Atypical multifocal Dravet syndrome lacks generalized seizures and may show later cognitive decline

Authors

  • Young Ok Kim,

    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
    2. Department of Paediatrics, School of Medicine, Chonnam National University, Gwangju, Korea
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  • Susannah Bellows,

    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
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  • Jacinta M McMahon,

    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
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  • Xenia Iona,

    1. Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
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  • John Damiano,

    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
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  • Leanne Dibbens,

    1. Epilepsy Research Program, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia
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  • Kent Kelley,

    1. NorthShore University HealthSystem, Evanston, IL, USA
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  • Deepak Gill,

    1. TY Nelson Department of Neurology, The Children's Hospital at Westmead, Sydney, Australia
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  • J Helen Cross,

    1. UCL-Institute of Child Health and Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
    2. Young Epilepsy, Lingfield, UK
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  • Samuel F Berkovic,

    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
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  • Ingrid E Scheffer

    Corresponding author
    1. Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Melbourne, Australia
    2. Florey Institute, Melbourne, Australia
    3. Department of Paediatrics, The University of Melbourne, Royal Children's Hospital, Melbourne, Australia
    • Correspondence to Professor Ingrid E Scheffer, Epilepsy Research Centre, 245 Burgundy Street, Heidelberg, Victoria 3084, Australia. E-mail: scheffer@unimelb.edu.au

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Abstract

Aim

To show that atypical multifocal Dravet syndrome is a recognizable, electroclinical syndrome associated with sodium channel gene (SCN1A) mutations that readily escapes diagnosis owing to later cognitive decline and tonic seizures.

Method

Eight patients underwent electroclinical characterization. SCN1A was sequenced and copy number variations sought by multiplex ligation-dependent probe amplification.

Results

All patients were female (age range at assessment 5–26y) with median seizure onset at 6.5 months (range 4–19mo). The initial seizure was brief in seven and status epilepticus only occurred in one; three were febrile. Focal seizures occurred in four patients and bilateral convulsion in the other four. All patients developed multiple focal seizure types and bilateral convulsions, with seizure clusters in six. The most common focal seizure semiology (six out of eight) comprised unilateral clonic activity. Five also had focal or asymmetric tonic seizures. Rare or transient myoclonic seizures occurred in six individuals, often triggered by specific antiepileptic drugs. Developmental slowing occurred in all: six between 3 years and 8 years, and two around 1 year 6 months. Cognitive outcome varied from severe to mild intellectual disability. Multifocal epileptiform discharges were seen on electroencephalography. Seven out of eight patients had SCN1A mutations.

Interpretation

Atypical, multifocal Dravet syndrome with SCN1A mutations may not be recognized because of later cognitive decline and frequent tonic seizures.

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