on page 1352 Dr. Zamboni notes this about PPMS patients in his study:
"Type D pattern (18%) is characterized by the multilevel
involvement of the AZY and lumbar systems. Association
with the IJVs was observed in approximately 50%
and caused an additional obstruction in these patients.
It was observed in two of 35 RR patients, in one of 20
SP patients, and in nine of 10 PP patients."
So there is a correlation between type of MS and location of stenosis.