I Have These Episodes That I Stand Up And It

I have these episodes that I stand up and it seems I black out with no advance warning I fall face first into anything that happened to be in front of me. At times I end up in a bloddy mess on the floor. I don't even remember falling or trying to protect myself from the fall. On November 3 1013 I was hit on the top of the head with a roll of carper and crushed 3 , c 5-6-7 vertebre. the fusion went very well - PT is working but I still fall not sure what it is - I have had brain scan and other mri's and ct's with no clear diagnosis. It has been almost 19 months. can you help/ PLEASE