What Causes Radial Nerve Palsy With Numbness And Shooting Pain In The Arm?

I had a pain in my shoulder blade after working that has sent me to hospital for mri,xray,ctscan,and emg they said muscle stain and told me to go to therapy. Went to therapy and woke up the next day with wrist drop and numbness in hand and wrist. Then was sent to get an emg and was told radial nerve palsy. Since then I have lost most of the use of my arm and now have constant shooting pains. Doctor today told me he wants another emg and more blood work. He thinks that my immune system is fighting something in the nervous system. HCe also put me on steroids for a month. Any other thoughts or suggestions?