This sounds really unusual to me because I've had the same vertebrae in my neck fused, only not all at once. I had my first fusion procedure at the C5-C6 level, and then about a year and a half later I had a second procedure at the C7-T1 level. The surgeries were performed at 2 different hospitals by 2 different neurosurgeons, and the only complications have been not being able to turn or raise and lower my head like I used to.
If it hasn't happened yet, I'd request an new MRI of your upper spine and neck, something doesn't sound right to me.