The U.S. Food and Drug Administration issued a warning today about a controversial and experimental vein procedure for people with multiple sclerosis.

The regulator warned health-care professionals and patients that injuries and death have been associated with use of the procedure for what is known as chronic cerebro-spinal venous insufficiency (CCSVI).

Dr. Paolo Zamboni's theory is that narrowed neck veins create a backup of blood that can lead to lesions in the brain and inflammation that can be treated by opening up veins. ((Nathan Denette/Canadian Press))

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

The treatment, which involves opening blocked neck veins with balloons, is not offered in Canada.

The idea that the condition might be linked to MS, a progressive neurological disease, has divided the medical community.

Some patients have travelled around the world to seek treatment, even though it hasn't been approved by medical bodies.

In its warning, the FDA said it received reports of one patient who died from bleeding in the brain and one patient who suffered paralysis from a stroke after the treatment.

Other serious complications reported include:

• Stents migrating from a vein to another part of the body, including the heart.
• Injuries to veins.
• Blood clots in the jugular vein or the brain.
• Cranial nerve damage.
• Abdominal bleeding.

The frequency of such complications is unknown, the FDA said.

"I've always said that we'll make decisions about this treatment based on the best scientific advice available," Health Minister Leona Aglukkaq said in an email.

"Before our government will give the green light to a limited clinical trial here in Canada, the proposed trial would need to receive all necessary ethical and medical approvals. As Minister of Health, when it comes to clinical issues, I rely on advice from doctors and scientists who are continually monitoring the latest research, and make recommendations in the best interests of patient health and safety."

Following the U.S. announcement, Health Canada officials said they are going ahead with a proposed clinical trial of CCSVI. The trial is now undergoing an ethics review. Until it clears all approvals, there won't be applications received from interested patients, a department spokesperson said.

CBC News has reported at least two Canadians have died from complications after having the treatment abroad.

No reliable evidence

"Because there is no reliable evidence from controlled clinical trials that this procedure is effective in treating MS, FDA encourages rigorously conducted, properly targeted research to evaluate the relationship between CCSVI and MS," said Dr. William Maisel, chief scientist and deputy director for science in the FDA's Center for Devices and Radiological Health.

"Patients are encouraged to discuss the potential risks and benefits of this procedure with a neurologist or other physician who is familiar with MS and CCSVI, including the CCSVI procedures and their outcomes," Maisel said in a release.

The federal and provincial governments have been under pressure to fund the procedure.

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 plans to send patients to Albany, N.Y., for a clinical trial involving ballooning or a placebo.