An Italian doctor who contends multiple sclerosis may be caused by blocked veins in the neck defended his research from critics Wednesday but also cautioned that further studies are necessary to prove that the treatment he developed is both safe and effective.

Vascular surgeon Dr. Paolo Zamboni believes that narrowed veins in the neck lead to poor blood drainage from the brain, resulting in a build-up of iron deposits that can damage brain cells.

Zamboni's research on a small number of patients in Italy has found that MS patients are more likely to suffer from this condition, which he calls chronic cerebrospinal venous insufficiency, or CCSVI. Zamboni has dubbed his treatment for CCSVI, a balloon angioplasty, the "liberation treatment."

At a meeting in Toronto attended by neurologists from around the world, Zamboni said his research proves there's a link between MS and CCSVI, but that research into the treatment "is really a work in progress."

While he cautioned thousands of patients who were observing the meeting online that the treatment must still undergo rigorous testing among a much higher number of patients, he urged doctors to consider offering it to patients who were not responding to traditional therapies and whose conditions are deteriorating.

"I invite neurologists to consider to offer this treatment under compassionate grounds," Zamboni said.

At Monday's meeting, scientists from the University of Buffalo presented further research that suggests a strong link between CCSVI and MS.

Using ultrasound and brain scans, the researchers found that between 60 per cent and 90 per cent of patients with MS tested positive for signs of blocked veins, with higher rates among those with more severe forms of the disease.

"Clearly, there is prevalence of CCSVI with ongoing disease, which must be investigated further," said the University of Buffalo's Dr. Robert Zivadinov.

While Dr. Aaron Miller of the National MS Society in the United States called the early findings surrounding CCSVI "exciting and intriguing," he said more research is required to firmly establish the link between blocked neck veins and MS symptoms.

Dr. Andrew Common, an interventional radiologist at Toronto's St. Michael's Hospital, cautioned patients against seeking treatment in a number of foreign clinics that diagnose CCSVI and offer the "liberation treatment" at a cost of thousands of dollars.

"We have to make sure our patients are enrolled in a study that will assess the benefits, the true benefits of the study," Common said.

Some doctors are openly skeptical of the theories.

"There is no evidence that one, this exists at all and two, if it exists that it isn't a result of the disease," said Dr. Robert Lisak, chief neurologist at Wayne State School of Medicine in Detroit.

Lisak said that until CCSVI and the treatment are tested in randomized-controlled trials, "you're talking about testimony, you're not talking about evidence."

About 2.5 million people worldwide have MS, which doctors have long believed is an autoimmune disease in which the immune system attacks the sheath of myelin that covers nerve tissue. The degenerative disease varies in severity and can cause symptoms that range from impaired speech and vision problems to paralysis.

As the debate about CCSVI's role in MS continues, studies are underway in the United States and Europe, with more scheduled to begin in North America in the coming months.

In the meantime, doctors say MS patients should not stop conventional treatments for their disease.

With a report from CTV's medical specialist Avis Favaro and files from The Canadian Press