“Sounds like they trephined his skull to keep swelling from damaging his brain. Fear of subdural swelling.”
probably more than trephining; they do something called “hinge surgery”, which i understand is where a large piece of skull is cut loose around three sides, but the fourth side only partially cut to allow a continuing blood supply ... they do that only when the stroke is severe enough to produce brain swelling, so despite all the happy talk about a “full recovery”, this was a severe stroke ... this guy isn’t going to be up and around any time soon, if ever ...
posterior strokes are the most likely to require decompressive craniotomy . The cerebellum is densly encased by bone and swelling would tend to herniate down the brain stem. It is not that unusual and does not necessarily mean devastating injury