This is just a guess, but as such I wouldn't be surprised if that elbow retriggered TBI symptoms. My Chronic Fatigue Syndrome started with my head injury. In fact this is a fairly common way to get CFS. I believe that Chronic Fatigue is essentially an out-of-control immune reaction. I have no idea the mechanism, i.e. how a brain injury would trigger an immune system reaction, but the correlation is there as far as I'm concerned (I'm working on some theories, though.)