It is not uncommon for accident victims to sustain a concussion. This can occur when the head strikes a window, the steering wheel, or the back of a seat during impact. With time, concussion symptoms may and can resolve.
However, second impact syndrome occurs when the brain has not healed from the initial concussion. If the brain has not healed, a second impact can cause swelling of the brain or hemorrhaging. This in turn can lead to death. Fortunately, second impact syndrome is infrequent. However, it is critical to avoid activities that could cause it to occur.