Scientists have found MS sufferers are more than twice as likely to have restricted blood flow from their brains, compared to healthy people.
Initial findings from a trial indicated a link between the narrowing of veins in the head and neck and the condition.
The scientists said they were "cautiously optimistic" about the findings.
They found over half of MS patients who took part in the study had narrowing of the extracranial veins, which restricts normal blood flow, compared with 22.4% of healthy controls.
The results emerged from preliminary data of a randomised clinical study at the University at Buffalo in the US.
They are based on the first 500 participants in the Combined Transcranial and Extracranial Venous Doppler Evaluation (CTEVD) study, which began last April.
Complete data will be presented at the American Academy of Neurology meeting in April.
Robert Zivadinov, associate professor of neurology and principal investigator on the study, said he was "cautiously optimistic and excited" about the results.
He said: "The data encourage us to continue on the same course.
"They show that narrowing of the extracranial veins, at the very least, is an important association in multiple sclerosis.
"We will know more when the MRI and other data collected in the CTEVD study are available."
University at Buffalo
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