@akc Sorry I was super busy lately with school open and my kids being small still means tons of work. Also, I have to work and babysit my symptoms but I did notice that you already talked to Dr. H and he did diagnose you with bilateral compression of the Jugular veins by Styloid and C1. So I thought you have a case going on and onto the next phase for surgery. Since yours were so clear from imaging and doctor noticed it, I thought they were enough to proceed with surgery.
I did quickly take a look at your CTV images and you have a textbook Vascular Eagle Syndrome with IJV compressions by C1 and Styloid. Your left IJV is the dominant one and is severely compressed by C1 and Styloid and would need a styloid removal and shaving of the C1 to fully decompress it. The right side is smaller and connects to a smaller transverse sinus so opening it won’t drain much but you definitely need the left side operation since it is draining most of your brain fluids.
I also noticed you have bit larger Arachnoid granulations in your Transverse sinuses. You only need to worry if the left one gets too large to block the dominant left TS. You just need to monitor that for now.
Here you can see that the C1 & Styloid compression on the left IJV and C1 compression on right IJV.
Left IJV (light blue arrow) compression by C1 (blue arrow) & Styloid (red arrow).
Right IJV (light blue arrow) compression by C1 (blue arrow) & Styloid (red arrow).
Your Collaterals (red circled veins) and Suboccipital Cavernous Sinus (SCS) (light blue arrows) are dilated because of the compression of the IJVs and blood is being rerouted to them as @elijah has pointed out. Once the IJVs are decompressed they shrink back a bit in most cases
You have dominant left transverse sinus (TS) (red arrows) and smaller almost hypoplastic right transverse sinus (red arrow). You also have Arachnoid granulations in your Transverse sinuses ( blue arrows) although smaller ones are nothing to worry about, the bigger ones pose a problem of blocking the sinus. Yours are moderate in size. Since left TS is the dominant, you need to monitor it so it does not get larger to occlude the vein.
That is all I can see in your CTV. I have not looked into your MRIs. I think you need to address your left side C1 & Styloid compression (both not only styloid). Wishing you all the best.