O-17 Electroencephalographic characteristics of SYNGAP1 developmental and epileptic encephalopathy, a review of literature and case report

Abstract

Background Mutations on SYNGAP1, which encodes a main protein in the postsynaptic regulating NMDA cascade responsible of the formation and maturation of dendritic spines, were described in patients with intellectual disability, autism spectrum disorder and epilepsy. Since this entity has its own characteristic features, it could be considered as a syndromic type of developmental and epileptic encephalopathy (DEE). Our aim is to review the electroencephalographic features and compare them with the evolution of a 6-year-old girl with a confirmed frameshift mutation. Material and methods A PubMED research was done with the keywords “SYNGAP1”, ”encephalopathy”, “epilepsy” and “EEG or electroencephalography”, of recent case or case series reports that include well described EEG characteristics and compare them with the video-EEG tests performed in our patient. Results The first video-EEG at 5 years old, showed a diffuse slowing background with frontal delta waves and generalized polyspike-wave discharges, that correlated with eyelid myoclonia, neck retropulsion with or without limb myoclonus or fall. Follow-up EEGs also showed multifocal discharges and bioccipital photoparoxysmal response. Conclusion This case provides a complete clinical and video-EEG evidence of a new type of seizures that are particularly characteristic of SYNGAP1 DEE, as well as the dynamical evolution within the years of the patient’s own background, ictal and interictal patterns.