Your initial sign would certainly appear to be similar to a mini-stroke. Your LP result, although clear, may always be clear. I have had 2 LP's (1982 and 2002). Both were clear and yet I have MS. You might very well fit the same category. Have you had a VEP? It is good you had your MRI.
Many doctors are not quick to diagnose. Your testing seems to be on track. If you do have MS, please let us know. In the meanwhile, I will keep you in my prayers.