Well I learned something today. In my 37 years of hunting I have never heard of nor seen these.
If you saw the head off and let it be you may never see them. I have done many European mounts, cleaning the skin/flesh off the head removing lower jaw etc. you will find them on almost every deer, at least I do.
If you dove hunt pay attention to their guts when you breast one out, they will have worms in them too.