Folks. I’m on the verge about becoming partially sceptical about the compressed IJV at C1 theory. Not in general, but for certain cases.
Logically thinking, if the area/flow capacity of the compressed IJV at the C1 level is not as bad as to make it narrower than the most narrow “bottleneck” (jugular foramen), then it shouldn’t impact the venous outflow that much EXCEPT in cases when it becomes more compressed due to certain neck movements (also including the styloid process), nearby muscle compressions caused by posture, muscle tension, stress, and similar cases.
So if one gets a CTA/V in the supine position, while feeling the symptoms, but then it becomes clear that the IJV flow capacity at the C1 level is still greater than through the jugular foramen, it would be safe to conclude that compression at the C1 level isn’t the major and first-line cause?
Which means, full catheter venography with pressure gradients is necessary to even conclude that there are any issues with the IJVs?..
I can see your point…it’s something to consider I guess. From personal experience my worst side was considerably compressed by the styloid, more than it would have been by the jugular foramen. But is definitely something those looking into surgery should perhaps question with their surgeon, good point.
I think someone (not me) with a in depth understanding of fluid dynamics would probably understand this best and while your point definitely seems intuitive I do wonder if compression at the c1 level, even if it’s bigger than the volume above it, still causes a backup.
If you had a long rubber pipe where at the top it was 1 inch in diameter and at the bottom 1 as well but in between those two points it’s 1.5 and then you squeeze the middle of it to match 1 inch, I can still see how it would affect the upstream pressure even though it’s the same size.
Basically, because it’s all a closed loop system with the pressure are internalized, as soon as another point is compressed it means that the fluid that usually went through there is now displaced, even though it matches the upstream compression size.
I have no idea if what I just said makes any sense or what I am actually talking about, but I enjoyed writing this reply so gonna just hit send now anyways.
Yes i think this makes sense Elijah. Its all connected, and ‘classical’ mechanics - e.g. you can get additive effects. Two partial blocks will contribute to each other across the whole fluid system. I agree @vdm that further evaluation with gradient measurements is of course an important tool.
I think there is also an element of dominant jugular vs non dominant here
I think your example is extremely well articulated and visually very simple to imagine!
Thinking about it, I would assume there is some increased back pressure due to the fluid vortexes (I can’t remember, I think I even googled for this exact fluid dynamics effect long time ago when discussing some related things with @KoolDude (I hope you are feeling better by now, KoolDude!)) going from wider area, then hitting the narrower area and some of it bouncing back.
But a) does it reach equilibrium eventually with input pressure (and volume) equal to output pressure (and volume), or does it remains acting like a constant pressure reductor, and b) is it significant backpressure (1%? 10%? Linear? Logarithmic?)
I just remembered there is such a thing like a Tesla valve visually demonstrating how various fluid flow redirections may totally obstruct fluid flow (one way) while the path of full input capacity still exists at every single point, with some places having even larger area at that particular plane. So theoretically, the back pressure caused by “two bulging areas” between the ends of the hose and the compressed spot in the middle of the hose, might be a really significant obstruction (depending on how exactly they affect the fluid flow path in the particular patient’s case)…
I’m just wondering, if in the Tesla valve above we remove the solid pieces splitting the flow into two in each segment, would it still partially reduce the pressure in the “restricted” direction?
Well for me my own experience was just looking at JV compression/narrowing on imaging and seeing which bones are causing the compression. In my case that included C1 and styloid. So getting C1 trimmed and styloid removed to lesson compression made sense for me. My JVs have widened as a result.
Medics have never really given me as much understanding of fluid flow pressures as I would like and radiology reports provide scant details. I agree Venogram can be helpful but sparse reports on them can lessen diagnostic value. D
