Frank,
My employer is 'unique' in that, they employ several people with disabilities. When I was diagnosed, first thing I did after calling my parents was call my manager at work and tell her. She told me, "Laura, if you need 6 more months of recovery time, take them".
They are well aware of what MS can do (relapses) and yes, they will accommodate this. In fact, I knew at least 1 person at work who also has MS before I found out that I have MS.
When I told my neurologist where I work, his words were "Never quit that job". Since finding out they're covering my drugs 100% now, and they've outright paid certain visits that I would have had to otherwise pay myself, I've seen what the company can do for it's employees. November will be my 7th year 'anniversary' working there, however I have been out since February of 07, as I mentioned earlier.

Might affect my 'overall' tenure a bit!
I work at a desk, typing. My MS symptoms I experience have been 100% sensory/vision (the vision is blurry vision at range, looking at a PC monitor, I don't have this). The only symptom I had that doesn't fall into the sensory/vision category entirely was vertigo, and it is possible that I had BPPV (I have not experienced vertigo since last year), or another ear infection that could have caused this at the time.
So I've been extremely fortunate in that, I can still perform my job as I did before. Sensory symptoms are not fun (lots of burning and tingling at times, pain aspect there), but they're manageable now. I don't experience fatigue like some do. So I imagine I can perform my job as I did before. I miss the challenge!
Edit: My job itself was really stress free for me. I had the freedom to get up, move around, bounce ideas off coworkers. I wasn't talking to people on the phone, I was answering emails from clients (for a bank here in Canada), so I really enjoyed working.