In Benign idiopathic neonatal seizures the cause is not known (this is what the word ""idiopathic"" means). In Benign familial neonatal seizures and Benign familial neonatal-infantile seizures, there is a "genetic mutation," which means a change in the genes that an infant gets from their parents. These disorders are inherited (they "run in the family"). This is what the word ""familial"" means.