Publications by authors named "Claire Bar"

10 Publications

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Developmental and epilepsy spectrum of KCNB1 encephalopathy with long-term outcome.

Epilepsia 2020 11 21;61(11):2461-2473. Epub 2020 Sep 21.

Reference Center for Rare Developmental Abnormalities CLAD-Ouest, Rennes University Hospital Center, Rennes, France.

Objective: We aimed to delineate the phenotypic spectrum and long-term outcome of individuals with KCNB1 encephalopathy.

Methods: We collected genetic, clinical, electroencephalographic, and imaging data of individuals with KCNB1 pathogenic variants recruited through an international collaboration, with the support of the family association "KCNB1 France." Patients were classified as having developmental and epileptic encephalopathy (DEE) or developmental encephalopathy (DE). In addition, we reviewed published cases and provided the long-term outcome in patients older than 12 years from our series and from literature.

Results: Our series included 36 patients (21 males, median age = 10 years, range = 1.6 months-34 years). Twenty patients (56%) had DEE with infantile onset seizures (seizure onset = 10 months, range = 10 days-3.5 years), whereas 16 (33%) had DE with late onset epilepsy in 10 (seizure onset = 5 years, range = 18 months-25 years) and without epilepsy in six. Cognitive impairment was more severe in individuals with DEE compared to those with DE. Analysis of 73 individuals with KCNB1 pathogenic variants (36 from our series and 37 published individuals in nine reports) showed developmental delay in all with severe to profound intellectual disability in 67% (n = 41/61) and autistic features in 56% (n = 32/57). Long-term outcome in 22 individuals older than 12 years (14 in our series and eight published individuals) showed poor cognitive, psychiatric, and behavioral outcome. Epilepsy course was variable. Missense variants were associated with more frequent and more severe epilepsy compared to truncating variants.

Significance: Our study describes the phenotypic spectrum of KCNB1 encephalopathy, which varies from severe DEE to DE with or without epilepsy. Although cognitive impairment is worse in patients with DEE, long-term outcome is poor for most and missense variants are associated with more severe epilepsy outcome. Further understanding of disease mechanisms should facilitate the development of targeted therapies, much needed to improve the neurodevelopmental prognosis.
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November 2020

Expanding the genetic and phenotypic relevance of KCNB1 variants in developmental and epileptic encephalopathies: 27 new patients and overview of the literature.

Hum Mutat 2020 01 4;41(1):69-80. Epub 2019 Oct 4.

Departments of Neurology and Paediatrics, Royal Children's Hospital, University of Melbourne, Melbourne, Victoria, Australia.

Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with early-onset DEE. KCNB1 encodes the α subunit of the delayed rectifier voltage-dependent potassium channel K 2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of K 2.1. We also report the first inherited variant (p.Arg583*). KCNB1-related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty-five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C-terminal domain are associated with a less-severe epileptic phenotype. Overall, this report provides an up-to-date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms.
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January 2020

Experience of follow-up, quality of life, and transition from pediatric to adult healthcare of patients with tuberous sclerosis complex.

Epilepsy Behav 2019 07 9;96:23-27. Epub 2019 May 9.

Department of Pediatric Neurology, Reference Centre for Rare Epilepsies, Necker-Enfants Malades, AP-HP, Paris, France; Laboratory of Translational Research for Neurological Disorders, INSERM UMR 1163, Imagine Institute, Paris, France; Université Paris Descartes -Sorbonne Paris Cité, Imagine Institute, Paris, France. Electronic address:

Introduction: Tuberous sclerosis complex (TSC) is a multisystemic genetic disease with high clinical variability and age-related manifestations. These characteristics add to the complexity of transition to adulthood. This study aimed to explore the perception of medical follow-up and transition experience in a large group of patients with TSC who presented epilepsy in childhood.

Method: This multicenter French study included patients with TSC aged 18 years or older who developed epilepsy before the age of 16 years. A questionnaire specifically designed for the study explored patients' opinion through 270 questions covering different aspects of their social, familial, professional, and medical courses.

Results: The questionnaire was sent to 72 patients, and 60 patients were included in the study (83% response rate) with a mean age of 32 years (18-55 years). Cognitive impairment was present in 80% of patients, and half of questionnaires were completed by the family. Pediatric care was coordinated by the child neurologist and was more regular and multidisciplinary than adult care. Epilepsy had the best follow-up followed by renal issues. Unmet needs were identified for psychiatric and behavioral disorders, both in children and adults. Respondents considered the help in achieving autonomy better in adult care. Only 50% of patients with a normal intellectual development had clear knowledge about their disease and the need for a regular monitoring. Two-thirds of respondents estimated that they had a transition experience between 16.5 and 21-year-old, considered as good in 60% of them. Seventy percent felt continuity between pediatric and adult care, and only 3% of respondents felt that their care would have been better if they were still followed in pediatric healthcare system. The change of care structure and/or caregivers was the most stressful factor during transition and transfer.

Conclusion: This study highlights persistent issues in the regularity and coordination of the follow-up of patients with TSC despite established international guidelines. Although most patients had a positive transition experience, there is still an urgent need to optimize transition programs. This would be essential to maintain care continuity between pediatric and adult health systems, especially for patients with TSC with epilepsy and high rate of cognitive and psychiatric impairments.
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July 2019

Early magnetic resonance imaging to detect presymptomatic leptomeningeal angioma in children with suspected Sturge-Weber syndrome.

Dev Med Child Neurol 2020 02 3;62(2):227-233. Epub 2019 May 3.

Department of Paediatric Neurology, Hôpital Necker-Enfants Malades, Reference Centre for Rare Epilepsies, APHP, Bordeaux, France.

Aim: We aimed to evaluate the contribution of early magnetic resonance imaging (MRI) for the presymptomatic diagnosis of Sturge-Weber syndrome (SWS) in infants with a facial port-wine birthmark (PWB).

Method: Asymptomatic infants with a facial PWB who performed a first MRI scan before 3 months and a second MRI scan after 9 months were included in this study. Leptomeningeal enhancement on T1-weighted imaging and four indirect signs of leptomeningeal angioma (choroid plexus enlargement, cerebral atrophy, signal inversion of the white matter with T2 hyposignal, and T1 hypersignal) were screened on the first MRI scan and correlated with clinical and/or radiological diagnosis of SWS.

Results: Thirteen of 30 included patients had SWS with leptomeningeal angioma. Eleven had a leptomeningeal enhancement on the first MRI scan and 10 had associated indirect signs. The presence of a direct or at least one indirect sign of leptomeningeal angioma on the first MRI scan confirmed the diagnosis of SWS with a sensitivity of 100 per cent (95% confidence interval 75-100%) and a specificity of 94 per cent (71-100%).

Interpretation: Early diagnosis of SWS is possible on contrast-enhanced MRI performed in asymptomatic infants with a facial PWB before the age of 3 months. This early detection would help to select patients who may benefit from early neuroprotective intervention.

What This Paper Adds: Specific magnetic resonance imaging markers provide early diagnosis of leptomeningeal angioma in Sturge-Weber syndrome (SWS). Presymptomatic diagnosis of SWS should help to select patients for early therapy intervention.
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February 2020

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 Aug;21(8):1897-1898

APHP, Service de genetique medicale, Necker- Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.
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August 2019

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 04 12;21(4):837-849. Epub 2018 Sep 12.

APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

Purpose: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
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April 2019

Spikes might precede seizures and predict epilepsy in children with Sturge-Weber syndrome: A pilot study.

Epilepsy Res 2018 07 28;143:75-78. Epub 2018 Mar 28.

Reference Centre for Rare Epilepsies, Department of Pediatric Neurology, Hôpital Necker-Enfants Malades, APHP, Paris, France; INSERM U1129, Paris, France; Paris Descartes University, Sorbonne Paris Cité, CEA, Gif sur Yvette, France. Electronic address:

Purpose: Sturge-Weber syndrome (SWS) is a neurocutaneous disorder characterized by a facial port-wine stain, a glaucoma, and a leptomeningeal angioma. Epilepsy occurs in more than 75% of affected children, and seizures occurring in the first year of life are associated with a poor neurological prognosis. The aim of this study was to identify possible predictive markers of epilepsy on electroencephalogram (EEG) performed prior to seizure onset in children with SWS.

Methods: This study included children with a diagnosis of SWS who had an EEG performed prior to seizure onset. Patients who did not develop epilepsy had a minimum follow-up of 3-years. We compared EEG characteristics of patients who developed epilepsy with patients who did not develop epilepsy by the time of their follow-up.

Results: Eleven children were included in this study. EEG was performed at the median age of 2.1 months (range 1.0-22.1). Six children developed seizures with a time interval between EEG and seizure onset ranging from 2 days to 21 months. EEG background activity was asymmetric in 8 patients, 5 of whom later developed epilepsy. Focal interictal spikes or sharp waves were exclusively recorded in patients who developed later epilepsy (4 out of 6). One of these patients had a supposed false positive EEG as he did not developed epilepsy until 21 months later and one patient had a false negative EEG with seizures occurring 2 days after a normal EEG.

Conclusion: Spikes on EEG might be a useful marker to identify patients with SWS at risk of developing epilepsy. Their predictive value should be assessed in larger prospective studies.
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July 2018

Childhood idiopathic spinal cord infarction: Description of 7 cases and review of the literature.

Brain Dev 2017 Nov 31;39(10):818-827. Epub 2017 May 31.

Service de Neurologie Pédiatrique, Hôpital Pellegrin-Enfants, CHU de Bordeaux, France.

Objectives: To describe the clinical course, neuroimaging findings and functional outcome of idiopathic spinal cord infarction (SCI) in adolescents.

Methods: Retrospective and descriptive analyses of seven patients with idiopathic SCI and 50 additional cases from the literature were included. Data collected concerned clinical presentation, MRI findings, initial diagnosis, treatments and functional outcome at the last medical visit.

Results: Mean age at presentation was 13.2years (range 13-15). All patients presented a sudden and painful acute myelopathy with <24h time to maximal symptoms manifestation. A suspected trigger related to a minor effort was reported in 3/7 cases. Six patients presented with paraplegia, one with paraparesis. All had bladder dysfunction needing catheterization. Three patients had an initial misdiagnosis. Initial MRI was considered as normal in 2 cases. In the 5 other cases, T2-weighted-MR images showed hyperintensity within the thoracolumbar spinal cord, affecting mostly the anterior spinal artery territory. Evidence for associated spinal growth dystrophy were present in 6/7 cases. Mean follow-up time was 27.4months (range 3-46): 2 patients recovered autonomous ambulation, 4 patients regained walking ability with aids and one child (the shortest follow-up) remained wheelchair-dependent. A neurogenic bladder was still reported in 6/7 children at the last visit. Complementary analyses with literature cases were consistent with the findings obtained in our cohort.

Conclusion: Idiopathic SCI typically occurs in adolescence with a rapid onset and painful acute myelopathy. The MRI shows a T2-hyperintense signal within the spinal cord and provides evidence for an ischemic mechanism. Etiology remains unclear in most cases even though some specific risk factors for this age must play an important role in the pathogenesis, such as mechanical constraints on the immature spine.
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November 2017

Vascular impairment as a pathological mechanism underlying long-lasting cognitive dysfunction after pediatric traumatic brain injury.

Neurochem Int 2017 Dec 1;111:93-102. Epub 2017 Apr 1.

CNRS UMR 5287, INCIA, University of Bordeaux, France; Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, USA. Electronic address:

Traumatic brain injury (TBI) is the leading cause of death and disability in children. Indeed, the acute mechanical injury often evolves to a chronic brain disorder with long-term cognitive, emotional and social dysfunction even in the case of mild TBI. Contrary to the commonly held idea that children show better recovery from injuries than adults, pediatric TBI patients actually have worse outcome than adults for the same injury severity. Acute trauma to the young brain likely interferes with the fine-tuned developmental processes and may give rise to long-lasting consequences on brain's function. This review will focus on cerebrovascular dysfunction as an important early event that may lead to long-term phenotypic changes in the brain after pediatric TBI. These, in turn may be associated with accelerated brain aging and cognitive dysfunction. Finally, since no effective treatments are currently available, understanding the unique pathophysiological mechanisms of pediatric TBI is crucial for the development of new therapeutic options.
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December 2017

Catathrenia in a four-year-old boy: a first case report.

Sleep Med 2016 04 13;20:131-3. Epub 2016 Jan 13.

Department of Clinical Neurophysiology, Hôpital Pellegrin, Bordeaux, France. Electronic address:

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April 2016