Electroclinical Spectrum of SCN1A Mutation Positive Dravet syndrome Patients

Abstract

Purpose: With the widespread use of SCN1A genetic tests, electroclinical spectrum observed in patients with SCN1A mutation is expanding beyond classic Dravet syndrome. This study reviews the electroclinical features of SCN1A mutation positive patients to discuss the point of consideration for diagnosing Dravet syndrome. Methods: We reviewed the electroclinical features of 55 patients with confirmed SCN1A mutations focusing on core features of Dravet syndrome. SCN1A mutational analysis was performed with direct Sanger sequencing and multiple ligation dependent probe amplification. Results: Twenty-nine of 55 patients were male. The mean age of seizure onset was 5.8 months (range 1 day – 12.0 months). Fifty-three percent patients presented fever or illness and 29% patients had prolonged seizure at seizure onset. Eight-five percent patient showed generalized tonic-clonic seizure or hemi-clonic seizure as first seizure. All patients showed normal development before seizure onset. Twenty-five (83%) patients showed normal findings in initial interictal electroencephalography (EEG). At steady state, patients show various seizures such as focal seizures (78%), hemi-clonic seizures (59%), myoclonic seizures (40%) and atypical absence seizures (28%). Generalized epileptiform discharges was detected in 39% patients and focal epileptiform discharges were confirmed in 65% patients. All patients had the resistant to antiepileptic drugs and showed developmental delay or regression after 2 years old. Conclusion Dravet syndrome patients with SCN1A mutation have consistent characteristics at seizure onset including age, interictal EEG finding, the type of seizure. However, at steady state, seizure semiology and EEG patterns show significant variations between patients. Careful investigation about the mode of early stage is crucial for diagnosing Dravet syndrome