SCN1A and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy: The dissociation of these phenotypes may have several explanations: The pain threshold may be higher in Dravet syndrome because of a deficiency of peripheral Scn1a/Nav1.1 channels maintaining sensory nerve excitation (53), whereas FHM3-linked Scn1a gain-of-function mutations might reduce this threshold (54) and intensify headache sensation.