Ndnf Interneuron Excitability Is Spared in a Mouse Model of Dravet Syndrome

Dravet syndrome (DS) is a neurodevelopmental disorder characterized by epilepsy, developmental delay/intellectual disability, and features of autism spectrum disorder, caused by heterozygous loss-of-function variants in SCN1A encoding the voltage-gated sodium channel α subunit Nav1.1. The dominant model of DS pathogenesis is the "interneuron hypothesis," whereby GABAergic interneurons (INs) express and preferentially rely on Nav1.1-containing sodium channels for action potential (AP) generation. This has been shown for three of the major subclasses of cerebral cortex GABAergic INs: those expressing parvalbumin (PV), somatostatin, and vasoactive intestinal peptide. Here, we define the function of a fourth major subclass of INs expressing neuron-derived neurotrophic factor (Ndnf) in male and female DS (Scn1a+/-) mice. Patch-clamp electrophysiological recordings of Ndnf-INs in brain slices from Scn1a+/â mice and WT controls reveal normal intrinsic membrane properties, properties of AP generation and repetitive firing, and synaptic transmission across development. Immunohistochemistry shows that Nav1.1 is strongly expressed at the axon initial segment (AIS) of PV-expressing INs but is absent at the Ndnf-IN AIS. In vivo two-photon calcium imaging demonstrates that Ndnf-INs in Scn1a+/â mice are recruited similarly to WT controls during arousal. These results suggest that Ndnf-INs are the only major IN subclass that does not prominently rely on Nav1.1 for AP generation and thus retain their excitability in DS. The discovery of a major IN subclass with preserved function in the Scn1a+/â mouse model adds further complexity to the "interneuron hypothesis" and highlights the importance of considering cell-type heterogeneity when investigating mechanisms underlying neurodevelopmental disorders.

Microglia Mitigate Neuronal Activation in a Zebrafish Model of Dravet Syndrome

It has been known for a long time that epileptic seizures provoke brain neuroinflammation involving the activation of microglial cells. However, the role of these cells in this disease context and the consequences of their inflammatory activation on subsequent neuron network activity remain poorly understood so far. To fill this gap of knowledge and gain a better understanding of the role of microglia in the pathophysiology of epilepsy, we used an established zebrafish Dravet syndrome epilepsy model based on Scn1Lab sodium channel loss-of-function, combined with live microglia and neuronal Ca2+ imaging, local field potential (LFP) recording, and genetic microglia ablation. Data showed that microglial cells in scn1Lab-deficient larvae experiencing epileptiform seizures displayed morphological and biochemical changes characteristic of M1-like pro-inflammatory activation; i.e., reduced branching, amoeboid-like morphology, and marked increase in the number of microglia expressing pro-inflammatory cytokine Il1β. More importantly, LFP recording, Ca2+ imaging, and swimming behavior analysis showed that microglia-depleted scn1Lab-KD larvae displayed an increase in epileptiform seizure-like neuron activation when compared to that seen in scn1Lab-KD individuals with microglia. These findings strongly suggest that despite microglia activation and the synthesis of pro-inflammatory cytokines, these cells provide neuroprotective activities to epileptic neuronal networks, making these cells a promising therapeutic target in epilepsy.

Inhibitory synaptic transmission is impaired at higher extracellular Ca2+ concentrations in Scn1a+/- mouse model of Dravet syndrome

Dravet syndrome (DS) is an intractable form of childhood epilepsy that occurs in infancy. More than 80% of all patients have a heterozygous abnormality in the SCN1A gene, which encodes a subunit of Na+ channels in the brain. However, the detailed pathogenesis of DS remains unclear. This study investigated the synaptic pathogenesis of this disease in terms of excitatory/inhibitory balance using a mouse model of DS. We show that excitatory postsynaptic currents were similar between Scn1a knock-in neurons (Scn1a+/- neurons) and wild-type neurons, but inhibitory postsynaptic currents were significantly lower in Scn1a+/- neurons. Moreover, both the vesicular release probability and the number of inhibitory synapses were significantly lower in Scn1a+/- neurons compared with wild-type neurons. There was no proportional increase in inhibitory postsynaptic current amplitude in response to increased extracellular Ca2+ concentrations. Our study revealed that the number of inhibitory synapses is significantly reduced in Scn1a+/- neurons, while the sensitivity of inhibitory synapses to extracellular Ca2+ concentrations is markedly increased. These data suggest that Ca2+ tethering in inhibitory nerve terminals may be disturbed following the synaptic burst, likely leading to epileptic symptoms.

Somatostatin-expressing parafacial neurons are CO2/H+ sensitive and regulate baseline breathing

Glutamatergic neurons in the retrotrapezoid nucleus (RTN) function as respiratory chemoreceptors by regulating breathing in response to tissue CO2/H+. The RTN and greater parafacial region may also function as a chemosensing network composed of CO2/H+-sensitive excitatory and inhibitory synaptic interactions. In the context of disease, we showed that loss of inhibitory neural activity in a mouse model of Dravet syndrome disinhibited RTN chemoreceptors and destabilized breathing (Kuo et al., 2019). Despite this, contributions of parafacial inhibitory neurons to control of breathing are unknown, and synaptic properties of RTN neurons have not been characterized. Here, we show the parafacial region contains a limited diversity of inhibitory neurons including somatostatin (Sst)-, parvalbumin (Pvalb)-, and cholecystokinin (Cck)-expressing neurons. Of these, Sst-expressing interneurons appear uniquely inhibited by CO2/H+. We also show RTN chemoreceptors receive inhibitory input that is withdrawn in a CO2/H+-dependent manner, and chemogenetic suppression of Sst+ parafacial neurons, but not Pvalb+ or Cck+ neurons, increases baseline breathing. These results suggest Sst-expressing parafacial neurons contribute to RTN chemoreception and respiratory activity.

Impact of the COVID-19 lockdown on patients and families with Dravet syndrome

We explored the impact of coronavirus virus 2019 (COVID-19) pandemic on patients with Dravet syndrome (DS) and their family. With European patient advocacy groups (PAGs), we developed an online survey in 10 languages to question health status, behavior, personal protection, and health services before and after lockdown. Approximately 538 European PAG members received electronic invitations. Survey ran from April 14, to May 17, 2020, with 219 answers; median age 9 year 10 months. Protection against infection was highly used prior to COVID-19, but 88% added facemask-use according to pandemic recommendations. Only one patient was tested positive for COVID-19. Most had stable epilepsy during lockdown, and few families (4%) needed emergency care during lockdown. However, behavior disorder worsened in over one-third of patients, regardless of epilepsy changes. Half of appointments scheduled prior to lockdown were postponed; 12 patients (11%) had appointments fulfilled; and 39 (36%) had remote consultations. Responders welcomed remote consultations. Half of responders were unsatisfied with psychological remote support as only few (21 families) received this support. None of the five of patient in clinical trials stopped investigational treatment. Prior adoption of protective measures against general infection might have contributed to avoiding COVID-19 infections. Protocols for the favored remote contact ought to now be prepared.

The mechanics behind gait problems in patients with Dravet Syndrome

BACKGROUND

Dravet Syndrome (DS) is a developmental and epileptic encephalopathy starting in infancy and characterised by treatment resistant epilepsy with cognitive impairment and progressive motor dysfunction. Walking becomes markedly impaired with age, but the mechanical nature of gait problems remains unclear.

RESEARCH QUESTION

What are the kinetic strategies characterised in gait of patients with DS?

METHODS

This case-control study compared 41 patients with DS aged 5.2-26.1 years (19 female, 22 male) to 41 typically developing (TD) peers. Three dimensional gait analysis (VICON) was performed to obtain spatiotemporal parameters, kinematics and kinetics during barefoot, level walking at self-selected walking velocity. The sagittal plane support moment was analysed using Statistical Parametric Mapping (SPM). Three DS subgroups were identified based on differences in kinetic strategies characterised by the net internal knee joint moments and trunk lean. Kinematic and kinetic time profiles of the subgroups were compared to the TD group (SPM t-test). Clinical characteristics from physical examination and parental anamnesis were compared between DS (sub)groups using non-parametric tests (Kruskal-Wallis, Wilcoxon rank-sum, Fisher's exact).

RESULTS

Support moments in stance were significantly increased in the DS group compared to TD and strongly related to minimum knee flexion in midstance. Persistent internal knee extension moments during stance were detected in a subgroup of 27 % of the patients. A second subgroup of 34 % showed forward trunk lean and attained internal knee flexion moments. The remaining 39 % had neutral or backward trunk lean with internal knee flexion moments. Subgroups differed significantly in age and functional mobility.

SIGNIFICANCE

Inefficient kinetic patterns suggested that increased muscle effort was needed to control lower limb stability. Three distinct kinetic strategies that underly kinematic deviations were identified. Clinical evaluation of gait should pay attention to knee angles, trunk lean and support moments.

Developmental alterations in firing properties of hippocampal CA1 inhibitory and excitatory neurons in a mouse model of Dravet syndrome

Dravet syndrome (Dravet) is a rare, severe childhood-onset epilepsy, caused by heterozygous de novo mutations in the SCN1A gene, encoding for the alpha subunit of the voltage-gated sodium channel, Na_V1.1. The neuronal basis of Dravet is debated, with evidence favoring reduced function of inhibitory neurons, that might be transient, or enhanced activity of excitatory cells. Here, we utilized Dravet mice to trace developmental changes in the hippocampal CA1 circuit, examining the properties of CA1 horizontal stratum-oriens (SO) interneurons and pyramidal neurons, through the pre-epileptic, severe and stabilization stages of Dravet. Our data indicate that reduced function of SO interneurons persists from the pre-epileptic through the stabilization stages, with the greatest functional impairment observed during the severe stage. In contrast, opposing changes were detected in CA1 excitatory neurons, with a transient increase in their excitability during the pre-epileptic stage, followed by reduced excitability at the severe stage. Interestingly, alterations in the function of both inhibitory and excitatory neurons were more pronounced when the firing was evoked by synaptic stimulation, implying that loss of function of Na_V1.1 may also affect somatodendritic functions. These results suggest a complex pathophysiological mechanism and indicate that the developmental trajectory of this disease is governed by reciprocal functional changes in both excitatory and inhibitory neurons.

Abnormal brain gamma oscillations in response to auditory stimulation in Dravet syndrome

OBJECTIVE

To evaluate the capability of children with Dravet syndrome to generate brain γ-oscillatory activity in response to auditory steady-state stimulation.

METHODS

Fifty-one subjects were included: 13 with Dravet syndrome with SCN1A gene alterations, 26 with non-Dravet epilepsies and 12 healthy controls. Responses to auditory steady-state stimulation elicited with a chirp-modulated tone between 1 and 120 Hz were collected in subjects and compared across groups.

RESULTS

Subjects with Dravet syndrome showed weak or no responses in the 1-120 Hz frequency range. Healthy controls showed oscillatory responses following the frequency of the modulation that were maximal in the low (30-70 Hz) and high (80-120) γ-ranges both, in the power and inter-trial coherence estimates. Non-Dravet epileptic children showed differences in the auditory responses when compared with the healthy controls but were able to generate oscillatory evoked activities following the frequency-varying stimulation.

CONCLUSIONS

The ability to generate brain γ-oscillatory activity of children with Dravet in response to a chirp-modulated auditory stimulus is highly impaired, is not due to epilepsy and is consistent with the Nav1.1 channel dysfunction affecting interneuron activity seen in Dravet mouse models.

SIGNIFICANCE

The reported deficits in the brain oscillatory activity evoked by chirp modulated tones in children with Dravet is compatible with Dravet syndrome disease mechanisms and constitutes a potential biomarker for future disease-modifying interventions.

Benign spasms of infancy: a mimicker of infantile epileptic disorders

Benign spasms of infancy (BSI), previously described as benign non-epileptic infantile spasms or benign myoclonus of early infancy, are non-epileptic movements manifesting during the first year of life and spontaneously resolving in the second year of life. BSI are characterized by spasms typically lasting 1-2 seconds, involving, to varying degrees, the head, neck, trunk, shoulders and upper extremities. Ictal and interictal EEG recordings are normal. BSI are not associated with developmental regression and do not require treatment. Distinction between BSI and infantile epileptic disorders, such as epileptic spasms or myoclonic epilepsy of infancy, can be challenging given the clinical similarities. Moreover, interictal EEGs can be normal in all conditions. Epileptic spasms and myoclonic epilepsy require timely treatment to improve neurodevelopmental outcomes. We describe a six-month-old infant presenting with spasm-like movements. His paroxysms as well as a positive family history for epileptic spasms were in keeping with a likely diagnosis of West syndrome. Surprisingly, ictal video-EEG did not reveal epileptiform activity, and suggested a diagnosis of BSI. We emphasize that ictal video-EEG is the gold standard for classification of infantile paroxysms as epileptic or non-epileptic, thereby avoiding over-treatment for BSI and facilitating timely targeted treatment of infantile epilepsies. [Published with video sequences].

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.

Vasoactive intestinal peptide-expressing interneurons are impaired in a mouse model of Dravet syndrome

Dravet Syndrome (DS) is a severe neurodevelopmental disorder caused by pathogenic loss of function variants in the gene SCN1A which encodes the voltage gated sodium (Na+) channel subunit Nav1.1. GABAergic interneurons expressing parvalbumin (PV-INs) and somatostatin (SST-INs) exhibit impaired excitability in DS (Scn1a+/-) mice. However, the function of a third major class of interneurons in DS - those expressing vasoactive intestinal peptide (VIP-IN) -is unknown. We recorded VIP-INs in brain slices from Scn1a+/-mice and wild-type littermate controls and found prominent impairment of irregular spiking (IS), but not continuous adapting (CA) VIP-INs, in Scn1a+/- mice. Application of the Nav1.1-specific toxin Hm1a rescued the observed deficits. The IS vs. CA firing pattern is determined by expression of KCNQ channels; IS VIP-INs switched to tonic firing with both pharmacologic blockade of M-current and muscarinic acetylcholine receptor activation. These results show that VIP-INs express Nav1.1 and are dysfunctional in DS, which may contribute to DS pathogenesis.

Disordered breathing in a mouse model of Dravet syndrome

Dravet syndrome (DS) is a form of epilepsy with a high incidence of sudden unexpected death in epilepsy (SUDEP). Respiratory failure is a leading cause of SUDEP, and DS patients' frequently exhibit disordered breathing. Despite this, mechanisms underlying respiratory dysfunction in DS are unknown. We found that mice expressing a DS-associated Scn1a missense mutation (A1783V) conditionally in inhibitory neurons (Slc32a1cre/+::Scn1aA1783V fl/+; defined as Scn1aΔE26) exhibit spontaneous seizures, die prematurely and present a respiratory phenotype including hypoventilation, apnea, and a diminished ventilatory response to CO2. At the cellular level in the retrotrapezoid nucleus (RTN), we found inhibitory neurons expressing the Scn1a A1783V variant are less excitable, whereas glutamatergic chemosensitive RTN neurons, which are a key source of the CO2/H+-dependent drive to breathe, are hyper-excitable in slices from Scn1aΔE26 mice. These results show loss of Scn1a function can disrupt respiratory control at the cellular and whole animal levels.

In vivo, in vitro and in silico correlations of four de novo SCN1A missense mutations

Mutations in the SCN1A gene, which encodes for the voltage-gated sodium channel Na_V1.1, cause Dravet syndrome, a severe developmental and epileptic encephalopathy. Genetic testing of this gene is recommended early in life. However, predicting the outcome of de novo missense SCN1A mutations is difficult, since milder epileptic syndromes may also be associated. In this study, we correlated clinical severity with functional in vitro electrophysiological testing of channel activity and bioinformatics prediction of damaging mutational effects. Three patients, bearing the mutations p.Gly177Ala, p.Ser259Arg and p.Glu1923Arg, showed frequent intractable seizures that had started early in life, with cognitive and behavioral deterioration, consistent with classical Dravet phenotypes. These mutations failed to produce measurable sodium currents in a mammalian expression system, indicating complete loss of channel function. A fourth patient, who harbored the mutation p.Met1267Ile, though presenting with seizures early in life, showed lower seizure burden and higher cognitive function, matching borderland Dravet phenotypes. In correlation with this, functional analysis demonstrated the presence of sodium currents, but with partial loss of function. In contrast, six bioinformatics tools for predicting mutational pathogenicity suggested similar impact for all mutations. Likewise, homology modeling of the secondary and tertiary structures failed to reveal misfolding. In conclusion, functional studies using patch clamp are suggested as a prognostic tool, whereby detectable currents imply milder phenotypes and absence of currents indicate an unfavorable prognosis. Future development of automated patch clamp systems will facilitate the inclusion of such functional testing as part of personalized patient diagnostic schemes.

Small changes in synaptic gain lead to seizure-like activity in neuronal network at criticality

Epilepsy is a neurological disorder characterised by spontaneous recurrent seizures. The mechanisms by which multiple molecular and cellular changes lead to seizures is not well understood. Here, we study cortical seizure generation by simulating the activity of neuron groups in a network using the laminar cortex model. We identified a clear boundary between low-amplitude, asynchronous activity and high-amplitude, rhythmic activity, around which small changes in excitatory synaptic gain led to strong oscillatory activity. Neuron groups only responded significantly to stimulation around the boundary. The consequences of biophysical changes induced by epilepsy-related SCN1A mutations were also examined. Marked reduction in neuronal inhibition, as caused by mutations underlying Dravet syndrome, invariably led to strong neuronal firing, whereas small reductions in inhibition could cause significant changes when the network was poised close to the boundary. The study highlights the critical role of network dynamics in seizure genesis.

De novo variants in GABRA2 and GABRA5 alter receptor function and contribute to early-onset epilepsy

GABAA receptors are ligand-gated anion channels that are important regulators of neuronal inhibition. Mutations in several genes encoding receptor subunits have been identified in patients with various types of epilepsy, ranging from mild febrile seizures to severe epileptic encephalopathy. Using whole-genome sequencing, we identified a novel de novo missense variant in GABRA5 (c.880G > C, p.V294L) in a patient with severe early-onset epilepsy and developmental delay. Targeted resequencing of 279 additional epilepsy patients identified 19 rare variants from nine GABAA receptor genes, including a novel de novo missense variant in GABRA2 (c.875C > A, p.T292K) and a recurrent missense variant in GABRB3 (c.902C > T, p.P301L). Patients with the GABRA2 and GABRB3 variants also presented with severe epilepsy and developmental delay. We evaluated the effects of the GABRA5, GABRA2 and GABRB3 missense variants on receptor function using whole-cell patch-clamp recordings from human embryonic kidney 293T cells expressing appropriate α, β and γ subunits. The GABRA5 p.V294L variant produced receptors that were 10-times more sensitive to GABA but had reduced maximal GABA-evoked current due to increased receptor desensitization. The GABRA2 p.T292K variant reduced channel expression and produced mutant channels that were tonically open, even in the absence of GABA. Receptors containing the GABRB3 p.P301L variant were less sensitive to GABA and produced less GABA-evoked current. These results provide the first functional evidence that de novo variants in the GABRA5 and GABRA2 genes contribute to early-onset epilepsy and developmental delay, and demonstrate that epilepsy can result from reduced neuronal inhibition via a wide range of alterations in GABAA receptor function.

Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review

Background

Autosomal dominant familial cortical myoclonic tremor and epilepsy (FCMTE) is characterized by distal tremulous myoclonus, generalized seizures, and signs of cortical reflex myoclonus. FCMTE has been described in over 100 pedigrees worldwide, under several different names and acronyms. Pathological changes have been located in the cerebellum. This systematic review discusses the clinical spectrum, treatment, pathophysiology, and genetic findings.

Methods

We carried out a PubMed search, using a combination of the following search terms: cortical tremor, myoclonus, epilepsy, benign course, adult onset, familial, and autosomal dominant; this resulted in a total of 77 studies (761 patients; 126 pedigrees) fulfilling the inclusion and exclusion criteria.

Results

Phenotypic differences across pedigrees exist, possibly related to underlying genetic differences. A "benign" phenotype has been described in several Japanese families and pedigrees linked to 8q (FCMTE1). French patients (5p linkage; FCMTE3) exhibit more severe progression, and in Japanese/Chinese pedigrees (with unknown linkage) anticipation has been suggested. Preferred treatment is with valproate (mind teratogenicity), levetiracetam, and/or clonazepam. Several genes have been identified, which differ in potential pathogenicity.

Discussion

Based on the core features (above), the syndrome can be considered a distinct clinical entity. Clinical features may also include proximal myoclonus and mild progression with aging. Valproate or levetiracetam, with or without clonazepam, reduces symptoms. FCMTE is a heterogeneous disorder, and likely to include a variety of different conditions with mutations of different genes. Distinct phenotypic traits might reflect different genetic mutations. Genes involved in Purkinje cell outgrowth or those encoding for ion channels or neurotransmitters seem good candidate genes.

[Myoclonus as a movement disorder]

Myoclonus is often a diagnostic and therapeutic challenge due to its broad phenomenological variability and limited therapeutic options. This article gives a short survey and characterizes in detail two common types of myoclonus, cortical myoclonus and reticular reflex myoclonus. Clinical testing and electrophysiological investigations provide relevant local diagnostic indications for the generating structure(s). Such indications would influence not only the strategies of neuroimaging and laboratory investigations aimed at clarifying the underlying cause but also the selection of drugs to suppress myoclonus.

Age-related "Sleep/nocturnal" tonic and tonic clonic seizure clusters are underdiagnosed in patients with Dravet Syndrome

OBJECTIVES

To describe the semiology and EEG characteristics of the age-related pattern of sleep/nocturnal (S/N) seizures in patients with Dravet Syndrome (DS).

METHODS

We retrospectively analysed the clinical and EEG data of DS patients followed at our reference centre for Rare Epilepsies. We included patients aged two years and older who fulfilled clinical and EEG criteria of DS (ILAE 1989). Genetic testing for SCN1A was done in all, followed by PCDH19 if this was negative. Patients showing a genetic abnormality in PCDH19 were excluded. Of 73 DS patients followed at our centre, 26 (15 males and 11 females), called the S/N group, experienced a switch in the circadian rhythm of seizures, from mainly awake/diurnal to mainly S/N seizures. We retrospectively analysed their clinical, EEG and genetic data. We have compared them to a second group of 7 patients (4 males and 3 females), aged more than 11years, the non-S/N group, who did not develop S/N seizures.

RESULTS

We observed a pattern of S/N seizures concomitant with a decrease of awake seizures between 4 and 11years (median 6years 6months). S/N seizures were brief but often occurred in clusters of 2-15 per night. Seizures were mostly focal (26) with frontal-central onset (25) and tonic or tonic-vibratory in semiology. S/N seizure clusters were difficult to control despite many AEDs trials. Benzodiazepines reduced seizure recurrence within a cluster in some patients. While no significant differences were found between groups regarding clinical features, the presence of frontal and central anomalies on wake and sleep EEG was significantly associated with the presence of the S/N pattern.

CONCLUSIONS

Patients with DS often develop a characteristic clinical and EEG pattern with S/N tonic and tonic clonic seizures that is often underdiagnosed. Seizure semiology and EEG pattern differ from LGS but may worsen the quality of sleep of such patients and their families. The possible role of this pattern in SUDEP occurring mainly during sleep and at the same age should be further explored. Current AEDs have limited efficacy and specific drug trials should be proposed.

Impaired intracortical inhibition demonstrated in vivo in people with Dravet syndrome

OBJECTIVE

Dravet syndrome is a rare neurodevelopmental disorder characterized by seizures and other neurologic problems. SCN1A mutations account for ∼80% of cases. Animal studies have implicated mutation-related dysregulated cortical inhibitory networks in its pathophysiology. We investigated such networks in people with the condition.

METHODS

Transcranial magnetic stimulation using single and paired pulse paradigms was applied to people with Dravet syndrome and to 2 control groups to study motor cortex excitability.

RESULTS

Short interval intracortical inhibition (SICI), which measures GABAergic inhibitory network behavior, was undetectable in Dravet syndrome, but detectable in all controls. Other paradigms, including those testing excitatory networks, showed no difference between Dravet and control groups.

CONCLUSIONS

There were marked differences in inhibitory networks, detected using SICI paradigms, while other inhibitory and excitatory paradigms yielded normal results. These human data showing reduced GABAergic inhibition in vivo in people with Dravet syndrome support established animal models.

Infantile, Childhood, and Adolescent Epilepsies

PURPOSE OF REVIEW

Infantile, childhood, and adolescent epilepsies comprise a diverse group of entities. Careful characterization of epilepsy into a specific electroclinical syndrome or etiology assists greatly in understanding both the natural history of the seizure disorder (pharmacoresistant versus pharmacoresponsive and self-limited versus lifelong) and the best therapeutic options for the child.

RECENT FINDINGS

Tremendous growth has been seen in the understanding of both genetic factors predisposing to epilepsy and neuroimaging techniques. Additionally, a number of studies have focused on the efficacy of certain therapies in specific syndromes or etiologies.

SUMMARY

This article reviews both common epilepsy syndromes (including benign focal epilepsy of childhood, absence epilepsy, and juvenile myoclonic epilepsy) and the rarer syndromes with associated management implications (eg, Dravet syndrome, progressive myoclonic epilepsy, and mitochondrial disorders) and addresses genetic and metabolic investigations.

Gray Matter Loss and Related Functional Connectivity Alterations in A Chinese Family With Benign Adult Familial Myoclonic Epilepsy

Benign adult familial myoclonic epilepsy (BAFME) is a non-progressive monogenic epilepsy syndrome. So far, the structural and functional brain reorganizations in BAFME remain uncharacterized. This study aims to investigate gray matter atrophy and related functional connectivity alterations in patients with BAFME using magnetic resonance imaging (MRI).Eleven BAFME patients from a Chinese pedigree and 15 matched healthy controls were enrolled in the study. Optimized voxel-based morphometric and resting-state functional MRI approaches were performed to measure gray matter atrophy and related functional connectivity, respectively. The Trail-Making Test-part A and part B, Digit Symbol Test (DST), and Verbal Fluency Test (VFT) were carried out to evaluate attention and executive functions.The BAFME patients exhibited significant gray matter loss in the right hippocampus, right temporal pole, left orbitofrontal cortex, and left dorsolateral prefrontal cortex. With these regions selected as seeds, the voxel-wise functional connectivity analysis revealed that the right hippocampus showed significantly enhanced connectivity with the right inferior parietal lobule, bilateral middle cingulate cortex, left precuneus, and left precentral gyrus. Moreover, the BAFME patients showed significant lower scores in DST and VFT tests compared with the healthy controls. The gray matter densities of the right hippocampus, right temporal pole, and left orbitofrontal cortex were significantly positively correlated with the DST scores. In addition, the gray matter density of the right temporal pole was significantly positively correlated with the VFT scores, and the gray matter density of the right hippocampus was significantly negatively correlated with the duration of illness in the patients.The current study demonstrates gray matter loss and related functional connectivity alterations in the BAFME patients, perhaps underlying deficits in attention and executive functions in the BAFME.

The Epileptic Encephalopathies of Infancy and Childhood

The epileptic encephalopathies comprise a group of devastating seizure syndromes which begin in infancy and early childhood and usually result in intractable epilepsy. While some syndromes are relatively easily diagnosed early in their course, others take time to evolve, hampering an early, confident diagnosis. Epileptic encephalopathies are associated with slowing of cognitive function and evolution of severe behavioral disorders, which are often more distressing to families than the epilepsy. While an underlying etiology may explain some of this co-morbidity, many children have no identifiable etiology found for their seizures. In these “idiopathic” cases, recurrent subtle seizures, frequent epileptiform discharge and non-convulsive status epilepticus probably all play a role in deterioration of cognitive function and evolution of behavior disorders. This paper will review the most common epileptic encephalopathy syndromes, discuss the cognitive and behavioral co-morbidities and review current therapeutic options.

The α2B-adrenergic receptor is mutant in cortical myoclonus and epilepsy

OBJECTIVE

Autosomal dominant cortical myoclonus and epilepsy (ADCME) is characterized by distal, fairly rhythmic myoclonus and epilepsy with variable severity. We have previously mapped the disease locus on chromosome 2p11.1-q12.2 by genome-wide linkage analysis. Additional pedigrees affected by similar forms of epilepsy have been associated with chromosomes 8q, 5p, and 3q, but none of the causing genes has been identified. We aim to identify the mutant gene responsible for this form of epilepsy.

METHODS

Genes included in the ADCME critical region were directly sequenced. Coimmunoprecipitation, immunofluorescent, and electrophysiologic approaches to transfected human cells have been utilized for testing the functional significance of the identified mutation.

RESULTS

Here we show that mutation in the α2 -adrenergic receptor subtype B (α2B -AR) is associated with ADCME by identifying a novel in-frame insertion/deletion in 2 Italian families. The mutation alters several conserved residues of the third intracellular loop, hampering neither the α2B -AR plasma membrane localization nor the arrestin-mediated internalization capacity, but altering the binding with the scaffolding protein spinophilin upon neurotransmitter activation. Spinophilin, in turn, regulates interaction of G protein coupled receptors with regulator of G protein signaling proteins. Accordingly, the mutant α2B -AR increases the epinephrine-stimulated calcium signaling.

INTERPRETATION

The identified mutation is responsible for ADCME, as the loss of α2B -AR/spinophilin interaction causes a gain of function effect. This work implicates for the first time the α-adrenergic system in human epilepsy and opens new ways of understanding the molecular pathway of epileptogenesis, widening the spectrum of possible therapeutic targets.

[Perioral myoclonia syndrome with absences: about 2 cases]

Perioral myoclonia with absences (POMA) was first described in 1994 by CP Panayotopoulos who identified 6 cases that did not fit with the classical syndrome of absence epilepsy in children and whose predominant symptom during the absence seizure was the occurrence of myoclonia of perioral muscles. The POMA belongs to the group of generalized idiopathic epilepsies. It begins in childhood and there is a female predominance. It may be accompanied by tonic-clonic generalized seizures as well as absence status epilepticus. It has the EEG characteristics of typical absence seizures and therefore remains currently considered as such. The clinical manifestations of POMA are often misdiagnosed as focal motor seizures. This syndrome can be pharmacoresistant and is not likely to regress spontaneously. We present two clinical observations of perioral myoclonia with absences. The first case illustrates the typical electro-clinical features of this syndrome while the second illustrates its pharmacoresistance.

[Diagnosis and treatment of epilepsy and narcolepsy comorbid]

OBJECTIVE

To analyze the clinical diagnosis and treatment process of narcolepsy and epilepsy co-existence, and thereby to improve awareness of such cases.

METHOD

The clinical manifestations of 2 cases were observed, and video-electroencephalogram (VEEG), multiple sleep latency tests (MSLT) were performed. Hypocretin 1 level in cerebrospinal fluid was examined in one case.

RESULT

The onset of disease of case one was started with epilepsy with myoclonic seizure. After half a year, catalepsy induced by emotion especially laughing and excessive daytime sleepiness appeared. MSLT was positive and hypocretin 1 level decreased. Narcolepsy-cataplexy was definitely diagnosed in this case. Valproate was given and seizure was controlled completely, but the excessive daytime sleepiness was aggravated. Combination of valproate, methylphenidate and clomipramine treatment improved the symptoms of narcolepsy and the patient was still free of epileptic seizures. The onset symptoms of case 2 were catalepsy and excessive daytime sleepiness. MSLT was positive. The treatment was ineffective because of bad compliance. After 2 years, episodes of impairment of consciousness with automatism occurred. VEEG showed slow waves and spikes in right temporal area. Complex partial seizure was determined. Oxcarbazepine was used and then the patients became seizures free, but the symptoms of narcolepsy were still obvious.

CONCLUSION

Comorbidity of narcolepsy and epilepsy is a rare phenomenon. Clinical symptoms, predisposing factor, VEEG and MSLT can help diagnosis and differential diagnosis. The antiepileptic drugs might aggravate drowsiness. Based on therapy of epilepsy by using antiepileptic drugs, low dosage of central nervous system stimulants might improve the drowsiness and catalepsy symptoms of narcolepsy.

Treadmill exercise protects against pentylenetetrazol-induced seizures and oxidative stress after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of acquired epilepsy, and significant resources are required to develop a better understanding of the pathologic mechanism as targets for potential therapies. Thus, we decided to investigate whether physical exercise after fluid percussion injury (FPI) protects from oxidative and neurochemical alterations as well as from behavioral electroencephalographic (EEG) seizures induced by subeffective convulsive doses of pentylenetetrazol (PTZ; 35 mg/kg). Behavioral and EEG recordings revealed that treadmill physical training increased latency to first clonic and tonic-clonic seizures, attenuated the duration of generalized seizures, and protected against the increase of PTZ-induced Racine scale 5 weeks after neuronal injury. EEG recordings also revealed that physical exercise prevented PTZ-induced amplitude increase in TBI animals. Neurochemical analysis showed that exercise training increased glutathione/oxidized glutathione ratio and glutathione levels per se. Exercise training was also effective against alterations in the redox status, herein characterized by lipid peroxidation (thiobarbituric acid reactive substances), protein carbonyl increase, as well as the inhibition of superoxide dismutase and Na⁺,K⁺-ATPase activities after FPI. On the other hand, histologic analysis with hematoxylin and eosin revealed that FPI induced moderate neuronal damage in cerebral cortex 4 weeks after injury and that physical exercise did not protect against neuronal injury. These data suggest that the ability of physical exercise to reduce FPI-induced seizures is not related to its protection against neuronal damage; however, the effective protection of selected targets, such as Na⁺/K⁺-ATPase elicited by physical exercise, may represent a new line of treatment for post-traumatic seizure susceptibility.

QT and P wave dispersion and heart rate variability in patients with Dravet syndrome

SCN1A mutations are found in up to 80 % of patients with Dravet syndrome (DS), and the sudden unexpected death in epilepsy (SUDEP) rate is higher in DS than in most forms of severe epilepsy. The aim of this study is to examine the autonomic cardiac function and the risk of arrhythmia in DS patients by evaluating QT and P wave dispersion and heart rate variability (HRV) using standard electrocardiography (ECG) and 24-h ECG. The study group consisted of 15 patients (9 boys and 6 girls aged 3.5-17 years) who were genetically diagnosed with DS. The control group comprised 20 healthy subjects, 13 boys and 7 girls aged 4-17 years. P wave dispersion (44.6 ± 3.5 ms), QT dispersion (58.8 ± 7.5 ms) and QTc dispersion (70.8 ± 7.4 ms) were significantly higher in DS patients as compared to the control group (p < 0.001 for all values). However, there was no significant difference in PR, QT or QTc length between the groups. 24-h Holter ECG showed that all HRV parameters were significantly lower in patients with DS. The decreased HRV and increased P wave and QT dispersion seen in DS patients are important signs of autonomic dysfunction with increased adrenergic tone. To determine whether autonomic dysfunction is correlated with SUDEP in DS, long-term electrocardiographic monitoring and wider prospective studies are necessary.

[Cognitive development in Dravet's syndrome as a model of epileptic encephalopathy]

Cognitive development in Dravet's syndrome is accompanied by a slowing or stagnation of the cognitive abilities during childhood. The fact that the syndrome is classified within the group of epileptic encephalopathies suggests that the epileptiform activity plays an important role in the genesis of the cognitive disorders. In this review it is shown that the epileptic phenotype and the critical and intercritical activity do not, by themselves, explain the cognitive development in children with Dravet's syndrome. Substantial changes in the treatment, with impact on cognitive development, will probably come with therapies that act by directly modifying the pathophysiology of the syndrome rather than its consequences.

[Simple febrile seizure, complex seizure, generalized epilepsy with febrile seizure plus, FIRES and new syndromes]

Febrile seizures are the most common seizures in childhood. They have been observed in 2-5% of children before the age of 5, but in some populations this figure may increase to 15%. It is a common cause of pediatric hospital admissions and cause of anxiety for parents. Febrile seizures could be the first manifestation of epilepsy. About 13% of epileptic patients have a history of febrile seizure, and 30% have had recurrent febrile seizures. Their phenotypic characteristics allow, in the majority of cases, a classification of the seizure, an elaboration of a prognosis and to assume a specific therapeutic attitude. It is possible to describe a spectrum according to their severity, from the benign simple seizure to the more complex, febrile seizure plus, Dravet'syndrome, and FIRES. During the past decade, molecular genetic studies have contributed to the identification of genetic factors involved in febrile seizure and related disorders, making the necessity of a careful follow up of these patients in order to detect risk factors earlier. We have reviewed the medical literature to update current knowledge of febrile seizures, their prognosis and their relation to new epileptic syndromes.

[The clinical and electroencephalographic characteristics of early myoclonic encephalopathy]

OBJECTIVE

To investigate the clinical and electroencephalographic (EEG) characteristics, therapeutic response and long-term prognosis of early myoclonic encephalopathy.

METHOD

The clinical and EEG data of three patients with early myoclonic encephalopathy were analyzed. These patients were admitted to our hospital between September 2008 and January 2012. The patients were followed up for therapeutic response and long-term prognosis.

RESULT

The age of onset was from 2 to 23 days after birth. All patients had the onset of erratic or fragmentary myoclonus. Two patients had frequent simple focal seizures. One patient had tonic spasms when he was 3 months old. The EEG characteristic of all patients was repetitive suppression-burst pattern. The suppression-burst pattern was characterized by paroxysmal short bursts and long periods of suppression. The EEG paroxysms of one patient was asynchronous over both hemispheres. There is no effective therapy for early myoclonic encephalopathy. A patient died before two years of age. Two patients had severe partial epilepsy and showed very severe retardation.

CONCLUSION

Early myoclonic encephalopathy usually starts in the first month of life. Erratic myoclonus appears first. Myoclonus is the principal features of early myoclonic encephalopathy. Frequent focal seizures occur shortly after erratic myoclonus. Tonic epileptic spasms may develop within 3 - 5 months. The suppression-burst pattern is EEG characteristic. There is no effective therapy for early myoclonic encephalopathy and the prognosis is poor.

Benign myoclonic epilepsy in infancy with preceding afebrile generalized tonic-clonic seizures in Japan

Benign myoclonic epilepsy in infancy (BMEI) is the youngest form of idiopathic generalized epilepsy, characterized by myoclonic seizures (MS) in the first three years of life in otherwise normal infants, and the lack of other seizure types except for rare simple febrile seizures. Although afebrile generalized tonic-clonic seizures (GTCS) have been described to develop later in the clinical course of BMEI, mostly during adolescence, an association with GTCS in the early stage of BMEI has never been recognized. We herein report seven children who satisfied the criteria of BMEI except for the recurrence of GTCS before the onset of MS. The age of onset and ictal video-polygraphic features of MS, as well as the long-term seizure and developmental outcome in these children were similar to those of children with typical BMEI. Furthermore, these GTCS mostly disappeared within several months and were replaced by MS. Our study indicates that these children may constitute a BMEI subgroup, expanding the spectrum of BMEI.

Dravet syndrome: the main issues

Dravet syndrome (DS) is a severe form of infantile onset epilepsy characterized by multiple seizure types, prolonged convulsive seizures and frequent episodes of status epilepticus. Seizures precipitated by fever are a main characteristic. Affected children exhibit normal early development. Cognitive impairment, behavioral disturbances with hyperactivity and sometimes autistic traits occur after seizure onset. Seizures persist into adulthood but become less frequent. In about 85% of patients, a mutation of the SCN1A gene is present. DS fully illustrates the concept of epileptic encephalopathy. However, it is difficult to determine the causative role of the underlying sodium channel dysfunction and that of the consequent seizures in influencing cognitive outcome. An overwhelmingly high number of SCN1A mutations have been associated with DS. Intragenic or whole gene deletions, duplications and amplifications are additional rare molecular mechanisms. Most mutations are de novo, but familial mutations also occur. Somatic mosaic mutations should be considered when estimating the recurrence. MRI imaging is usually normal, and no neuropathologic signature of the condition seems to exist. In heterozygous Scn1a+/- mice, GABAergic interneurons exhibit substantially reduced sodium current density with reduced ability for sustained action potential firing. GABAergic output is reduced and excitability of downstream synaptic targets increased. Stiripentol was effective in combination with valproate and clobazam in two pivotal phase III trials. Phenytoin, carbamazepine, and lamotrigine can worsen seizures and should be avoided. Prospective studies will clarify to what extent earlier diagnosis and efforts at seizure control with the most appropriate drug combinations will reduce clinical deterioration.

[Clinical and electroencephalographic characteristics of Jeavons syndrome]

OBJECTIVE

The study was designed to examine the clinical and electroencephalographic characteristics of children with Jeavons syndrome.

METHOD

Video-electroencephalography (VEEG) monitoring was carried out in 9 patients with Jeavons syndrome. The clinical and electroencephalographic characteristics, treatment and prognoses were analyzed.

RESULT

Of the 9 patients, 8 were female, and 1 was male. The onset age of children with eyelid myoclonia (EM) was from 3 to 9 years old. It was obtained through the chief complaint, prosecution or VEEG monitoring. Three cases were misdiagnosed and 2 cases were overlooked initially. Seven out of 9 patients had generalized tonic clonic seizures (GTCS) during the course of disease, of whom 5 experienced only one episode. GTCS was the cause for the first visits to hospital in 5 patients. Since the clinical manifestations of EM with or without absence were often slight, VEEG monitoring with eye closure and intermittent photic stimulation tests helped to induce discharges and seizures. Eye closure was more potent than intermittent photic stimulation as a triggering factor. Ictal EEG showed 3 - 6 Hz generalized spike and waves and polyspikes burst. The main treatment option was valproate monotherapy (6 cases) or combined with other antiepileptic drugs (1 case). Levetiracetam, lamotrigine and topiramate were also used in patients and effective to some degree. Two patients lost follow up. The age of 7 patients at follow-up ranged from 9 y to 15 y. Seizures were controlled in 1 case, suspiciously controlled in 1 case, decreased in frequency in 4 cases and were still frequent in 1 case. During follow-up, normal intelligence was found in the former 2 cases, difficult learning in 2 cases, and slightly intellectual impairment in 2 cases.

CONCLUSION

Jeavons syndrome is one of the idiopathic generalized epilepsies characterized by EM with or without absence. The age of seizure onset might be difficult to be exactly established, as EM was often misinterpreted and overlooked initially. Clinical history combined with VEEG monitoring with eye closure and intermittent photic stimulation tests could diagnose this disease. Valproate and other new antiepileptic drugs were effective for this disease. Jeavons syndrome is a lifelong disorder. Seizures sometimes could be well controlled. When seizures were resistant to treatment, cognitive and intellectual impairment might occur.

Dravet syndrome--considerable delay in making the diagnosis

OBJECTIVES

To assess delay in diagnosis and clinical characteristics of Dravet syndrome based on the Dravet register at The National Centre for Epilepsy in Norway.

MATERIAL AND METHODS

Medical records of patients diagnosed with Dravet syndrome since 2007 were analysed.

RESULTS

Twenty-two patients were identified. In 15, genetic screening disclosed mutations/deletions in the SCN1A gene. Average time from seizure onset to diagnosis was 7.4 years. Mean age at seizure onset was 6.7 months, nine had hemiconvulsions and 13 had generalized tonic-clonic seizures. The seizures were precipitated by fever in 17, by external heating in three. During second year of life, multiple seizure types and cognitive and motoric stagnation occurred. No patients became seizure-free with antiepileptic drugs. The effect of vagal nerve stimulation was disappointing.

CONCLUSIONS

By making an early diagnosis, an extensive presurgical evaluation may be avoided, and the patient and their parents may be offered genetic guidance.

The classification and differential diagnosis of absence seizures with short-term video-EEG monitoring during childhood

Absence seizures are idiopathic epilepsies characterized by impairment of consciousness and generalized 2.5-4 Hz spike and slow wave discharges. This prospective study was performed to classify and define properties of subgroups of absence epilepsies. We included 31 patients, of whom seven were in the differential diagnosis group. On admission, absence epilepsy provisional diagnosis was considered in 16 patients clinically and in the other 15 patients based on routine EEG findings. Ictal EEGs were recorded by video-EEG monitoring in 23 of the patients (totally 202 ictal recordings). Patients were diagnosed as childhood absence epilepsy (n=8), juvenile absence epilepsy (n=10), juvenile myoclonic epilepsy (n=3), eyelid myoclonia with absences (n=2), and perioral myoclonia with absences (n=1). Neuroimaging, video-EEG monitoring and especially ictal recordings are important for classification of epilepsies in addition to history, physical examination and routine EEG findings. Video-EEG monitoring is required to classify, to make differential diagnosis and to determine the treatment plan and prognosis.

Genetic diagnosis of severe myoclonic epilepsy of infancy (Dravet syndrome) with SCN1A mutations in the Hong Kong Chinese patients

Epilepsy is a clinically and genetically heterogeneous group of disorders. The advent of molecular genetics brings unprecedented advancement in diagnostic molecular pathology and reduces over-reliance on traditional clinical classification. Severe myoclonic epilepsy of infancy or Dravet syndrome is a catastrophic infantile-onset epilepsy. We report two unrelated Hong Kong Chinese patients with this condition presenting with febrile seizures, epilepsy with different semiologies, psychomotor retardation, and recurrent status epilepticus. Two different mutations were characterised, viz NM_001165963.1: c.680T>G; NP_001159435.1: p.I227S and NM_001165963.1: c.3953T>G; NP_001159435.1: p.L1318R (novel). Genetic characterisation conveys a definitive diagnosis and is important from the perspective of selecting anti-epileptic drug therapy and genetic counselling.

[Electroclinical features of myoclonic-atonic epilepsy]

OBJECTIVE

To summarize the electroclinical characteristics of myoclonic atonic epilepsy (MAE) in children.

METHOD

The clinical data, video electroencephalogram (EEG) and simultaneous electromyography (EMG) of MAE patients were analyzed. The treatment and its effects were followed up.

RESULT

In 47 MAE patients, 25 had a history of febrile seizures (FS), 20 had a family history of FS or epilepsy. All patients had a normal development before the illness. The age of afebrile seizure onset was between 1.4 years to 5.8 years. The first seizure was generalized tonic-clonic seizure (GTCS) in 41 patients (87.2%). All patients had multiple seizure types, including 47 GTCS (97.9%), 34 myoclonic atonic seizures (72.3%), 47 myoclonic seizures (100%), 32 atonic seizures (68.1%), 36 atypical absences (76.6%) and 3 tonic seizures (6.4%). EEG backgrounds were slow or parietal θ rhythm, interictal EEG showed 1-4 Hz (predominant 2-3 Hz) generalized spike and wave or poly spike and wave discharges in all cases. Seizures were controlled by antiepileptic drugs (AEDs) in 41 patients (87.2%). Valproate was used in 37. Lamotrigine was used in 26. Mild mental retardation was observed in 10 children after the onset of the illness.

CONCLUSION

The clinical features of MAE included the following: the development was normal before the onset of the illness; the onset of seizure type was often GTCS. All patients had multiple generalized seizure types. Myoclonic atonic seizure was its characteristic seizure type. EEG showed generalized discharges. Early diagnosis and rational choice of AEDs are important for getting a better prognosis.

Ictal video-polygraphic features of perioral myoclonia with absences

There have been few case reports of perioral myoclonia with absences (POMA) because of the lack of video-polygraphic recordings clarifying the electroencephalogram (EEG)-electromyogram (EMG) correlations. We describe one of the first video-polygraphic studies of POMA in a patient who underwent repeated and prolonged split-screen video-polygraphic recordings. The ictal EEG showed generalized and irregular discharges of spikes or multiple spikes and slow waves, while two concomitant EMG patterns appeared: (1) a rhythmic enhancement of the orbicularis oris and masseter muscles on both sides with minimal asymmetry corresponding to perioral movements, and (2) a progressive increment in muscular tone in the mylohyoideus muscle corresponding to oroalimentary automatisms. Myoclonic jerks were inconstantly time-locked to the spike component of the spike-wave complex. The evidence of a complex pattern of activation of the facial muscles suggests that the involvement of subcortical central pattern generators, related to masticatory activity, through the disinhibitory effect of the spike-wave discharge is a possible pathophysiological mechanism underlying POMA.

[Early diagnosis of Dravet's syndrome: contributions from clinical practice and molecular biology]

INTRODUCTION

Alterations in SCN1A gene cause most cases of Dravet syndrome. This finding has increased scientific interest in the syndrome, helping to better define its clinical features and facilitating treatment.

AIMS

To update the knowledge on Dravet syndrome and to discuss the role of the molecular studies in improving early detection and specific management of the syndrome.

DEVELOPMENT

We review the current information on the causes, clinical and electrical characteristics, treatment and complications of Dravet syndrome. Special emphasis is made on early detection.

CONCLUSIONS

The phenotype of Dravet syndrome is now better defined and early detection is already possible. As a consequence, it is now possible to use more specific antiepileptic drugs and to avoid harmful treatments. The benefits of better and prompter control of seizures and earlier cognitive interventions need to be demonstrated in prospective studies of children diagnosed in their first year of life.

[Symptoms and clinical course of epilepsy with myoclonic absences]

There is no comprehensive study so far in Japan on epilepsy with myoclonic absences (EMA), characterized by myoclonic absences (MA) as a specific seizure type. We retrospectively studied 9 patients (4 males and 5 females) with EMA confirmed by ictal video EEG and polygraph (EEG+EMG) recordings. The age at MA onset ranged from 18 to 92 months and the age at the last follow-up ranged from 3 to 39 years. The patients had IQ of 40 to 79. Eight patients had been free from seizures for more than one year at the last follow up. MA was controlled by valproate sodium monotherapy or combination of valproate sodium and ethosuximide with appropriate plasma levels. Generalized tonic clonic seizures and severe mental retardation were not necessarily associated with poor seizure outcome. Patients with long MA duration or MA status epilepticus were prone to be refractory to medication. EMA can be divided into two subgroups based on the seizure outcome, favorable and unfavorable. Further large-scale study is required.

Dravet syndrome: a technologist's perspective

Dravet Syndrome (DS), also known as Severe Myoclonic Epilepsy in Infancy (SMEI) is a rare, primarily genetic disorder which develops in infancy. The characteristics of DS are frequent, prolonged, primarily generalized seizures which occur initially with fever and eventually evolve to multiple afebrile seizure types such as myoclonic, atypical absence, and complex partial seizures. Patients, who are initially developmentally normal, will experience concomitant developmental regression as the syndrome progresses. Because it is a childhood disorder, DS is not well known outside the realm of pediatrics. An astute EEG technologist should be able to recognize key factors both clinically and electrographically which point suspicion to the diagnosis of Dravet Syndrome.

Electroclinical characterization and classification of symptomatic epilepsies with very early onset by multiple correspondence analysis

PURPOSE

To characterize very early onset symptomatic epilepsies electroclinically, to identify meaningful factors to delineate epilepsy syndromes under this category, and to test validity of the current syndromic organization of these epilepsies by the International League Against Epilepsy (ILAE).

METHODS

Subjects were 38 epileptic patients with seizure onset before 3 months of age. We investigated the age of seizure onset, seizure types, myoclonus, EEG features, neuroimaging studies, outcome of seizures and development. We performed multiple correspondence analysis (MCA) to reveal associations among these characteristics and to find important characteristics to divide this epilepsy group into subgroups.

RESULTS

Very early onset epilepsies were characterized by partial seizures and epileptic spasms, especially occurring in combination as a single ictal event (combined seizures), and poor outcome. Suppression-burst (SB), hypsarrhythmia, EEG asymmetry and structural brain abnormalities were common. MCA demonstrated that presence or absence of SB was the most meaningful factor to separate this group into subgroups. MCA on the subgroup with SB revealed a subset with early-onset spasms, partial seizures with single focus, no myoclonus, SB during wakefulness and sleep, no EEG asynchrony, hypsarrhythmia and combined seizures, and another subset with late-onset spasms, partial seizures with multiple foci, myoclonus, EEG asynchrony, no combined seizures, SB during sleep only, no EEG asymmetry, no structural abnormality and no hypsarrhythmia. These corresponded to Ohtahara syndrome and early myoclonic encephalopathy, respectively.

CONCLUSIONS

Very early onset symptomatic epilepsies have the electroclinical characteristics distinct from those with later onset. This study supported the current ILAE organization on this epilepsy group from statistic approach.