What Causes Dizziness, Joint Pain And Nausea With A History Of Chiari Malformation?

Hi, my wife (39yo) has been Dr.ing for years without figuring out what is wrong with her. I feel like we re close to figuring something out, but I think she needs an impartial opinion. For years, she has been weak and shaky, nauseated often and has had pain in joints and ribs which has been treated successfully sometimes with a prednisone taper. She spends most of her time in bed or in a recliner Lately the pain in the ribs (front and back) has been pretty steady and her upper legs have been achy and sore to the point that she can t do anything and is sensitive to the touch. The other thing that has come up recently is that she has fainted a minute or two after getting up and moving around. She has other problems but all of these seem connected and come and go somewhat cyclically together. She was previously treated for Arnold Chiari syndrome and currently takes Cymbalta, Neurontin, a small amount of time release morphine for some of these pains. She is currently wearing a heart monitor to see if that is related to her fainting but she has fainted with it on and hasn t had any calls for concern from the monitor company. Any thoughts?