A national clinical trial to test a controversial vein-opening procedure in people with multiple sclerosis has medical and ethical approvals.

Health Minister Leona Aglukkaq announced the collaboration between the federal government, British Columbia, Quebec and the MS Society of Canada on Friday.

"This pan-Canadian controlled study will allow us to monitor MS patients over a two-year period and obtain scientific evidence on the safety and efficacy of the chronic cerebro-spinal venous insufficiency (CCSVI) procedure in the long term," Dr. Anthony Traboulsee, medical director of the UBC Hospital MS Clinic, said in a release.

CCSVI is a hypothesis put forward by Italian vascular surgeon Dr. Paolo Zamboni. He suspects that narrowed neck veins create a backup of blood that can lead to lesions in the brain and inflammation.

CCSVI treatments offered abroad involve ballooning and stents to unblock veins from the brain.

Traboulsee and his collaborators received ethics approval from institutions in Vancouver and Montreal to conduct a clinical trial. Two others sites, one in Winnipeg and one in Québec City, will be added pending on ethics approval.

Patients in B.C. and Quebec will be recruited starting Nov. 1, the Canadian Institutes of Health Research said.

"Only residents of provinces where the trial will take place are eligible," CIHR said on its website.

"Participants will have to live within a safe travel distance of a trial site, as the procedure involves surgical intervention and frequent follow up visits."

Patients will receive the CCSVI procedure either at the beginning or end of their participation in the study, a spokesperson for the institute said.

Seven studies are underway in North America, sponsored by the MS Society of Canada and its U.S. counterpart, that are looking at whether vein abnormalities and MS are linked, as Zamboni proposed.

Saskatchewan and Yukon are sending patients to the U.S. for a clinical trial involving ballooning or a placebo.

In June, an observational study of people in Newfoundland and Labrador who travelled abroad for the treatment found no measurable benefit.