A theory that multiple sclerosis is caused by obstruction in the blood vessels that carry blood from the brain back to the heart has been called into question by two recent studies. The theory, which was proposed last year, quickly led to millions of dollars in research pledges for MS, which has long been lacking in new research avenues. But new research published in the Annals of Neurology has undermined the accuracy of the vessel-obstruction theory. Researchers say these new studies should...