My 17 year old son noticed several months ago a rather large concave indention in the back of his skull on the one side. It does not hurt but it is pretty sunken in, maybe 1/4 to 1/2 inch. Just recently he noticed he is getting one on the other side of the back of skull. He does not really suffer from headaches. But he does complain occasionally of dizziness. Saw a doctor today and a CT scan w/contrast has been scheduled. The doctor had no idea what it was. I am very concerned and am searching for some answers.