Sally, CCSVI is a pretty new procedure that is one reason. All doctors doing it are not on the same page, which they are working on. It happens. Remember the first heart transplant, lung, liver, etc.
The first heart transplant person lived only a short time, so over time they get better and better at procedures. All procedures.They all are still learning. The tests are in infant stage, machines are tech savvy. things can look better or worse on machines.
Apparently the fMRI is the best. Yes with the f there. The Doppler is good but tech savvy and the way our bodies are positioned can show flow or no flow just by turning the neck. The Chest vein (Azygous) can't be seen on Doppler.
So the Gold Standard in the Venogram. Stick the wire up to the jugulars and chest veins, and more places, and dye is injected. If blocked then balloon angioplasty. Then do another Venogram to check out the if the veins stayed opened, if not balloon again. There is a lot to it. The procedure can be 45 minutes to mine ..was 3 1/2 hours.
The doctor has to be so well trained in what he is looking at and how to treat, what size balloon or style of balloon. So much to consider, not like getting a tooth pulled, and not like an Appendectomy either. It is a procedure, yes. But normally you get up and away in two hours with a band aid, and can go eat or rest, whatever.
If they don't get it right the person may not see any benefit, or the meds are not right, or not taken by the person. So much to it, it boggles the mind.
Some PWMS just have too much damage, but are happy for better speech, hearing, or vision, or to transfer when they could not, or no pain. Others get lots of energy, balance or can walk, but they all need PT to get those muscles going again, if they haven't used those legs. Some see benefit right away, others a few weeks or months later.
Some see no benefit, maybe all the ducks were not in a row??? All blockages not seen and corrected? It's a real learning curve.
It is so individual, like everything about MS. Does this help?