** I am not an expert but here is my take **
I have read some paper relating to genes and MS. Most of the current research assume the culprit is a malfunctioning immune system and then try to find the culprit genes (within the known genes that control the immune system). If CCSVI is true then you won't find anything wrong in the immune system, since nothing is inherently wrong there. So, as long as the starting point is incorrect, the issue likely to escape (remember starting point & local minimas, 1eye)
The second part of the problem is that difference between genes may or may NOT mean anything. For example, it is normal for genes to undergo mutation. Part of normal process. But every mutated gene need not cause a specific issue.
But yes, the current issue in doing exhaustive gene scanning is probably time. And if technology improves (like chips doing this task) then complete scanning might become routine ...
Some exciting times ahead ...
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die and a new generation grows up that is familiar with it
- Max Planck