Multiple sclerosis is a long term progressive autoimmune disease that affects the brain and the spinal cord. For unknown reasons, the immune system attacks some structures of its own body during MS. In particular, the myelin coverings of the nerves and nerve tracts are destroyed by the immune system. Myelin destruction appear as plaques. Plaques can be found anywhere in the brain. The symptoms will depend upon the plaques’ location. during MS, these "plaques" can heal but not completely. That’s why some symptoms can vanish in time but not completely. When a new plaque is formed then new symptoms show up. There is no specific marker for diagnosing MS. Diagnosis of MS can be established according to the results of several diagnostic procedures:
1. “Attacks” consisting of more new symptoms with incomplete remission;
2. Physical examination (neurological status);
3. CT/MRI image of the brain (positive in 95% of cases;)
4. Laboratory analyses of the cerebro-spinal liquor (lumbar punition) (positive in 70% of cases);
5. Evoked potentials can be visual (VEP), audio (AEP) and sensitive (SEP). VEP are positive in 20-30% of all cases, SEP in 60% and AEP in 50-70% of all cases with MS.

According to this I can tell you only that IT IS POSSIBLE to have MS and not to show up on VEP or lumbar punition. Please see a specialist if you suspect that you are experiencing symptoms of the illness.