They don't care if you take your business elsewhere. Sad, but true. It's difficult, political and one of those situations that calls for diplomacy and a stiff backbone. Valerie, if you feel you owe it to the neurologist to give it one more try, I like the suggestion of speaking to the office/practice manager (better for you if there is a practice manager), but be prepared with a very specific list of concerns, specific questions, the person from whom you expect to hear by telephone or in a face-to-face, and a deadline. Demand (nicely) to fax/email the list so there will be no misunderstandings. The response will tell you what you need to do.
I wish you well and more than that, I wish a sustained recovery for Diamond.