cidp symtoms

Back in March I began getting symptoms in my feet then travelling up my legs and presently up into my buttocks. I have drop foot in my right foot and I can barely bend those toes yet my left foot works normal. The symptoms have not progressed any farther but the intensity in my legs is to the point I have little endurance and require crutches to walk any distance. I’ve had 2 times HIVG loading doses, the last one just this past week. Why does the disease not migrate up to my upper body after 4 months of suffering in my legs?