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(Abst. 1.118), 2014

Authors: Elena Gardella, Jan Larsen, Markus Wolff, Gudrun Schmiedel, Martin Kirkpatrick, Nina Barisic, Christel Depienne, Monica Troncoso, Birgit Jepsen, M. Nikanorova, Ledia Troncoso, Andrea Bevot, Helle Hjalgrim, S. Beniczky and Rikke Møller
Content: Rationale: SCN8A mutations have been recently associated with early infantile epileptic encephalopathy with a broad phenotypic spectrum. We aim to further delineate the interictal and ictal video-EEG features of a peculiar clinical subgroup of patients affected by early onset SCN8A-related encephalopathy and epilepsy with a poor prognosis. Methods: We studied 9 SCN8A positive patients, age range: 8 months-16 years. They underwent clinical and neurophysiologic investigations including prolonged video-polygraphic recordings during wakefulness and sleep. Results: Epilepsy onset occurred at a mean age of 5 months with polymorphic, drug resistant seizures, cognitive deterioration and pyramidal/extra-pyramidal signs ± loss of eye contact (6/9pt). Non-convulsive status epilepticus occurred in 5/9 and SUDEP in 2/9 patients. Interictal EEG at epilepsy onset was normal in 5/9 patients; during the follow up in all cases occurred progressive background deterioration and focal/multifocal spike-and-waves abnormalities, predominant in the temporo-occipital regions and/or generalized spike waves. Nocturnal sleep EEG (3/9 patients) was normally structured. Ictal video-EEG recordings were obtained in 4/9 patients (follow-up 10-25 months); all seizure types have been documented. Patients had both focal and generalized seizures (FS,GS), the latter consisting of GTCS, pseudo-absences, spasms and myoclonus. FS were usually prolonged (3-5 min), with prominent hypomotor and vegetative semiology, evolving to asymmetric tonic/tonic-clonic manifestations ± secondary generalization. Ictal EEG showed diffuse EEG desynchronization (GS) or post-temporal seizure onset (FS), slow spreading and migration of the ictal discharge (2/4 patients) from one hemisphere to the contralateral during the same seizure. Conclusions: Despite the description of a heterogeneous epileptic phenotype associated to SCN8A encephalopathy, our patients exhibit a distinctive ictal and interictal EEG pattern, suggesting an epileptogenic dysfunction in the temporo-occipital regions, also confirmed from the recurrence of cortical visual impairment. We also speculate that the presence of ictal vegetative symptoms and the long seizures duration with frequent secondary generalization could represent risk factors for SUDEP. Awareness of this distinctive phenotype will likely enhance recognition of the disorder.