“…In a case of pathological venous outflow from the brain, some patients present with diminished inflow to the IJV resulting from decreased cerebral venous flow, primarily caused by neurologic disease (eg, reduced cerebral metabolism, brain atrophy), from atypical anatomy of the cerebral sinuses (such as hypoplasia of one or both of transversal and/or sigmoid sinuses), 110,111 or a combination of these. In some individuals, one or both IJVs are found to be externally compressed, usually by aberrant adjacent muscles (Figure 6), 34,112 arteries, 113 or bony structures. 30,32,37,40,[46][47][48] Such compression may also result Chronic cerebrospinal venous insufficiency from reduced rigidity of the venous wall that, for reasons not presently well understood, perhaps altered composition of collagen fibers, is seen in some patients with multiple sclerosis.…”