Lissencephaly caused by LIS1 or DCX mutation frequently results in West syndrome, while lissencephaly due to ARX mutation is associated with the most severe form of epilepsy but never results in West syndrome nor infantile spasms.
However, Lis1 and Dex mutations that appear to affect the cytoskeleton and perhaps intracellular protein trafficking are frequently associated with infantile spasms and epilepsy.