advances regarding ZEB2 gene function in neuroembryology and its connections with epilepsy (McKinsey et al., 2013; Van den Berghe et al., 2013). Zinc finger E-box binding homeobox 2 (ZEB2, MIM#60580), also annotated as ZFHX1B and SIP1, is a member of the two-handed zinc finger/homeodomain transcription factors. Its role during development has been confirmed by invalidation in mice, which revealed arrest of embryonic development with severe neural plate and somatogenesis defects, as well as migratory failure of neural crest cells (Van de Putte et al., 2003). In humans, deletions or mutations of ZEB2 cause the Mowat-Wilson syndrome (MWS), which is characterized by a distinctive facial appearance, intellectual disability, and variable other features including agenesis of the corpus callosum and Hirschsprung disease (Mowat et al., 2003). Epilepsy is one of the main features of MWS, with a prevalence of about 70–75%. We recently delineated the electroclinical phenotype of epilepsy in MWS. In these patients, epilepsy is usually characterized by frontal lobe and atypical absence seizures, often preceded by fever-triggered seizures; in addition, we observed an age-dependent electroencephalography (EEG) pattern with frequent diffuse frontal dominant spike and wave discharges during the awake state and a near to continuous spike and wave activity during slow sleep (Cordelli et al., 2013). Some authors suggested that epilepsy in MWS could be the result of cerebral malformations (Engenheiro et al., 2008). Instead, we noticed that MRI did not disclose any cortical malformations clearly associated with epilepsy and that the electroclinical pattern (which was present irrespective of magnetic resonance imaging [MRI] findings) suggested an age-related disorder with a genetic, rather than a structural-malformative, etiology. Meanwhile, McKinsey and Van den Berghe et al. demonstrated the influence of ZEB2 on the neurogenesis of cortical γ-aminobutyric acid (GABA)ergic interneurons. Their studies highlight that the lack of ZEB2 prevents the repression of NKX2-1 homeobox transcription factor, the expression of which provokes the differentiation of the progenitors in striatal interneurons rather than cortical ones. Deficit of GABAergic inhibition is supposed to underlie most forms of seizures, including focal and absence seizures (Yalçın, 2012). However, results of GABAergic inhibition are brain-area and inhibitory-pathway specific. In fact, within one brain region, at a given time of life, some modifications in these circuitries will appear as proepileptic and others as antiepileptic (Bernard et al., 2000). Therefore, the switch between cortical and striatal GABAergic interneurons determined by mutations of ZEB2 could suggest a mechanism for the epilepsy observed in MWS, as proposed by McKinsey and Van den Berghe. From our point of view, that is the one of the clinicians, we strongly support this hypothesis, as the age-related electroclinical pattern we have detected in vivo is reminiscent of the idea of a genetic form of epilepsy and is scarcely influenced by brain macroanatomy. In conclusion, we feel that these observations could be of high importance in understanding how epilepsy is determined in patients with MWS. New interesting scenarios in terms of treatment are now opened. The authors declare no conflict of interest. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

Electroclinical phenotypes in a pedigreed baboon colony

This is the first large-scale epidemiological study evaluating the prevalence of interictal epileptic discharges (IEDs) and photosensitivity (PS) recorded by scalp EEG in a natural nonhuman-primate model of photosensitive, generalized epilepsy. Scalp EEG was used to characterize electroclinical phenotypes in a large baboon pedigree housed at the Southwest National Primate Research Center at the Texas Biomedical Research Institute (Texas Biomed) based upon IEDs and photosensitivity. Scalp EEG studies including intermittent light stimulation (ILS) were performed in 671 baboons. Clinical histories were available for 531 (79%) of the animals. The EEG studies lasted 53 (±11) min, during which the baboons were lightly sedated with intramuscular ketamine doses of 5.6 (±0.8) mg. The animals were further classified according to electroclinical phenotypes recorded by scalp EEG: presence or absence of IEDs, seizures and photoparoxysmal or photoconvulsive responses. Effects of age, gender, and species on EEG phenotypes were compared using (Chi-square, two-sided, α<0.05). Sensitivity and specificity of IEDs and photosensitivity to detect a history of seizures was calculated. Generalized IEDs and photosensitivity were identified in 324 (49%) and 156 (23%) pedigreed baboons, respectively. Only photosensitivity was associated with gender, significantly increased in males. Otherwise, while IEDs were marginally more prevalent among males, there were no other significant associations of IEDs or photosensitivity with age or subspecies. Photosensitivity was significantly associated with IEDs, with demonstrating a possible association with gender and subspecies. Of 531 baboons with histories of clinical events, 91 (17%) had witnessed seizures and 269 (51%) were asymptomatic. IEDs demonstrated sensitivity and specificity of 62% and 57%, and photosensitivity of 40% and 83%, for prediction of seizures, respectively. While these EEG findings mirror the high prevalence of seizures in the colony, the sensitivity and specificity of scalp EEG may have been affected by ketamine's ability to lower the threshold for IEDs and seizures, particularly in animals predisposed to epilepsy. Photosensitivity provides a specific biological marker for epilepsy in future epidemiological, genetic, behavioral and histopathological studies.

Neonatal suppression‐burst without epileptic seizures: expanding the electroclinical phenotype of STXBP1‐related, early‐onset encephalopathy

Early-onset epileptic encephalopathies (EOEEs) are characterised by epileptic seizures beginning in the first months of life, abnormal background EEG activity, and are associated with severe developmental delay and poor prognosis. Mutations and deletions in the STXBP1 gene are associated with Ohtahara syndrome, also known as "early infantile epileptic encephalopathy". We report an infant affected by EOEE with a 9q34.11 deletion that encompassed the genes STXBP1 and SPTAN1. The infant presented with neonatal encephalopathy without epileptic seizures and an EEG pattern varying from highly discontinuous to suppression-burst. This was followed by West syndrome at 2 months with atypical hypsarrhythmia and spasms, easily controlled by therapy. Our findings suggest that molecular analysis of STXBP1 should be considered for newborns affected by neonatal encephalopathy associated with a peculiar EEG pattern, even in the absence of neonatal epileptic seizures.

Epilepsy in Mowat–Wilson syndrome: Delineation of the electroclinical phenotype

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene and is characterized by distinctive facial features, epilepsy, moderate to severe intellectual disability, corpus callosum abnormalities and other congenital malformations. Epilepsy is considered a main manifestation of the syndrome, with a prevalence of about 70-75%. In order to delineate the electroclinical phenotype of epilepsy in MWS, we investigated epilepsy onset and evolution, including seizure types, EEG features, and response to anti-epileptic therapies in 22 patients with genetically confirmed MWS. Onset of seizures occurred at a median age of 14.5 months (range: 1-108 months). The main seizure types were focal and atypical absence seizures. In all patients the first seizure was a focal seizure, often precipitated by fever. The semiology was variable, including hypomotor, versive, or focal clonic manifestations; frequency ranged from daily to sporadic. Focal seizures were more frequent during drowsiness and sleep. In 13 patients, atypical absence seizures appeared later in the course of the disease, usually after the age of 4 years. Epilepsy was usually quite difficult to treat: seizure freedom was achieved in nine out of the 20 treated patients. At epilepsy onset, the EEGs were normal or showed only mild slowing of background activity. During follow-up, irregular, diffuse frontally dominant and occasionally asymmetric spike and waves discharges were seen in most patients. Sleep markedly activated these abnormalities, resulting in continuous or near-to-continuous spike and wave activity during slow wave sleep. Slowing of background activity and poverty of physiological sleep features were seen in most patients. Our data suggest that a distinct electroclinical phenotype, characterized by focal and atypical absence seizures, often preceded by febrile seizures, and age-dependent EEG changes, can be recognized in most patients with MWS.

SCN1A genetic test for Dravet Syndrome (Severe Myoclonic Epilepsy of Infancy and its clinical subtypes) for the use in the diagnosis, prognosis, treatment and management of Dravet Syndrome

Classic Dravet syndrome is also termed severe myoclonic epilepsy of infancy (SMEI). There are subtle phenotypic variants of Dravet which may have all the features of the syndrome except one, such as without myoclonic seizures, onset in the second year or without generalized spike and wave on EEG. These have been termed borderline variants of SMEI. Rather than ascribing multiple different names to marginally different phenotypes, the term Dravet syndrome is now preferred to describe the group of severe infantile onset epilepsies (OMIM #607208, #182389, #604403) associated with mutations in SCN1A (OMIM *182389). SCN1A-related seizure disorders can be inherited in an autosomal dominant manner but most are due to de novo mutations. SCN1A testing can be done through bi-directional DNA sequencing and multiplex ligation-dependent probe amplification (MLPA) for: 1) individuals with electroclinical phenotype of Dravet Syndrome or clinical sub-types – several seizure types in one individual with onset in infancy, refractory to medication and with generalised spike and wave on EEG, or 2) infants less than 1 year old with 2 or more prolonged hemiclonic febrile seizures in early infancy. Disclaimer: This summary is based on a UK Genetic Testing Network (UKGTN) approved Gene Dossier application.

Familial focal epilepsy with variable foci mapped to chromosome 22q12: Expansion of the phenotypic spectrum

We aimed to refine the phenotypic spectrum and map the causative gene in two families with familial focal epilepsy with variable foci (FFEVF). A new five-generation Australian FFEVF family (A) underwent electroclinical phenotyping, and the original four-generation Australian FFEVF family (B) (Ann Neurol, 44, 1998, 890) was re-analyzed, including new affected individuals. Mapping studies examined segregation at the chromosome 22q12 FFEVF region. In family B, the original whole genome microsatellite data was reviewed. Five subjects in family A and 10 in family B had FFEVF with predominantly awake attacks and active EEG studies with a different phenotypic picture from other families. In family B, reanalysis excluded the tentative 2q locus reported. Both families mapped to chromosome 22q12. Our results confirm chromosome 22q12 as the solitary locus for FFEVF. Both families show a subtly different phenotype to other published families extending the clinical spectrum of FFEVF.

Type II focal cortical dysplasia: Electroclinical phenotype and surgical outcome related to imaging

Type II focal cortical dysplasia (TTFCD), a highly epileptogenic lesion with severe epilepsy curable by surgery, is missed by magnetic resonance imaging (MRI) in about one third of cases. Little is known about the electroclinical presentation in these MRI-negative patients and a poor surgical outcome is frequently reported. We compared the clinical and neurophysiologic features in MRI-negative and MRI-positive cases in order to better identify candidates for surgery. Among 62 consecutive TTFCD patients (38 male, 24 female; 7-52 years old; 22 children) operated for intractable epilepsy, 25 (40%) presented negative MRI findings. We compared the history of epilepsy; the type, frequency, and distribution of seizures; neurologic examination cognitive and psychiatric impairment; interictal-ictal electroencephalography (EEG) and stereo-EEG (SEEG) data, fluorodeoxyglucose positron emission tomography (FDG-PET) data, neuropathologic findings; and surgical outcome in the MRI-negative and the MRI-positive groups. Severe partial epilepsy beginning in childhood, high seizure frequency including status epilepticus, stereotyped seizures suggestive of precise brain localization, extratemporal location and functional area involvement were characteristic and similarly found in both groups. On EEG, pseudorhythmic activity was found in about 40% of patients in each group. SEEG recordings demonstrated the typical pattern characterizing TTFCD in both groups. FDG-PET had a localization value in 84% of the MRI-negative cases and helped to delineate the dysplastic cortex in 65% of the MRI-positive cases. The combination of imaging and neurophysiologic data allowed us to perform safe and restricted resections, limited to a single gyrus in more than half of all cases. In addition, we were able to avoid invasive monitoring in most MRI-positive cases and even in some selected MRI-negative cases. The proportion of patients with a favorable surgical outcome was comparable in both groups (88% in MRI-negative and 94% in MRI-positive cases). The main difference between the groups was a significantly higher frequency of sleep-related epilepsy in the MRI-negative group (p = 0.028). This phenotypic characteristic provides a new argument for TTFCD in MRI-negative extratemporal epilepsy. These results lead us to consider that children or adult patients in whom electroclinical data suggest TTFCD, are highly suitable for surgery, especially for cryptogenic sleep-related epilepsy.

KCNQ2 encephalopathy: Emerging phenotype of a neonatal epileptic encephalopathy

KCNQ2 and KCNQ3 mutations are known to be responsible for benign familial neonatal seizures (BFNS). A few reports on patients with a KCNQ2 mutation with a more severe outcome exist, but a definite relationship has not been established. In this study we investigated whether KCNQ2/3 mutations are a frequent cause of epileptic encephalopathies with an early onset and whether a recognizable phenotype exists. We analyzed 80 patients with unexplained neonatal or early-infantile seizures and associated psychomotor retardation for KCNQ2 and KCNQ3 mutations. Clinical and imaging data were reviewed in detail. We found 7 different heterozygous KCNQ2 mutations in 8 patients (8/80; 10%); 6 mutations arose de novo. One parent with a milder phenotype was mosaic for the mutation. No KCNQ3 mutations were found. The 8 patients had onset of intractable seizures in the first week of life with a prominent tonic component. Seizures generally resolved by age 3 years but the children had profound, or less frequently severe, intellectual disability with motor impairment. Electroencephalography (EEG) at onset showed a burst-suppression pattern or multifocal epileptiform activity. Early magnetic resonance imaging (MRI) of the brain showed characteristic hyperintensities in the basal ganglia and thalamus that later resolved. KCNQ2 mutations are found in a substantial proportion of patients with a neonatal epileptic encephalopathy with a potentially recognizable electroclinical and radiological phenotype. This suggests that KCNQ2 screening should be included in the diagnostic workup of refractory neonatal seizures of unknown origin.

The three stages of epilepsy in patients with CDKL5 mutations

Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene are responsible for a severe encephalopathy with early epilepsy. So far, the electroclinical phenotype remains largely unknown and no clear genotype-phenotype correlations have been established. To characterize the epilepsy associated with CDKL5 mutations and to look for a relationship between the genotype and the course of epilepsy. We retrospectively analyzed the electroclinical phenotypes of 12 patients aged from 2.5 to 19 years diagnosed with pathogenic CDKL5 mutations and one patient with a novel intronic sequence variation of uncertain pathogenicity and examined whether the severity of the epilepsy was linked to the type and location of mutations. The epilepsy course reveals three successive stages: (Stage I) early epilepsy (onset 1-10 weeks) with normal interictal electroencephalogram (EEG) (10/13) despite frequent convulsive seizures; (Stage II) epileptic encephalopathy with infantile spasms (8/8) and hypsarrhythmia (8/8). At the age of evaluation, seven patients were seizure free and six had developed refractory epilepsy (stage III) with tonic seizures and myoclonia (5/6). Interestingly, the patients carrying a CDKL5 mutations causing a truncation of the catalytic domain tended to develop a more frequent refractory epilepsy than patients with mutations located downstream (4/6, 66.6% versus 1/6, 16%) although, these trends are not yet significant. Our data contribute to a better definition of the epileptic phenotype in CDKL5 mutations, and might give some clues to a potential relationship between the phenotype and the genotype in these patients.

Temporal lobe epilepsy and GEFS+ phenotypes associated with SCN1B mutations

SCN1B, the gene encoding the sodium channel beta 1 subunit, was the first gene identified for generalized epilepsy with febrile seizures plus (GEFS+). Only three families have been published with SCN1B mutations. Here, we present four new families with SCN1B mutations and characterize the associated phenotypes. Analysis of SCN1B was performed on 402 individuals with various epilepsy syndromes. Four probands with missense mutations were identified. Detailed electroclinical phenotyping was performed on all available affected family members including quantitative MR imaging in those with temporal lobe epilepsy (TLE). Two new families with the original C121W SCN1B mutation were identified; novel mutations R85C and R85H were each found in one family. The following phenotypes occurred in the six families with SCN1B missense mutations: 22 febrile seizures, 20 febrile seizures plus, five TLE, three other GEFS+ phenotypes, two unclassified and ten unaffected individuals. All individuals with confirmed TLE had the C121W mutation; two underwent temporal lobectomy (one with hippocampal sclerosis and one without) and both are seizure free. We confirm the role of SCN1B in GEFS+ and show that the GEFS+ spectrum may include TLE alone. TLE with an SCN1B mutation is not a contraindication to epilepsy surgery.