Chronic cerebrospinal venous insufficiency or CCSVI is the name Italian Dr. Paolo Zamboni gave to a condition he described in 2008. Zamboni said CCSVI occurs when narrowed or blocked veins in the neck or chest interferes with blood flowing from the brain.

Small studies on people with MS suggest the blockages lead to different patterns of blood flow back to the heart. Blood leaves the central nervous system differently than normal. For example, it may flow more slowly, leading to swelling, or may move backwards or "reflux" into the brain.

In February 2010, a preliminary study by Dr. Robert Zivadinov of the neuroimaging analysis centre in Buffalo, N.Y., showed about 55 per cent of patients with multiple sclerosis and up to a quarter of healthy people studied show narrowing of their neck veins that may be a risk factor in the neurological disorder.

In April 2011, Zivadinov's larger study cast doubt on vein narrowing as a cause of MS. The study of 499 people included 289 people with MS. Half of the subjects with MS, 56 per cent, met the criteria for CCSVI. Since the people with more progressive MS were most likely to have vein blockages, the researchers speculated the condition may actually be a result of MS, not a cause.

Canadian Dr. Joseph Hewett has been doing neck vein angioplasty for about 15 years. He now performs balloon angioplasty on people with MS in southern California. He says Zivadinov's latest study has flaws and that he will continue doing the surgery until there's a "gold standard" study.

Different tests are used to diagnose CCSVI. Doppler ultrasound of the neck and skull may show if blood is refluxing. Venography, which involves injecting a dye into the veins to watch blood flow and possible stenosis in the azygous vein in the chest and the two internal jugular veins, is also used.

Doctors may also turn to more sophisticated tests using magnetic resonance venography and magnetic resonance imaging to look for abnormalities. Researchers are still investigating the best protocols and tests to use. There's been a debate over developing standards to diagnose the condition.

Treating the condition is more controversial. Zamboni's angioplasty-like procedure involves a small incision in the groin to insert a catheter into the blocked vein that is opened with a small balloon. In his small study, most of the 65 patients who had the procedure had fewer MS attacks and brain lesions, although the improvement was temporary for about half. A U.S. clinic at Stanford University in California that was doing Zamboni's procedure stopped after a metal stent put into a patient's vein moved into his heart.

On Oct. 19, 2010, a St. Catharines, Ont., man died of complications months after undergoing the treatment in Costa Rica. Mahir Mostic, 35, had a mesh stent inserted into a vein in his neck in June. He returned to Costa Rica for treatment in October after a blood clot developed around the stent. He died a day after doctors tried to dissolve the clot.

In April 2011, Maralyn Clarke, 56, of Calgary died soon after the surgery in California.

There are some clinics in Canada that offer testing for CCSVI but not the procedure itself. The surgery is available in several countries, including the U.S., India, Mexico, Costa Rica, Poland, Romania, Bulgaria and Serbia.

Since word of Zamboni's work became public, Canadians with MS have been clamouring for the procedure and have travelled to various countries to seek it.

A review article in the Annals of Neurology challenged the role of CCSVI in MS and discouraged people with MS from having invasive procedures until the benefits are demonstrated more conclusively.

The findings need to be repeated in more patients and controls with consistent MRI protocols, the reviewers concluded. Further studies also need to be blinded, that is, researchers can't know which subjects have the disease and which don't, to help prevent bias. Given ethical concerns, MS patients who have the treatment are told to continue taking their disease modifying medications, which makes it harder to determine the effectiveness of the surgical treatment.

In June 2011, the federal government reversed its position on paying for early-stage clinical trials into using angioplasty to unblock veins in those with MS.

Previously, Health Canada refused to fund a large-scale trial of the procedure saying there was no scientific evidence yet that CCSVI works, is safe or that there is an established link between blocked veins and MS.

In June 2010, the MS Society of Canada and the U.S. National MS Society announced that they had committed $2.4 million to study CCSVI and its relationship with MS.

Several provinces and territories have also announced research projects into CCSVI.