As immisceo said, monocytes are not really on the MS diagnostic radar. They are a kind of white blood cell and an elevated count may mean nothing more that the presence of some type of nonspecific inflammation or infection.
The Holy Grail in CSF findings is unique oligoclonal bands. This means there are o-bands present in your CSF that are not present in your blood. The second item of note in the CSF results is the IgG number. Elevated IgG numbers indicated inflammation in the central nervous system.
It looks like there is a good bit of research into establishing some sort of connection (finding biomarkers is a bit of an MS research holy grail). I just popped "monocytes multiple sclerosis" into google and got a few National Institutes of Health results.
I'm not sure that anything causal or directly correlated has been sufficiently established yet (but I really only gave it a cursory glance). I would say that I never heard them mentioned in my diagnostic process.
In this special Missouri Medicine report, doctors examine advances in diagnosis and treatment of this devastating and costly neurodegenerative disease.