Kingsley is fine, just fine.
We saw his neurosurgeon today. She said his syrinx is still there, still significant, but stable. She asked a whole bunch of questions about what we've been seeing, what Kingsley has been doing, what the concerns are, what changes he's had. She believes they are because he is doing so much more, using so many more muscles in different ways and so there are some side effects - his hamstring is tight because he's realized he can bend that knee to move around and so bends it (he doesn't have the quad muscles to stretch it straight again). The increased twitching is enervation and conscious movement where before it was passive. He's just doing well.
One small shadow: his Chiari area is a bit tight. She asked about his eating and if he chokes and whatnot. He isn't showing any symptoms that concern her, so no surgery now. She is not keen to jump in and open it up more without a really good reason, as doing so could cause more problems so there's no point in putting that risk out there without a very good reason. The same with putting a shunt in his spine to drain the syrinx - there are no guarantees that it would help the situation and no guarantees that it wouldn't make things worse. So, while everything is stable, no surgery. If he has significant changes, we'll have to look into those things.
More good news! His brain is perfectly wonderful. His shunt is working perfectly. There is nothing there that would be causing language problems, as far as she could see, so the delay is just a delay that he will work through, as far as anyone can tell.
This is all pretty much beyond what I could've hoped for. I was imagining terrible things and not a single one of them came true. It's like Christmas morning, his birth day and winning the lottery all in one.
This afternoon, my sister came home to celebrate with us. Really, they came home for Christmas, but this was a pretty good second reason. ;) Christmas can officially begin again. All is well.