Came across this study of 58 people with MS and 13 healthy controls that found an association between IJV blood flow (wash out rate) and disability levels.
Internal Jugular Vein Blood Flow in Multiple Sclerosis Patients and Matched Controls (full article available) From the abstract:
A significant correlation was found between Internal Jugular Vein wash-out and level of disability (R = −0.402, p<0.05).
From the article itself:
In conclusion, these results suggest that ...