I found a great article that distinguishes the difference between PTSD and TBI. Apparently studies show that victims of TBI usually do not develop PTSD because TBI is more often followed by loss of consciousness and amnesia. As described, the loss of memory can serve as a protective agent against the formation of PTSD. Those who remember and were not necessarily out of consciousness for a long duration at the time of the event are more likely to develop PTSD. They are in fact cognitively healthy and physically healthy. But emotionally they are going through a stressful situation. The symptoms of PTSD and TBI are almost identical in nature. But the anxiety and fear are a lot more severe in those with PTSD. Depersonalization is also highly particular in PTSD patients. The way in which the traumatic stress episode is re-experienced should thus differ depending on the amount or type of memory loss. So if you had a loss of consciousness for a long period of time the chances of PTSD is unlikely. Whereas if you remember the event prior and during and were out for a split second or maybe not at all the chances of developing PTSD are much greater. Pathological memory formation during an alarm response may set the precondition for PTSD to occur. So if you remember the event and there was no significant loss of memory or consciousness there is a good chance you are suffering from PTSD or its acute variant. Remember both have similar symptoms but the depersonalization and severity of stress / anxiety is more common in PTSD.