It could be upper cervical inflammation. That does not mean a concussion. It is easy to aggravate a neck injury and cause inflammation. If you are dizzy when you stand up, take you time standing up. I have to get up in 2 steps. I move to the front of the chair, pause for a brief moment, then I stand up. I only move in one dimension at a time. Been that way since orthopedic surgery in 1987.