I'm not sure if this is really something relating to this area, but I was hoping someone here might be able to answer a question or two.

I have chronic muscle spasms in my neck and shoulder, but they usually don't bother me a lot. A few months ago I had a rotator cuff injury, and it seems to just keep getting worse. My doctor just told me to use lidoderm patches and ibuprofen for the pain, but it doesn't seem to affect it at all.

I do stretching exercises to help with spasms in my arms, legs and back. Does anyone know if it's better to try to do them with my shoulder when it's damaged, or is it better to try not to force more movement in it now? My range of motion is getting worse, I'm lucky if I can move it 30 degrees forward, not at all backwards, and about 15 degrees to the side.

Your description makes me think of thoracic outlet syndrome {TOS}.
I'm not up on all the MS symptoms so i don't know if that is a usual thing with MS or not.
But I do have TOS from multiple RSI injures and that's why the thought jumped out at me.
Any repetitive work, car accident , sport injuries?
Often previous arm,neck, shoulder injuries can be a precursor to TOS.
We do have a TOS forum here if you would like to read more about it-
http://neurotalk.psychcentral.com/forum24.html

Thanks, I'll read up on that too. I know my neck problems started with a car accident that tore the ligaments there. The shoulder started after I tripped and caught myself by grabbing a wall. It felt like a knife going up the bone from the elbow to the shoulder and it hasn't been normal since.

ahh yes could be something related to it then.
here's the TOS useful sticky - full of info http://neurotalk.psychcentral.com/thread84.html