Hydrocephalic skull. Historical illustration of an enlarged hydrocephalic skull. The condition hydrocephalus, or inswater on the brainins, is the excessive production of, or a block in the circulation of cerebrospinal fluid in the brain cavities. The condition can be caused by injury or it can be congenital (present from birth). In children, where the skull bone plates have not yet fused, an enlarged skull can result, as seen. The condition can be fatal if left untreated. Illustration from a book published in 1820.