Neuropsychological Aspects of Severe Myoclonic Epilepsy in Infancy

Central neurogenetic signatures of the visuomotor integration system

Visuomotor impairments characterize numerous neurological disorders and neurogenetic syndromes, such as autism spectrum disorder (ASD) and Dravet, Fragile X, Prader-Willi, Turner, and Williams syndromes. Despite recent advances in systems neuroscience, the biological basis underlying visuomotor functional impairments associated with these clinical conditions is poorly understood. In this study, we used neuroimaging connectomic approaches to map the visuomotor integration (VMI) system in the human brain and investigated the topology approximation of the VMI network to the Allen Human Brain Atlas, a whole-brain transcriptome-wide atlas of cortical genetic expression. We found the genetic expression of four genes-TBR1, SCN1A, MAGEL2, and CACNB4-to be prominently associated with visuomotor integrators in the human cortex. TBR1 gene transcripts, an ASD gene whose expression is related to neural development of the cortex and the hippocampus, showed a central spatial allocation within the VMI system. Our findings delineate gene expression traits underlying the VMI system in the human cortex, where specific genes, such as TBR1, are likely to play a central role in its neuronal organization, as well as on specific phenotypes of neurogenetic syndromes.

Autism spectrum disorder and cognitive profile in children with Dravet syndrome: Delineation of a specific phenotype

OBJECTIVE

We aimed to assess a cohort of young patients with Dravet syndrome (DS) for intellectual disability (ID) and autism spectrum disorder (ASD) using standardized tools and parental questionnaires to delineate their specific profiles.

METHODS

We included 35 patients with DS aged 24 months to 7 years, excluding patients with a developmental age (DA) <18 months (n = 5). We performed specific tests adapted for ID (Psychoeducational Profile, Third Edition [PEP-3]), in addition to the Child Development Inventory (CDI) and Vineland Adaptive Behavior Scales, Second Edition (VABS-II) questionnaires. We used 2 standardized tools for ASD: the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) and the Autism Diagnostic Interview-Revised (ADI-R). We compared the with parental questionnaires and the VABS-II, and with ASD characteristics.

RESULTS

PEP-3 subscales showed pathologic development in all but one patient (97%): ID in 23 of 30 (77%), and borderline cognitive functioning in 6 of 30 (22%). Eleven patients (39%) had ASD and 2 (7%) had a Social Communication Disorder (SCD) diagnosis. We found no difference between PEP-3 and CDI categorization except for fine motor skills. We found significant negative correlations between ADOS-2 and PEP-3 for the majority of scores. For patients aged older than 50 months, 2 groups emerged (ASD/no ASD) with significant difference in DA. The logistic regression for ASD diagnosis explained by VABS-II showed a significant effect for Socialization, Motor Skills, and Adaptive Behavior.

SIGNIFICANCE

We found a high prevalence of ID in patients with DS. ID is characterized by expressive and comprehensive communication deficits in addition to visuospatial difficulties. ASD showed a specific profile with a relative preservation of social skills, emphasizing a possible underdiagnosis. Parental questionnaires can provide a good assessment of cognitive profile and might allow the difficulty of addressing cognitive scales in DS to be overcome. The profile of ID and ASD should help to establish early adapted rehabilitation programs and emphasizes the global need for care beyond seizures in DS and other developmental epileptic encephalopathies.

Dysarthria and broader motor speech deficits in Dravet syndrome

OBJECTIVE

To analyze the oral motor, speech, and language phenotype in 20 children and adults with Dravet syndrome (DS) associated with mutations in SCN1A.

METHODS

Fifteen verbal and 5 minimally verbal DS patients with SCN1A mutations (aged 15 months-28 years) underwent a tailored assessment battery.

RESULTS

Speech was characterized by imprecise articulation, abnormal nasal resonance, voice, and pitch, and prosody errors. Half of verbal patients had moderate to severely impaired conversational speech intelligibility. Oral motor impairment, motor planning/programming difficulties, and poor postural control were typical. Nonverbal individuals had intentional communication. Cognitive skills varied markedly, with intellectual functioning ranging from the low average range to severe intellectual disability. Language impairment was congruent with cognition.

CONCLUSIONS

We describe a distinctive speech, language, and oral motor phenotype in children and adults with DS associated with mutations in SCN1A. Recognizing this phenotype will guide therapeutic intervention in patients with DS.

Overall management of patients with Dravet syndrome

Dravet syndrome, or as it was called in the past 'severe myoclonic epilepsy in infancy', is a drug-resistant epilepsy first described by Charlotte Dravet in 1978. Besides the well-known and well-described therapy resistance, Dravet syndrome dramatically impacts the development and behaviour of the affected children. As it is still not a curable disease, families need to be taught how to cope with the disorder and will require assistance from both clinical and non-clinical structures. At the onset of the disease, many questions arise regarding the diagnosis of Dravet syndrome, the severity of the illness and its deleterious effects, and the management of seizures, especially the long-lasting status epilepticus. Once the diagnosis has been established, severe convulsions, often unpredictable and long-lasting, are still a major worry, but developmental and behavioural problems also rapidly become a serious concern. Later on, nearly all parents will have a child who becomes an adult with special needs, requiring specialised attention from professionals.

Dravet syndrome history

Severe myoclonic epilepsy of infancy (SMEI) is a complex form of epilepsy that was first described in France in 1978. Because the myoclonic component of this epilepsy is not always present and because some variability has been observed in the symptomatology, the name was changed to Dravet syndrome in 1989. The genetic aetiology of this epilepsy was discovered in 2001, and since then numerous studies have contributed to a better knowledge of the disease. Around 70% of affected patients are carriers of a mutation on the alpha subunit of the SCN1A gene. An accurate analysis of the clinical features leads to the distinction between typical and atypical forms, both with the same unfavourable prognosis and the same genetic background. However, many studies are being conducted in order to establish correlations between phenotypes and genotypes, and to understand the factors underlying the cognitive impairment of the affected patients.

Cognitive development in Dravet syndrome: a retrospective, multicenter study of 26 patients

PURPOSE

To clarify the role of epilepsy and genetic background in determining the cognitive outcome of patients with Dravet syndrome.

METHODS

In this retrospective study, we reviewed the clinical history and cognitive development of 26 patients who had been followed with standardized evaluations since seizure onset. The cognitive outcome was quantified as differential general quotient (dGQ) between ages 12 and 60 months. Statistical analysis correlated the dGQ with genotype and epilepsy course.

KEY FINDINGS

Epilepsy started at the mean age of 5.6 months. All patients experienced prolonged convulsive seizures, whereas absences and myoclonus were reported in 17. Cognitive outcome was poor in almost all patients; the mean dGQ was 33 points, varying from 6-77 points. The analysis of individual cognitive profiles identified seven patients in whom the dGQ was <20 points; the main clinical characteristic in this subset of patients was lack of early absences and myoclonus. The statistical analysis of the whole series failed to reveal significant differences in cognitive outcome with regard to the presence of SCN1A mutations and their type. In particular, mutation-carrier patients with the best cognitive outcome harbored either missense or truncating mutations.

SIGNIFICANCE

Dravet syndrome encompasses different epileptic and cognitive phenotypes that probably result from both genetic and epigenetic factors. In this series, early appearance of myoclonus and absences was associated with the worst cognitive outcome.

Coping with a child with Dravet syndrome: insights from families

Dravet syndrome is a truly catastrophic childhood-onset epilepsy. Families are faced with repeated episodes of status epilepticus, intractable seizures, mental handicap, behavior disorders, and a life of dependency; understandably, coping with Dravet syndrome is very difficult. Twenty-four families with a child with Dravet syndrome were interviewed and identified some practical suggestions to improve their daily life. These included inserting an indwelling venous access device, creating a portable microenvironment, writing an emergency department protocol, establishing emergency routines for the family, assigning a parent on call to lessen the effect on siblings, creating personal time to decrease parental stress, finding respite care, and contacting an Internet support group. Unresolved and common issues included transition to adult care, the utility of early diagnosis, and social isolation. These solutions and issues may be helpful to many families with a child with Dravet syndrome and possibly other severe childhood-onset epilepsies.

Neuropsychological deficits in childhood epilepsy syndromes

Seizure disorders are relatively common in childhood, and the International League Against Epilepsy (ILAE) provides a hierarchical classification system to define seizure types. At the final level of classification, specific epilepsy syndromes are defined that represent a complex of signs and symptoms unique to an epilepsy condition. The present review discusses the issues related to several of these epilepsy syndromes in childhood, including those classified as generalized idiopathic epilepsies (e.g., childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy), focal epilepsies (benign rolandic epilepsy, occipital epilepsy, temporal lobe epilepsy, frontal lobe epilepsy) and the "epileptic encephalopathies," including Dravet's Syndrome, West Syndrome, Lennox-Gastaut Syndrome, Myoclonic Astatic Epilepsy, and Landau-Kleffner Syndrome. For each syndrome, the epidemiology, clinical manifestations, treatments, and neuropsychological findings are discussed.

Dravet syndrome (severe myoclonic epilepsy in infancy): a retrospective study of 16 patients

To report the authors' experience with diagnosis and management of Dravet syndrome, or severe myoclonic epilepsy in infancy, in the era of commercially available genetic testing, the authors performed a retrospective study of 16 patients diagnosed with Dravet syndrome at a tertiary care pediatric epilepsy center. They analyzed their clinical presentation, electroencephalographic findings, genetic (SCN1A gene) results, and treatment responses and compared the findings to previous reports. The patients presented with all the previously described characteristics of Dravet syndrome. Six of the 7 patients (86%) who were tested for SCN1A mutations had positive results. The best treatment combinations included topiramate, valproate, or the ketogenic diet. Dravet syndrome is a well-defined epileptic syndrome that needs larger recognition, particularly because commercial testing for SCN1A gene mutations is now available in the United States. Despite its reputation for seizure intractability, several treatment options may be particularly helpful, whereas others need to be avoided.

Cognitive and Behavioral Outcomes of Epileptic Syndromes: Implications for Education and Clinical Practice

The educational and social progress of a child with epilepsy depends not only on seizure control but also on cognitive and behavioral factors. The various epilepsy syndromes of childhood and adolescence differ greatly in terms of cognitive and behavioral outcome. A high proportion of babies who have West syndrome and children who have Dravet syndrome (severe myoclonic epilepsy in infancy) will have long-term cognitive and behavioral problems. The Lennox-Gastaut syndrome also often has a poor prognosis in this regard. Children with the Landau-Kleffner syndrome have a variable prognosis, some regain speech and others have permanent speech impairment. Benign childhood epilepsy with centrotemporal spikes is now recognised as lying on a spectrum with the Landau-Kleffner syndrome: mild cases have few if any cognitive or behavioral problems but others may have quite severe difficulties. People with juvenile myoclonic epilepsy may have characteristics suggesting frontal lobe impairment. The educational and social impairments associated with the epilepsy syndromes of childhood and adolescence are of major importance but they have been the subject of remarkably few well-performed studies. The impairments are not always necessarily permanent and it seems highly likely that the cognitive and behavioural outcome of at least some of these syndromes can be influenced greatly by early effective treatment with either antiepileptic medication or surgery.