I asked Dr. Arata to tell me the percentage of stenosis and he responded that "stenosis" was actually an incorrect description of what was going on.

"Stenosis" means a narrowing of the vein. So, while technically correct, it's not really descriptive of what is going on - at least in my case. There can be other reasons for a narrowing or 'stenosis'.

However, what was going on for me (and for most people with MS) was a malformed valve - the valve has closed and does not open again.
Think of a sphincter muscle or rubber band.
Dr. Arata said that these valves occur every 5~7cm in the veins and some have ceased to work properly.
Note his report on the 'My Experience' page

His treatment is to use the balloon to expand the valve/sphincter muscle till it breaks (think of expanding a rubber band till it breaks.)
His opinion was that once the valve was broken/destroyed, if everything went well for the next 6 months (i.e. no problems in the treated valve area with scarring or clots) then there would be no restenosis and the vein would remain open for the rest of my life. In other words, no further treatment was needed.

I asked about Dr. Hewitt's comments that restenosis was inevitable after 3~5 years but Dr Arata said that in this case, with the repair of a malformed valve, his opinion was that only this singular treatment was all that was needed.

He indicated that my left side jugular vein was almost completely blocked off and the right side jugular vein significantly blocked off - but didn't give me any percentages :-).

There have been studies which suggest that this malformed valve is a result of genetics and therefore present from birth and therefore a cause or precursor/forerunner to MS.
And there have been some recent studies that suggest the malformed valves are a result of MS - i.e. that MS causes the valves to cease to function properly.

Based on my own experience that many of the CCSVI symptoms have been there since I was young, I prefer the genetic theory.

So now I can blame mom & dad for my MS (just kidding guys :-) - but more importantly - we have the tools to correct a genetic defect - and that's pretty special!