Prevalence of extracranial venous narrowing on catheter venography in people with multiple sclerosis, their siblings, and unrelated healthy controls: a blinded, case-control study - Traboulsee, A L; Knox, K B; Machan, L; Zhao, Y; Yee, I; Rauscher, A; Klass, D; Szkup, P; Otani, R; Kopriva, D; Lala, S; Li, D K; Sadovnick, D (Lancet, 2014)