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The phenotypic spectrum of SCN8A encephalopathy

2015; Lippincott Williams & Wilkins; Volume: 84; Issue: 5 Linguagem: Inglês

10.1212/wnl.0000000000001211

1526-632X

Jan Larsen, Gemma L. Carvill, Elena Gardella, Gerhard Kluger, G. Schmiedel, Nina Barišić, Christel Depienne, Eva H. Brilstra, Yuan Mang, Jens Erik Nielsen, Martin Kirkpatrick, David Goudie, Rebecca Goldman, Johanna Jähn, Birgit Jepsen, Deepak Gill, Miriam Döcker, Saskia Biskup, Jacinta M. McMahon, Bobby P.C. Koeleman, M. L. Harris, Kees P. J. Braun, Carolien G. F. de Kovel, Carla Marini, Nicola Specchio, Tania Djémié, Sarah Weckhuysen, Niels Tommerup, Mónica Troncoso, L. Troncoso, Andrea Bevot, Markus Wolff, Helle Hjalgrim, Renzo Guerrini, Ingrid E. Scheffer, Heather C. Mefford, Rikke S. Møller, Aarno Palotie, Anna-Elina Lehesjoki, Arvid Suls, Bobby P.C. Koeleman, Carla Marini, Christel Depienne, Dana Craiu, Deb K. Pal, Dorota Hoffman‐Zacharska, Eric Leguern, Federico Zara, Felix Rosenow, Hande Çağlayan, Helle Hjalgrim, Hiltrud Muhle, Holger Lerche, Ingo Helbig, Johanna Jähn, Johannes R. Lemke, José M. Serratosa, Kaja Kristine Selmer, Karl Martin Klein, Katalin Štěrbová, Nina Barišić, Padhraig Gormley, Pasquale Striano, Patrick May, Peter De Jonghe, Renzo Guerrini, Rikke S. Møller, Roland Krause, Rudi Balling, Sanjay M. Sisodiya, Sarah von Spiczak, Sarah Weckhuysen, Stéphanie Baulac, Tiina Talvik, Ulrich Stephani, Vladimı́r Komárek, Yvonne G. Weber,

Neuroscience and Neuropharmacology Research

SCN8A encodes the sodium channel voltage-gated α8-subunit (Nav1.6). SCN8A mutations have recently been associated with epilepsy and neurodevelopmental disorders. We aimed to delineate the phenotype associated with SCN8A mutations.We used high-throughput sequence analysis of the SCN8A gene in 683 patients with a range of epileptic encephalopathies. In addition, we ascertained cases with SCN8A mutations from other centers. A detailed clinical history was obtained together with a review of EEG and imaging data.Seventeen patients with de novo heterozygous mutations of SCN8A were studied. Seizure onset occurred at a mean age of 5 months (range: 1 day to 18 months); in general, seizures were not triggered by fever. Fifteen of 17 patients had multiple seizure types including focal, tonic, clonic, myoclonic and absence seizures, and epileptic spasms; seizures were refractory to antiepileptic therapy. Development was normal in 12 patients and slowed after seizure onset, often with regression; 5 patients had delayed development from birth. All patients developed intellectual disability, ranging from mild to severe. Motor manifestations were prominent including hypotonia, dystonia, hyperreflexia, and ataxia. EEG findings comprised moderate to severe background slowing with focal or multifocal epileptiform discharges.SCN8A encephalopathy presents in infancy with multiple seizure types including focal seizures and spasms in some cases. Outcome is often poor and includes hypotonia and movement disorders. The majority of mutations arise de novo, although we observed a single case of somatic mosaicism in an unaffected parent.