While pathogenic missense variants in <i>CACNA1A</i>, <i>ATP1A2</i>, and <i>SCN1A</i> can cause FHM or its sporadic form, they explain less than 20% of suspected hemiplegic migraine cases, suggesting the involvement of other genes or genetic variations, potentially including copy number variations (CNVs). This evidence concerns the gene SCN1A and migraine disorder.