I got a concussion about 3.5 weeks ago. Had a gnarly fall off a jump and felt weird the whole rest of the night and the next day at work. I walked down the hill after I hit, because i was dazed, but rode the whole rest of the night. Dr. said to stay away from any activity with a risk of hitting my head for 3 weeks. Staying off my board that long sucked, but better than permanent brain damage.
I'm looking at helmets now, but probably won't until I start doing a decent amount of park. I am still a beginner/intermediate rider and enjoy just freeriding, and don't have many hard falls just riding around.