Hello Sham,

It is possible to have MS but no evidence on MRI. For some, it can take time for MRI evidence and if you have MS sooner or later there will be MRI evidence of the disease.

However, the more years that go by and MRIs continue to be negative the less likely MS becomes. There are other tests, if positive, that can be taken into consideration for a diagnosis of MS.

There is a criteria for diagnosing MS, the McDonald Criteria.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3084507/

I was given a definite diagnosis of MS with a clear MRI.

However, I had what I refer to as the "perfect storm." I was in the middle of a severe exacerbation (relapse, attack, flare-up), positive Lumbar Puncture (LP) and a Neurological exam that I completely failed.

I don't know when lesions first appeared because I never had another MRI until 20 years after diagnosis.

Best wishes!