i go through periods ot time waking with tremendous cramps in my legs. i am going through such a period now. Taking magnesium helps, as well as gatoraide. I dont know if it has anything to do with involvement of motor nerves in some PN or if it is something like the double crush phenomena where because your nerves in one area are damaged nerves in other areas can be damaged more easily and to a greater degree than would be possible for people without PN or if it has nothing to do with PN at all.