I've had pain & numbness in my legs & feet for a few years now. My primary Dr finally sent me to a Neuro. She in turn did an MRI, which showed 8-9 lesions. Then she did a spinal tap which she said came back negative. Still she is very unsure what it is. She wants to treat me for MS starting with Avonex for 8 weeks then do another MRI, but still no definited diagnosis.
Your story places your neuro at the "pretty aggressive" end of the doctor scale, but not off
the scale. Many docs are willing to treat CIS (clinically isolated syndrome) as if it were a MS dx, on the theory that the DMDs probably
won't hurt anything (much), while MS will for sure degrade your CNS. Even so, she should have also told you that there is no way to know if Avonex or any other DMD will actually improve your sx.
As for the dx itself, she can't 'officially' call it MS until there are multiple
(M) damage sites (scleroses, or S) that are also separated in time, per the currently accepted criteria for MS. So far there's just one snapshot, apparently with no evidence that some lesions are more recent than others. The point of going back for MRIs is to look for new lesions. Until new lesions appear, a good neuro will keep looking for evidence of MS or anything else...