@ajp2019 I think calling Mayo at Jacksonville would be a great first step. They can advise which doctors have interests in treating Bow Hunter's syndrome. Doppler imaging is an ultrasound where there put a wand in some gel on your skin and pick up images of blood circulation. The red or blue color indicates direction of blood flow and if it is an artery or vein. That color coding is used for this type of imaging all of the body. I've had Doppler imaging done on myself before. This link about the Atlas (C1) and Axis (C2) has a section that talks about Bow Hunter's Syndrome if you scroll it down. It is a technical article written by a physical therapist.
- Do you really have atlantoaxial and craniocervical instability? A critical view on the overdiagnosis of AAI/CCI https://mskneurology.com/do-you-really-have-atlantoaxial-and-craniocervical-instability/

I hope you'll share your status with us after you are evaluated and how you are doing. My C1 & C2 have been prone to rotating on their own from muscle spasms, but that was before my spine surgery and I also have thoracic outlet syndrome putting uneven pressure on my spine with extra tight muscles on one side which pulls harder on one side of my spine. I still can have a spasm that will cause some rotation, but not to the same degree as before. I make sure that I don't turn my head to the side while I'm sleeping.