Introduction Dravet syndrome (DS), or severe myoclonic epilepsy of infancy (SMEI), is a drug resistant epileptic encephalopathy with onset in the first year of life. It is characterised by prolonged tonic-clonic seizures typically provoked by fever and infections, and cognitive decline. Diagnosis may be relatively delayed in presence of another pre-existing condition that predisposes to subsequent development of epilepsy.
Case discussion We describe a 2 year old boy, born at term with significant perinatal asphyxia leading to grade 3 hypoxic ischaemic encephalopathy, with seizures terminating by Day 5. Despite a stormy neonatal start, he was developing appropriately until seizures recurred at 5 months of age. Initially, seizures consisted of multiple brief afebrile multi focal seizures during periods of intercurrent illness. This was initially attributed to severe hypoxic ischaemic encephalopathy at birth predisposing to subsequent development of epilepsy. However, over the next few months this evolved into a drug resistant epileptic encephalopathy characterised by frequent episodes of afebrile and febrile status epilepticus, hemi-convulsions and myoclonic jerks. From 13 months, his nueodevelopment and head growth started to falter. Cognitive regression became quite apparent in the second year of life.
MRI brain on Day 6 showed ischaemic injury to white matter in watershed areas with increased signal over lentiform nucleus. MRI at 11 months showed non-specific white matter changes without evidence of any cortical damage or other structural abnormality to account for refractory epilepsy. Repeated early interictal EEGs were normal.
In view of polymorphic multidrug resistant refractory seizures and a relatively normal MRI brain and EEG, an alternative aetiology for his epilepsy was considered. Genetic testing at 15 months showed pathogenic mutation of SCN1A gene. Anti-epileptic drug therapy was optimised for Dravet syndrome. A combination Stiripentol, Valproate and Clobazam has dramatically reduced the seizure burden, although cognitive progress has remained slow. Correct diagnosis has been vital in counselling carers regarding not only prognosis, but also avoidance of triggers.
Conclusion This case report emphasises the need to constantly review the aetiology in refractory epilepsy even with an apparent underlying cause, especially if there are unexplained atypical features.