Is there a specialty hospital near you, or a university vet school? I've decided a long time ago that anything that requires more indepth diagnosis, that I'm going to go to a specialist. They are expensive but have paid off greatly.
If you're in NJ, we have Oradell in the North, Red Bank in the east, U of Penn in the southwest, Veterinary Specialist and C.A.R.E.S in the west. Boy am I lucky.