ATP1A4 and familial hemiplegic migraine: Caution should be taken in view of the recent description of a mutation in ATP1A4 in a family with familial hemiplegic migraine (FHM) [56], suggesting that Na,K-ATPase alpha4 is expressed in the human brain, and, therefore, inhibitors that are able to cross the blood–brain barrier may have significant negative side-effects.