Impacts on abdominal veins can abruptly push lumbosacral subarachnoid fluid headwards. In momentarily engorging epidural veins.

At a myelogram I did in the early 1970ies, the patient's coughing also made the contrast medium instantaneously disappear.

A later thesis characterized such occurrences as

"piston strokes."

Can't CSF piston strokes that go in the opposite direction not also emerge from blood volumes driven up along internal jugular veins? Especially in boxing or blast impacts loading chest or neck?