On these concussions- I sort of liken them to a "pinball machine" going on tilt. When you shake and jar the machine to much, you upset it's natural equilibrium, and the machine shuts down-- in order to protect itself.
When a person is hit hard enough and the head is "jolted" the brain collides with the inside of the skull, and maybe creates a small bruise on the brain. It's the body's natural response to protect itself by creating these symptoms, causing a need for rest, until the brain fully heals and there are no more symptoms. It's a matter of time, for this to heal.
I recall players like Eric Lindros, Laine and Crosby taking big hits and having concussions, but eventually they came back to full operational capacity, so I don't think Trouba is injury prone like some people suggest. He just took a big hit, and it's really the first time he's had this sort of injury. I think he will be just fine, with a little time.
My guess is that he'll be back in about 10 days or so ( maybe sooner) and be playing very well, and things will get back to normal.