Yeah, migraines can mimic pretty much any other neurological event, including all sorts of epilepsy symptoms.

I knew they could mimic one-sided symptoms, because one of my relatives has that kind of migraine (and thought she was having a stroke the first time one showed up), but I didn't know about things like speech centers.

[edit] ETA: commenting in the spirit of "yes, this is a wild and weird and potentially scary thing", not meaning to sound like this is a thing you should already know or anything.

Understood. I feel I should have known it (because of the family history: I like to think I would have made the connection if half spatch's vision had blinked out), but I also feel it would still have been the right decision to go to an ER, because it isn't like we have metoclopramide lying around the house. It would just have been nice to be able to say to the triage nurse straight off, "This might be a migraine," rather than, "He can pass a coordination test and his pupils are the same size, he just can't speak." I thought of unusual anxiety levels, but migraine didn't cross my mind.

(I get migraines, but they are limited to pain, light sensitivity, noise sensitivity, and nausea—and they have a known and specific trigger—so handling them has always been a matter of pain management and waiting rather than actually medicating the migraine away.)