Jim, sorry had to dash out and didn't finish what I was going to say!
When you say you had a post op MRI are you sure it wasn't a CT scan?
Also was it done after everything was hooked up and in place meaning stimulators switched on though obviously switched off by medtronics rep for the MRI?
I was one of the first to have DBS with my neurosurgeon and he's not sure but seems to think that in the process of connecting the stimulators the electrode may have migrated a fraction but enough to cause the problems that it did.
I vaguely remember (correct me if I'm wrong) that you were happy initially which means it could well be a programming issue.
Either way I still think a new MRI would give you and Dr a better idea.
Lee