[Rani]

Six months ago I had 2 shots of cortisone in my shoulder & back for bursitis & tendonitis. Within 2 days my arm and shoulder began to loose its strength. Within 2 weeks I was totally atrophied from my deltoid to my bicep and forearm.
I have been to five docs all scratching their heads and MRIs EMGs and still no answers. I am starting to recover and the deltoid is coming back to life. 2 docs feel that a motor nerve could have been hit with the needle. Has anyone ever heard of this happening from an injection. If not, what could have happened.
All major neurological muscular disorders have been ruled out.

[rumpled]

While cortisone is known for its anti-inflammatory properties, it also has a side effect of um, muscle weakness. Most doctors feel (incorrectly IMHO) that the only effect of a local steroid is a temporary rise in blood sugar. They feel ihnalers do not cause steroid side effects either.
I had Cushing's syndrome (the disease form) which is when the body makes too much of its own steroids. My muscles went to crud and my steroid levels - equivalent to hydrocortisone - were not even that high. I know others that had super high levels and recovered fine and others that had low levels and were damaged. There is no correlation between the levels and the damage - it all just depends on the luck (?) of the draw. Some people's bodies cannot handle steroids at all while others handle it in stride. There is no way to tell who will or will not handle them - except by who gets side effects by steroids at low levels will generally be more damaged in the long run from what we have seen among friends.
Steroids have a biologic half life. Steroid myopathy is supposed to be temporary. I hope what your doctors and you take away from this is avoidance of steroids - and be grateful you were not given a long lasting one.