CCSVI exists, and is easier to see and diagnose using intravascular ultrasound.
"IVUS assessment of azygos and IJ veins showed a higher rate of venous abnormalities than venography. IVUS provides a diagnostic advantage over conventional venography in detecting extracranial venous abnormalities indicative of chronic cerebrospinal venous insufficiency."


Comparison of Intravascular Ultrasound with Conventional Venography for Detection of...
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Journal of Vascular and Interventional Radiology, Volume null, Issue null, Pages null, null, Authors:Yuval Karmon, MD; Robert Zivadinov, MD, PhD; Bianca Weinstock-Guttman, MD; Karen Marr, RVT, RDMS; Vesela Valnarov, MD, RVT, ARDMS, RPVI; Kresimir Dolic, MD; Cheryl L. Kennedy, LMSW, MPH; David Hojnac...