Interesting... have you researched it much? Google it and you get lots of things from potential trauma, to infection, to tortion, to who knows what else.
Which is why I began thinking it might be a parasite, or at least that I should explore the possibility as sometimes things that have several explanations are something else entirely.
Anyway, please keep me and the board posted with your thoughts and any research you happen to come up with. I will do the same.