I would like to point out that you can have adnormal hereditary inflammation despite having a normal ECR tests. Note: I have CNS vasculitis, a diseaserelated to inflammation of the blood vessel but ECR test came out normal.

Concerning your dog, if it was a human, I would check for systematic lupus-type diseases. An MRI isn't that great for this. A full panel check or an angiogram. This is because the MRI isn't high enough resolution. In an angiogram, a scope is inserted into a vessel, then dye is used to help take pictures of the problem area. Also, watch your dog carefully if your giving that much predisone. Predisone can cause bloating, leaches calcium out of bones, and skin rashes. You'll also want to gradually reduce dosage instead ofstopping immediately.

I hope they find out what's wrong. Good luck.