Hi, Thanks for writing in. After a concussion or mild brain injury some people lose consciousness or are “knocked out” for a short time, but not always -- you can have a brain injury without losing consciousness. Some people are simply dazed or confused. Sometimes whiplash can cause a concussion. Because the brain is very complex, every brain injury is different. Some symptoms may appear right away, while others may not show up for days or weeks after the concussion. Sometimes the injury makes it hard for people to recognize or to admit that they are having problems. The signs of mild brain injury and concussion can be subtle. Early on, problems may be missed by patients, family members, and doctors. People may look fine even thought they’re acting or feeling differently. Because all brain injuries are different, so is recovery. Most people with mild injuries recover fully, but it can take time. Some symptoms can last for days, weeks, or longer. Hope this helps