Today's news was relatively good—with an emphasis on the relative. They've confirmed that my face droopiness wasn't caused by a stroke. There were no ischemic problems on the MRI.
So what is it? A neurologist just came by and was generally pleased with everything, including the fact that my droopiness extended all the way up my face. He says the cause is almost certainly a virus that inflamed a facial nerve, and it will probably take about three weeks to resolve. Yuck. In the meantime, I have trouble pronouncing b's and p's, and lots of trouble drinking water. The treatment for this, sadly, is plenty of dexamethasone, and you can imagine what that's doing to my sleep.
My counts are slowly increasing back to normal, and I can walk fine with no balance problems. I also have no fevers and no signs of neurotoxicity. So that's all good. I'm still very tired all the time, though.
Bottom line: this is Day 20 and it's all very unexpected, but getting better.
UPDATE: The latest diagnosis is Bell's palsy. No change in symptoms or treatment, though.