@goldenretriever - Welcome to our forum! Your symptoms definitely are those seen w/ styloid elongation/stylohyoid ligament calcification & vascular compression. As @TML said it’s possible you have both jugular & carotid compression happening depending on your head position.
The advantage of a CTA/CTV (besides not using the gadolinium based contrast) is those can be done “dynamically” i.e. w/ your head turned in different directions which can help show what’s being compressed & what’s causing the compression. An MRA/V can’t be done dynamically & as @Jules noted, because MRIs predominantly show soft tissues, they can obscure the bones that are causing or contributing to the problem. Is it possible for you to request that the rheumatologist change the order for your scan from an MRI/MRA to a CTA & CTV?
Here’s a link to a good post about gadolinium contrast, but I have to say not everyone gets a bad reaction to it. It’s just wise to be informed of possible side effects if you’re going to receive it. CT scan contrast is iodine based so it flushes out of the body more readily.
Link to Research Papers: Research Papers - Living with Eagle
And a final link to one of the great posts @Jules wrote regarding ES symptoms - ES Information: Background, Anatomy, Styloid Length, Angulation, Classic and Vascular
I hope this information is helpful. We’ve only had a few members from NZ & some have needed to go to AU to have their surgeries especially when vascular compression is involved.