Wait what polarity reversed ? Current goes from A to B, so it doesn't quite matter ! So side B from the skull is negative and A is positive, unless you reverse

Wait what polarity reversed ? Current goes from A to B, so it doesn't quite matter ! So side B from the skull is negative and A is positive, unless you reverse it, then it's reversed ... But regardless one side will always be "reversed"... So the question is rather where you want the current to go exactly, but if "reversing" the polarity is bad, it's safe to say EVERYTHING is bad. (Unless you don't mind destroying a part of the brain to get to another part.)