Rima Nabbout

Mutations in the neuronal β-tubulin subunit TUBB3 result in malformation of cortical development and neuronal migration defects

Mutations in the TUBB3 gene, encoding β-tubulin isotype III, were recently shown to be associated with various neurological syndromes which all have in common the ocular motility disorder, congenital fibrosis of the extraocular muscle type 3 (CFEOM3). Surprisingly and in contrast to previously described TUBA1A and TUBB2B phenotypes, no evidence of dysfunctional neuronal migration and cortical organization was reported. In our study, we report the discovery of six novel missense mutations in the TUBB3 gene, including one fetal case and one homozygous variation, in nine patients that all share cortical disorganization, axonal abnormalities associated with pontocerebellar hypoplasia, but with no ocular motility defects, CFEOM3. These new findings demonstrate that the spectrum of TUBB3-related phenotype is broader than previously described and includes malformations of cortical development (MCD) associated with neuronal migration and differentiation defects, axonal guidance and tract organization impairment. Complementary functional studies revealed that the mutated βIII-tubulin causing the MCD phenotype results in a reduction of heterodimer formation, yet produce correctly formed microtubules (MTs) in mammalian cells. Further to this, we investigated the properties of the MT network in patients fibroblasts and revealed that MCD mutations can alter the resistance of MTs to depolymerization. Interestingly, this finding contrasts with the increased MT stability observed in the case of CFEOM3-related mutations. These results led us to hypothesize that either MT dynamics or their interactions with various MT-interacting proteins could be differently affected by TUBB3 variations, thus resulting in distinct alteration of downstream processes and therefore explaining the phenotypic diversity of the TUBB3-related spectrum.

Acute encephalopathy with inflammation-mediated status epilepticus

Fever-induced refractory epileptic encephalopathy in school-aged children (FIRES), and idiopathic hemiconvulsion-hemiplegia syndrome (IHHS) are both triggered by fever, although evidence for a causal microorganism or an autoimmune phenomenon is lacking. FIRES begins in school age with status epilepticus lasting several weeks, involves perisylvian areas including mesial temporal structures, and is followed by pharmacoresistant epilepsy with major cognitive deterioration. IHHS begins in infancy with unilateral clonic status epilepticus and is followed by hemiplegia with pharmacoresistant epilepsy. The aetiology of FIRES and IHHS remains unknown, although clinical features and experimental models point to a likely vicious cycle involving inflammation and seizure activity that depends on the stage of brain maturation. We therefore propose to group these conditions under the concept of acute encephalopathy with inflammation-mediated status epilepticus. In addition to preliminary but encouraging clinical observations, there are theoretical reasons to consider the ketogenic diet as an early means to control both seizures and inflammation.

Monogenic idiopathic epilepsies

Major advances have recently been made in our understanding of the genetic bases of monogenic inherited epilepsies. Direct molecular diagnosis is now possible in numerous inherited symptomatic epilepsies. Progress has also been spectacular with respect to several idiopathic epilepsies that are caused by mutations in genes encoding subunits of ion channels or neurotransmitter receptors. Although these findings concern only a few families and sporadic cases, their potential importance is great, because these genes are implicated in a wide range of more common epileptic disorders and seizure types as well as some rare syndromes. Functional studies of these mutations, while leading to further progress in the neurobiology of the epilepsies, will help to refine genotype-phenotype relations and increase our understanding of responses to antiepileptic drugs. In this article, we review the clinical and genetic data on most of the idiopathic human epilepsies and epileptic contexts in which the association of epilepsy and febrile convulsions is genetically determined.

Absence of mutations in major GEFS+ genes in myoclonic astatic epilepsy

Myoclonic astatic epilepsy (MAE) is a genetically determined condition of childhood onset characterized by multiple generalized types of seizures including myoclonic astatic seizures, generalized spike waves and cognitive deterioration. This condition has been reported in a few patients in generalized epilepsy with febrile seizures plus (GEFS+) families and MAE has been considered, like severe myoclonic epilepsy of infancy (SMEI), to be a severe phenotype within the GEFS+ spectrum. Four genes have been identified in GEFS+ families, but only three (SCN1A, SCNlB, GABRG2) were found in MAE patients within GEFS+ families. We analysed these three genes in a series of 22 sporadic patients with MAE and found no causal mutations. These findings suggest that MAE, unlike SMEI, is not genetically related to GEFS+. Although MAE and SMEI share the same types of seizures, only SMEI patients are sensitive to fever. This is probably its main link to GEFS+. A different family of genes is likely to account for MAE.

FIRES and IHHE: Delineation of the syndromes

Idiopathic hemiconvulsion hemiplegia and epilepsy syndrome (IHHE) and febrile infection–related epilepsy syndrome (FIRES) are rare epileptic syndromes characterized by the occurrence of status epilepticus in a previously healthy child during or closely after a febrile episode. In both syndromes, there is no evidence of central nervous system infection (encephalitis) and the etiology remains unclear. Treatment is disappointing, particularly in FIRES, except for a response to ketogenic diet (KD) in half of patients. In IHHS, children develop hemispheric brain atrophy with contralateral hemiplegia, epilepsy, and a variable degree of cognitive deficit. Patients with FIRES develop refractory epilepsy with severe cognitive deficit affecting the temporal and frontal lobe functions. The role of inflammation is hypothesized with a vicious circle involving inflammation and seizure activity facilitated by brain maturation putting them under the concept of “acute encephalopathy with inflammation‐mediated status epilepticus.”

Brain functional imaging SPECT in agyria-pachygyria

Agyria-pachygyria or lissencephaly type I, a diffuse cortical malformation, provides infantile spasms (IS) which are refractory and persisting after the first decade, an age at which IS have disappeared in the other causes. In order to study the functional postnatal development of the lissencephalic cortex, we measured regional cerebral blood flow (rCBF) using SPECT (Single photon emission computed tomography) and 133Xe in 14 children with lissencephaly, aged from 4 months to 12 years (mean = 40 months) compared to normal children of the same age range and to children with cryptogenic IS aged from 3 months to 3 years (mean = 13 months). rCBF was calculated in frontal (FR) and parieto-temporo-occipital (PTO) cortex as well as the ratio FR/PTO. FR/PTO was higher in lissencephalic patients than in controls (P < 0.001) due to higher FR rCBF (P < 0.001), particularly in patients aged less than 3 years. FR/PTO was also higher in lissencephalic patients than in patients with cryptogenic IS (P < 0.001) also due to higher FR rCBF (P < 0.001). The values of FR/PTO and FR rCBF remained stable during the first years of life and did not exhibit any age- or topography-related changes as they do in controls or in patients with cryptogenic IS. There results suggest that the normal process of postnatal development in the brain is lacking in agyria-pachygyria. That could play a role in determining the persistence of epileptic spasms, the specific seizure type of this malformation.

Arterial Spin Labeling MRI: A step forward in non-invasive delineation of focal cortical dysplasia in children

The aim was to localize the interictal cerebral perfusion abnormalities of focal cortical dysplasia (FCD) in children with Arterial Spin Labeling MRI (ASL) in a retrospective study of nine consecutive children explored with multimodal investigation during interictal periods. We analyzed brain morphology with a 1.5T MRI and a dedicated protocol for epilepsy. Brain perfusion was quantified with pseudo continuous ASL. Brain metabolism was imaged with (18)FDG-PET in six patients. Microvessel histology was studied in five children who underwent epilepsy surgery with CD34 immunostaining on FCD and control samples. Localized decrease of cerebral blood flow (CBF) was found on visual analysis in all patients with ASL. It was co-localized with the structural MRI abnormalities in every case, with PET hypo-metabolism in 5/6 cases, and with histologically proven FCD type IIb in 5/5 cases (all seizure free after surgery). CBF was lower (Kruskal-Wallis test, p=0.001) in FCD than in normal cortex. The total count of CD34+ microvessels was similar in FCD and control cases, but microvasculature showed disorganized architecture. Interictal ASL is a non-invasive method that may help to localize the epileptogenic zone showing hypo-perfusion in FCD. Whether this finding could be generalized to MRI-negative FCD needs to be further studied.

Données récentes sur l'implications des canaux ioniques dans les formes familiales d'épilepsies généralisées idiopathiques associées ou non à des convulsions fébriles

Resume Des avancees majeures ont recemment ete obtenues dans la comprehension des bases genetiques qui sous-tendent les epilepsies a heredite monogenique. Pour plusieurs formes d’epilepsies idiopathiques, l’implication de mutations de genes codant pour des canaux ioniques et des recepteurs-canaux a ete demontree. C’est en particulier le cas pour des epilepsies generalisees idiopathiques dont certaines sont associees a des convulsions febriles. Dans cet article nous passons en revue les donnees cliniques et genetiques recentes concernant ces formes d’epilepsies.

Development and content validation of a preliminary core set of patient- and caregiver-relevant outcomes for inclusion in a potential composite endpoint for Dravet Syndrome

BACKGROUNDnDravet Syndrome (DS) is a rare developmental and epileptic encephalopathy characterized by multiple seizures, frequently prolonged and treatment refractory, with significant developmental disabilities and behavioral and psychiatric disorders. Patients with DS require intensive support and supervision from a caregiver, impacting significantly on both patients and caregivers lives. This study aimed to identify core concepts to measure the impact on both patients and caregivers in future DS clinical trials.nnnMETHODSnQualitative concept elicitation interviews were conducted with caregivers and healthcare professionals involved in caring for children with DS (aged 2-18years) in France to identify important concepts related to the global impact of DS. Interviews explored a range of concepts, including triggers, symptoms, impacts, and coping strategies, from which a conceptual model was developed. A Delphi consensus panel with eight international clinical experts aimed to identify important and relevant endpoints.nnnRESULTSnSeizure was the most commonly reported symptom with DS further impacting childrens cognitive and behavioral functioning. Caregivers identified impact concepts not reported by healthcare professionals. Both groups described additional impacts on wider family members and home modifications. Clinical experts agreed on the inclusion of five patient- and caregiver-relevant concepts for measurement in future DS clinical trials in a composite endpoint. The five concepts for inclusion were; seizures, expressive communication of the child, receptive communication of the child, impact on daily activities, and social functioning of the caregiver.nnnCONCLUSIONSnThis study showed the wider potential impact of DS to extend beyond that of seizures, demonstrating that there is a need for additional patient- and caregiver-relevant concepts to be measured in clinical trials to fully identify the value of therapeutic interventions.

PP01.9 – 2684: Late cognitive delay in Dravet syndrome, after the age of 6 years: Report of four cases

Objective Patients with Dravet syndrome develop a progressive slowing of acquisition from the age of 2 years. Cognitive delay is generally reported after four years of age, without progressive regression. Some variability has been reported and the slowing of acquisitions with development of intellectual disability may occur later up to the fourth year (Buoni et al. 2006; Nabbout et al. 2013; Guzzetta 2011). Methods We report four patients (2 males and 2 females) who preserved a normal or subnormal cognitive level at six years. They were all positive for SCN1A mutation, with mutation de novo in 3/4. Subtypes: one missense, one splicing, one frameshift and one nonsense. They were followed up until a median age of 11 years and 9 months (8 yars 11 months to 13 years 5 months). Only one patient was seizure free from more than one year at the last follow-up. In the others, the frequency of seizures was variable, from yearly to monthly seizures. All received the tritherapy (VPA+STP+CLB) except one. They had longitudinal neuropsychological testing through standardised psychometric tools. The minimum age at last evaluation was 8 years and 11 months. Results At 6 years they all presented an IQ >70 (respectively 95, 82, 78, 96). Two of them have presented a clear decrease in their neuropsychological scores ( Conclusion The stagnation of acquisitions and the cognitive delay in Dravet Syndrome can occur later than what is classically reported in literature, thus implying a different approach in the communication of the prognostic of the cognitive evolution.