I think migraines are thought to cause lesions.

http://www.neurologyreviews.com/mar0...migraines.html

I don't know if there's any way to determine the CAUSE of a lesion, be it multiple sclerosis, migraines, etc. Sometimes they can be differentiated by size/location or appearance or pattern. MS is also known to produce headaches too, so it becomes very difficult to say what causes what. I really don't think a PA is qualified to say that an occipital lesion is due to migraines and has no relationship to your vision troubles. The occipital lobes play a part in vision.

See here:

http://www.neuroskills.com/tbi/boccipit.shtml

Multiple sclerosis requires more than one neurologic event separated in space and time from another. So one lesion normally won't qualify you for a diagnosis unless there is a distinct other neurological event at some other point. Of course it could BE MS, but it usually isn't diagnosed until there is more than one event or evidence of more than one neurological event (i.e., more than 1 lesion).