Since none of the answers from those "in the know" seemed quite right to me, I searched out a pediatric neurologist and had him examine Eliza this week. He was lovely, kind and supportive.
And very certain that answers (a) through (d) were, shall we say, bullshit (my word, not his).
Just to put this in perspective, here is a photo of Eliza speaking:
Figment of my imagination? I think not.
It seems this facial asymmetry could be caused by one a few problems, none of which is something you want in your household. So the new short list of choices is (in my layman's terms):
(a) "Extreme Preemie Brain." For those of you who have been following along for a while, I posted this diagram a while back:
:

My personal belief (and that of quite a few people in the post-NICU business) is that you just can't take one of these partially developed 26 week brains that is meant to be happily floating in a dark, warm pool of amniotic fluid, drag it out into the glaring light of day in a NICU with all hell breaking loose, with limited regard for pain and sensory management and hope that this brain will develop normally. So, this problem of Eliza's could be just one more gift of extreme prematurity with no particular explanation or solution.
(b) Something like Periventricular Leukomalacia (PVL) that was not seen in Eliza's NICU head ultra sounds. It is not unheard of for this to only be diagnosed later in a brain MRI. For your reading pleasure, you can go here: http://emedicine.medscape.com/article/975728-overview
(c) A brain cyst/lesion/tumor/etc.
(d) Who the hell knows
Where does this leave us? Well first Eliza will have a brain MRI. Because Eliza will need full sedation for this she cannot be sick in the preceding two weeks. So for those of you who plan on visiting, you will not be welcome here if you are sick, have been sick, been near sick people or refuse to wash your hands and remove your shoes when you come in our apartment.
Hopefully the MRI will give us some guidance as to what the problem is. From there, well who knows. Eliza and I will cross that bridge when we come to it, just like we have many times before.
Oh, and the next person who tells me to lighten up about this "prematurity thing" may not be all too happy with my reaction.