@Dontgiveup I think when they do the catheter angiogram/venogram, they can quantify how much compression is coming from the Styloid or C1 or both by asking you to turn your head right, left, front and back. It can be that your Jugular compression might even be worse when the neck is moved to different positions since you have cervical instability. So ask them to do DYNAMIC Angiogram/Venogram if they do not already plan it. I also highly recommend you try SOFT NECK COLLAR/CERVICAL COLLAR. I have seen huge improvement and it is comfortable to wear. In your case, it might even give a temporary relief of the cervical instability issue along with the ease of ES symptoms. I am not advocating any brand, but I found this brand (Velpeau Neck Brace -Foam Cervical Collar) to be both affordable and comfortable to wear.