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A new study suggests that people with multiple sclerosis are more likely to have a narrowing of the veins that restrict normal outflow of blood from the brain than those without the condition.

But the study's authors also say their findings raise question about whether the vein condition is a result of the MS or a cause of it.

The study in published in the journal Neurology and was conducted by scientists at the University of Buffalo. The data is similar to that released from the university in February, 2010.

The researchers performed ultrasound tests on the head and neck veins of nearly 500 people. Most of those -- 289 -- had MS, while 21 had had at least one initial neurological attack of what could be MS, a condition called CIS (Clinically Isolated Syndrome). Another 26 had other neurological diseases while 163 of those studied were fully healthy.

The study's lead researcher, neurologist Dr. Robert Zivadinov, said 62 per cent of MS patients met the criteria for CCSVI. As well, 46 per cent in those with other neurological diseases also had the condition, as did 42 per cent in those with CIS.

As well, 25 per cent of the healthy patients, -- some of whom were family members of those with MS -- met the criteria for CCSVI.

CCSVI, or chronic cerebrospinal venous insufficiency, is a term coined by Dr. Paolo Zamboni, a vascular surgeon in Italy to describe a narrowing of the veins in the neck and chest that restrict normal blood flow out from the brain. He has reported finding the condition in over 90 per cent of patients with MS.

Zamboni established five ultrasound criteria for the definition of CCSVI and says patients with two of the five criteria meet the standard for having the condition.

When the Buffalo researchers in this latest study looked at all the cases that had at least one of the five criteria for CCSVI, 81 per cent of those with MS cases had vein narrowing. Signs of CCSVI were found in 76 per cent of those with CIS, in 65 per cent of patients with other neurological diseases and in 55 per cent of healthy controls.

Zivadinov said in a press release that the findings "are consistent with increased prevalence of CCSVI in MS, but substantially lower than the sensitivity and specificity rates in MS reported originally by the Italian investigators."

Zivadinov was attending the annual meeting of the American Academy of Neurology in Honolulu and was not available for an interview.

The study also found the highest prevalence of CCSVI in patients with relapsing primary-progressive MS (89.4 per cent), followed by non-relapsing secondary-progressive MS. Slightly less than half -- 49.2 per cent – of those with relapsing-remitting MS, the most common form of the disease, had CCSVI.

This "suggests that CCSVI may be a consequence rather than a cause of MS," Dr. Bianca Weinstock Guttman, a co-author of the study, said in a University of Buffalo news release.

"An increase prevalence in progressives as compared to relapsing disease leaves open the possibility that CCSVI may be playing a contributory role in or be a consequence of the disease or may be age related," wrote authors Dr. Robert Fox and Dr. Alex Rae Grant in an accompanying editorial.

They cautioned patients against seeing treatment unless it is part of a formal study. Given the uncertainties of the relationship between CCSVI and MS and the potential risks of intervention, they said balloon venoplasty should be restricted to "a blinded, controlled clinical trial."

A sub-analysis of 10 children with MS who were part of the Buffalo study found half had CCSVI.

"Although the sample size was too small to draw any firm conclusions, these results suggest that CCSVI is also present in children and is not the result of aging," said Dr. Ann Yeh, an assistant professor of neurology at the University of Buffalo.

Other smaller studies on the hotly debated condition were presented at the AAN meeting, including a study from Calgary that used MRI of the neck, also called an MRV. Researchers tested 67 patients and report finding vein abnormalities in 20 per cent of those with MS and 20 per cent of those without MS.

"This first independent Canadian MRV study confirms neck vein abnormalities are infrequent and independent of the diagnosis of MS," wrote Dr. Katayoun Alikhani a neurologist with the University of Calgary.

However the Buffalo research group, which also tested the scans as a diagnostic tool, reports in their study that "MRV has limited value for diagnosis of CCSVI."