SCN2A developmental and epileptic encephalopathy in an infant with bilateral polymicrogyria and opercular dysplasia

Introduction

SCN2A mutations have been associated with a wide phenotypic spectrum that includes, among others, developmental and epileptic encephalopathy (DEE), usually not associated with any brain structural counterpart.

Case description

We report the occurrence of a super-refractory status epilepticus (SRSE) in a 2-month-old infant, who presented at birth with refractory neonatal seizures attributed to an extensive bilateral polymicrogyria and cortical dysplasia. Upon his SRSE, he responded radically to the sodium-channel blocker phenytoin with complete seizure resolution and has remained seizure free during the 2-year follow-up period. A SCN2A pathogenic variant was found with predicted gain-of-function effect. Notably, brain MRI findings during the neonatal ictal phase showed signs of hypoxia with cytotoxic and vasogenic oedema, corresponding to the ictal localisation. These changes were not observed upon repetition of the brain MRI during the SRSE at 2 months of age, perhaps suggesting increased neonatal vulnerability to hypoxia in the presence of an SCN2A variant, that modifies over time.

Conclusion

Our case report highlights the importance of challenging our clinical management in the presence of refractory seizures attributed solely to a structural cause, with genetic testing providing a key insight for therapeutic management.