Multiple sclerosis (sclerosis multiplex--SM) is a chronic nervous sytem disease, which through formation of demyenilisation focus in the central nervous system leads to deterioration of its various functions. In the consequence it may cause invalidity of patient. Etiology of this disease is still unknown. In this article authors describe theory of Chronic Cerebrospinal Venous Insufficiency as a possible cause of multiple sclerosis and methods of treatment of this pathology, with all doubts and controversies connected with this method. Autors also present an experimental treatment of Chronic Cerebrospinal Venous Insufficiency in patients with multiple sclerosis, which is being performed as a scientific program to evaluate neurological outcomes of endovasculat treatment of CCSVI.