SCN8A Mutation in Infantile Epileptic Encephalopathy: Report of Two Cases

Mechanisms of infantile epileptic spasms syndrome: What have we learned from animal models?

The devastating developmental and epileptic encephalopathy of infantile epileptic spasms syndrome (IESS) has numerous causes, including, but not limited to, brain injury, metabolic, and genetic conditions. Given the stereotyped electrophysiologic, age-dependent, and clinical findings, there likely exists one or more final common pathways in the development of IESS. The identity of this final common pathway is unknown, but it may represent a novel therapeutic target for infantile spasms. Previous research on IESS has focused largely on identifying the neuroanatomic substrate using specialized neuroimaging techniques and cerebrospinal fluid analysis in human patients. Over the past three decades, several animal models of IESS were created with an aim to interrogate the underlying pathogenesis of IESS, to identify novel therapeutic targets, and to test various treatments. Each of these models have been successful at recapitulating multiple aspects of the human IESS condition. These animal models have implicated several different molecular pathways in the development of infantile spasms. In this review we outline the progress that has been made thus far using these animal models and discuss future directions to help researchers identify novel treatments for drug-resistant IESS.

A Novel SCN8A mutation in a case of early-onset infantile epileptic encephalopathy: A Case Report

SCN8A gene encodes sodium channel alpha subunit Nav1.6, and its mutation is associated with Early Infantile Epileptic Encephalopathy-13 (EIEE-13). The mean age of onset is 4-5 months. The phenotype of SCN8A mutation varies from benign epilepsy syndromes, movement disorder, intellectual disability to severe epileptic syndromes with different types of seizures. We hereby report a case of a one-year old female who had an onset of infantile spasms on the seventeenth day of life, which gradually progressed to focal, multifocal, GTCS, and epileptic encephalopathy by one year of age associated with global developmental delay and hypotonia. All metabolic workup, TMS, GCMS, and MRI brain were normal. EEG at 2.5 months was suggestive of epileptic discharge arising from the left frontal region, evolving into generalized discharges. Whole exome sequencing revealed a heterozygous mutation in the SCN8A gene at exon 16 (p.Val892Ala) suggestive of Early Infantile Epileptic Encephalopathy-13 (EIEE-13). This is a novel mutation in the SCN8A gene which has not been reported previously in the literature.