I'm not a doctor so I've decided to provide you with the simplest definition I could find of CCSVI, from Wikipedia:
"Chronic cerebro-spinal venous insufficiency (CCSVI) is a term used to describe compromised flow of blood in the veins draining the central nervous system. It has been hypothesized to play a role in the cause of multiple sclerosis (MS). This hypothesis was first put forth by Paolo Zamboni in 2008. ."
Generally, the veins in the neck are blocked causing block to back-up into the brain, leaving excess iron. By opening the neck veins up, through a surgry similar to antiplasty, the body is able to restore regular blood flow. In many cases this has caused amazing results for MS patients. All you need do is watch the news and nearly every week there is a new "miracle story" of somebody regaining fuction after having their veins re-opened through the "liberation treatment."
For more information about CCSVI and the Liberation Treatment check out: