Abstracts

Rationale: Dravet syndrome is a severe infantile onset epileptic encephalopathy associated with mutations in the SCN1A gene encoding the alpha subunit of the voltage gated sodium channel Nav1.1. There is a well-recognised excess mortality in children with the syndrome. Our aim was to analyse electro-clinical characteristics within a large cohort of SCN1A positive cases to determine whether any disease characteristics are associated with sudden unexpected death in epilepsy (SUDEP) or death following status epilepticus. Methods: We prospectively collected data on 207 SCN1A mutation positive Dravet syndrome cases over a five year period. All genetic diagnostic studies were performed in our centre. From structured referral data we examined a comprehensive range of clinical characteristics including epilepsy phenotype, seizure precipitants, vaccination history, EEG data, imaging studies, mutation type and neuro-cognitive sequelae. Differences between deceased and non-deceased patients were determined using Mann-Whitney U test for continuous variables and chi-square statistics for categorical differences. Where assumptions for a Chi-square test are not fulfilled, Fisher's exact probability is given. Results: In our cohort of 207 patients with classical Dravet syndrome we have had 8 reported epilepsy-related deaths (4%). 5 cases were designated SUDEP and 3 deaths were associated with status epilepticus. Epilepsy related death was significantly more common in infants that had abnormal interictal EEG findings in the first year of life (6/48, 13%) compared to those with a normal interictal EEG in the first year of life (1/58, 2%; Χ² = 4.9, df = 1, p = 0.045). One or more previous episodes of status epilepticus were more common in the deceased patients (7/8, 88%) compared to the non-deceased patients (154/195, 79%), however this difference did not reach statistical significance. None of the remaining factors including mutation type (truncating vs missense), vaccination history, age at onset of seizures, seizure types, imaging studies or neuro-cognitive sequelae could be associated with epilepsy related death. Conclusions: Identifying factors that are associated with SUDEP or death due to status epilepticus are important to inform counselling. Identifying risk factors will encourage early syndrome specific therapy. Prevention of status epilepticus with regular medication and emergency protocols is important.