A study published online will add to the debate raging among the multiple sclerosis patient and research communities. The paper, published in the Annals of Neurology, says researchers found no evidence that blockages in veins play a significant role in MS.

Doctors from the U.K. and Germany said they performed extracranial and transcranial venous ultrasounds of 76 people -- 56 with MS and 20 healthy controls. Researchers say that only one patient showed abnormal blood flow in the jugular and vertebral veins.

"Our results challenge the hypothesis that cerebral venous congestion plays a significant role in the pathogenesis of MS," write Dr. Klaus Schmierer, a neurologist at Barts and The London NHS Trust, and colleagues.

The finding runs counter to that reported by Italian vascular surgeon Dr. Paolo Zamboni and a research team at the University of Ferrara. They reported finding impaired blood drainage in over 90 per cent of patients with MS.

A second study at the University of Buffalo found more than 50 per cent of patients had blocked or narrowed veins that impaired blood flow out of the brain -- a condition Zamboni has dubbed CCSVI, or "chronic cerebro-spinal venous insufficiency."

However some scientists say the ultrasound test requires specialized training.

Canadian vascular surgeon Dr. Sandy McDonald has been testing MS patients as part of an ongoing study, using a technician trained by the Italian research team. He reports finding venous abnormalities in over 90 per cent of those with MS.

Other doctors say venograms are the gold standard for CCSVI testing. Dye is injected into the veins to see possible blockages and improper blood flow.

Dr. Tariq Sinan in Egypt reports in unpublished data that his group is finding 84 per cent of MS patients have venous abnormalities compared to 7 per cent of healthy controls using venograms.

"This paper is the only paper with such result that is completely opposite to all published papers on the subject that show link between CCSVI and MS. It needs to be validated with more studies and a bigger number of patients," said Sinan

The U.S. and Canadian MS Societies have awarded $2.4 million in research grants to better study the theory that blocked veins may be linked to symptoms of MS. Four Canadian universities and three American centres will begin research later this year.