I don't know if some insurances are rationing visits to specialists. It's a crying shame, if so. You need a neurologist or at least someone who can read MRI's. A few pcp's can do this. But not all.
I guess no one has an answer for my periventricular question. It seems anyone reading this has not been told lesions must be periventricular for diagnosis. That could just be a ludicrous myth which an early neurologist told me, early in my own dx. That's one problem you will face if you DO get a neurologist, that they have disagreements and they are not all equal in skill.