Quote (Azrad @ Apr 8 2013 05:33pm)
http://en.wikipedia.org/wiki/Hydrocephalushere are some (disturbing) pictures of very young children with it, which seems rather consistent with the mummy.
http://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Hydrocephalus-baby.jpg/200px-Hydrocephalus-baby.jpg
http://s22.postimg.org/rfqb5cg35/head25f_3_web.jpg
http://s24.postimg.org/86rcmanph/Chun_Xin.jpg
And assuming this is the case for the mummy, this isn't even the first time there have been claims of babies with hydrocephalus being aliens. Similar claims surfaced in Brazil in 2004 until testing showed the "alien" in question was in fact a sadly deformed human child

Progeria is another disorder that can cause abnormal bone growth, most specifically noticed in the cranium.
http://en.wikipedia.org/wiki/ProgeriaMost likely, I would say you're more spot on to what caused the abnormal growth as shown in the OP. The enlargement is more consistent with your assumption.