Remember that in CCSVI we are discussing intraluminal abnormalities, such as valves or septums or webs, not stenosis of the veins themselves. The Cleveland Clinic autopsy study found the same percentage of vein stenoses or narrowing in MS patients as in healthy controls. Any theories such as self-contorting of veins to maintain pressure or that the lowered perfusion of MS means lowered volume of flow leaving the brain means narrowed veins are not consistent with the Cleveland Clinic autopsy study that showed equal degrees of vein wall stenosis in healthy controls and MS patients. What the autopsy study did show was a much higher percentage of intraluminal abnormalities in MS patients.
I don't view the Cleveland study with the same awe as you. With all the abnormalities found, unexpected in both MS and controls, and a very small sample, it really doesn't say much more than there might be something more to study. I could not draw any conclusions from it. The stats and criteria for categorizing the findings are purely observational and don't have much statistical power. It is difficult to say what is normal, what is natural variation, and what is pathological. I would say, "that's interesting." Then I would wait for follow up studies.
It is not evidence of anything, except the strangeness and variation of the IJV in humans.
But, you can't have your cake and eat it. If this is a study you would weigh highly, than it pokes some holes in the ccsvi theory as well, along with chronic inflammation affecting the jugulars. One "fact" would be the claim from Zamboni for constant reflux in the IJV in 71% of MS and 0% of controls. If that were the case, the Cleveland study would have supported some vascular remodeling consistent with Glagov's phenomenon.
That, or it is what it is and not to be read into so much.