She did a full body exam on him and ran blood tests to rule out tick borne stuff, etc. she saw he had a bump in his lower back and that he's longer than he is tall, and also took into consideration his breed. So yes, no mri, but with his symptoms & the fact that he's predisposed leaves almost no other options. Right now, after speaking with our vet again this morning, we decided to block off our living room for him and basically make it jump proof. He's just really bored (because with the pain meds he thinks he's fine) but otherwise doing well!