I have recently discovered two dints in my skull ..they have only just appeared, never been there before. There is a lump which is solid between them and the whole thing resembles the shape and size of a slug, approx 5cms long and 1cm wide. It runs from my hair line at my forehead back to the middle of my head. These were noticed about 8wks ago and I have ignored them, but one a new indentation has appeared in my forehead, right underneath where the other two are...what could it be?