I would guess the other way, as Zamboni explicitly tested people who were taking steroids for a relapse, and they also failed the doppler tests. ie to me, steroids did not appear to make actual flow changes.
I have been meaning to post something RE steroids and CCSVI for some time now. A few years back I did a thread regarding the BBB & steroids, as at the time, I found numerous articles that implied/showed steroids worked so well for MS because they were VERY effective at shutting down the BBB's integrity issues.
I was thinking, that maybe, if you can, taking a shot of steroids at the time of the vascular operation, this would shut down the BBB's leakage in a quick manual way, as opposed to waiting for it to naturally heal, now that the causal factor (CCSVI) has been fixed. Which I am guessing/proposing is the reason that Zamboni had patients take between 4 hrs and 4 days to recover from a relapse; ie it took different lengths of time for their tight junctions to "tighten up".
Maybe this is also why PP & SP patients take longer to recover, their BBB has more long lasting damage, and thus will not "close back up" as naturally and quickly as hoped.
The other "link" with steroids and CCSVI i'd like to make (stretching), is the research that was done that found long term, pulsed steroids gave progressive patients HUGE reductions in EDSS's. I'm going to go out on a limb and propose that the steroids shut down the leaky BBB, and the CCSVI took longer to re-instate the "leakiness" (sorry for the technical terms...).
Please note all the "maybe's" and "possiblies" and "think's" in the above post.