[trux]

Hm, interesting, I never heard about cavities in the back of the skull (except the big one where normally brain resides). I tried looking it up now on Internet, but all documents speaking about sinus cavities only show paranasal sinus cavities that are in the facial part. I did not manage to find any reference to any cavity in the back of the head. It does not mean I do not believe you, but would like to know more about it. Could you post some reference to them, or perhaps their exact location?