Yes, larae, I am one who has no lesions (that they've found yet) and no Obands via the LP... however, by all accounts thru a neuro exam and nerve conduction test and Optic Neuritis, my neuro has dx'd me with MS as of March this year. He calls it "benign".
The other thing he points out is that Standard MRI machines are 1.5 Tesla magnets, while some more specialized others are 3.0 Tesla magnets... and open MRI's are .5... this all makes a difference because some lesions won't show up every time on the standards.
Your neuro will know. It's a long arduous ordeal of monitoring and testing, reporting symptoms, keeping journals etc. All this leads the neuro to a conclusion when he gets enough info to confirm it to him. As Gretchen pointed out, it is "multiple" so if you have everything in just one area like all numbness or legs only etc... then that's only one area of issue, whereas, balance, numbness, and Optic Neuritis then makes it conclusively multiple. Be patient and keep a journal of your symptoms it'll be helpful to the drs.