I chose my imagination because it fit the best, but in reality it was the imagination of a really grumpy pediatric GI specialist my son saw (my nickname for her was GI Jerkface, we ended up finding a doc who was not only friendlier but a bit more knowledgeable about my son's condition)
my son had growth issues during his first year and his head just looked huge. It measured large as well, way out of proportion with his teeeeeny body but normal for a kid his age. His head was around 50% on the charts, his body around 3%, he was a VERY sick boy.
Just as he started gaining weight the GI doc told me she thought there was "something growing" in my son's head and had me take him to our ped that day and the ped had to send him for all kinds of tests.
The ped measured his head and said it was completely normal and he marked the visit as a "worried mom" visit, but I was never worried abotu his head, I was more worried about the fact that he was 9 months old and 11 lbs (7lbs 9 oz at birth).
That and my kids all have large heads, they just do!
Meg