I know this thread is several years old, but since it's still active I am posting for future readers.
The post-concussion symptoms can last much longer after the doctors have "cleared" the concussion. My son was cleared for about a month and then went to a loud arcade and played simulation-like video games and came home with symptoms again. He had to rest the remainder of the day with a headache and nausea.
If someone is going to Disney and dropping thousands of dollars, it would really be a shame to have to spend a day (or the week!) in bed b/c the first ride you went on brought back concussion symptoms.
Anyone else experience concussion-related reoccurrence issues on rides other than Expedition Everest? I would assume orange Mission Space would be problematic. What about Flight of Passage?