JACC - Association Between the Extent Of Extracranial Venous Anomalies and Clinical Severity and Duration of Multiple Sclerosis
http://content.onlinejacc.org/article.aspx?articleid=1383466

"Conclusions
The clinical severity of multiple sclerosis as well as duration of disease seems to be associated with the extent of pathological venous drainage of the central nervous system. To answer the question if CCSVI is only the accompanying secondary process, or the underlying condition of MS, the blinded randomized studies are needed."