SCN8A and infantile epilepsy syndrome: As a patient grows, the function of Nav1.2 was gradually replaced by Nav1.6 encoded by SCN8A. At that time, the SCN2A gene is predominantly expressed in cerebellar granule cells and unmyelinated nerve fibers (Vacher et al., 2008), which explains why our patient had neonatal or infantile epilepsy early in life and then developed ataxia later.