Unusual association of SCN2A epileptic encephalopathy with severe cortical dysplasia detected by prenatal MRI

Abstract

We present an atypical association of SCN2A epileptic encephalopathy with severe cortical dysplasia. SCN2A mutations are associated with epileptic syndromes from benign to extremely severe in absence of such macroscopic brain findings. Prenatal MRI (Magnetic Resonance Imaging) in a 32 weeks fetus, with US (Ultrasonography) diagnosis of isolated ventriculomegaly showed CNS (Central Nervous System) dysplasia characterized by lack of differentiation between cortical and subcortical layers, pachygyria and corpus callosum dysgenesis. Postnatal MRI confirmed the prenatal findings. On day 6 the baby presented a focal status epilepticus, partially controlled by phenobarbital, phenytoin, and levetiracetam. After three weeks a moderate improvement in seizure control has been achieved with carbamazepine. Exome sequencing detected a de novo heterozygous mutation in the SCN2A gene, encoding the α_II-subunit of a sodium channel. The patient findings expand the phenotype spectrum of SCN2A mutations to epileptic encephalopathies with macroscopic brain developmental features.

Keywords: Cortical dysplasia; Epileptic encephalopathy; Fetal MRI; Prenatal diagnosis; SCN2A.