@snowmass The reason that a lot of doctors will not treat spine issues at C3 and above is because of possible risk to the nerves that control life support, in servicing your heart and lungs. This would also be a reason not to inject upper levels of the C spine. I had an injection just below C5/C6 and the anesthesiologist who did that said no one should be injecting the C spine above that level for patient safety.

You do need to find a specialist who does work at these levels just below the skull. The spine surgeon at Mayo who does regenerative spinal cord research for spinal cord injury is Dr. Bydon. I'm not sure what surgeons would be experts at C1 and C2 levels. You may not be a spinal cord injury patient. He has had some success with stem cells, but that doesn't help all patients, and he is researching this.
https://www.mayoclinic.org/biographies/bydon-mohamad-m-d/bio-20147826