Hydrocephalus comes in two types: obstructive hydrocephalus and communicating hydrocephalus. Obstructive hydrocephalus is characterized by the inability of cerebrospinal fluid (CSF) to flow from the brain to the spinal cord, preventing normal circulation. In this situation, the pressure inside the skull can gradually increase due to the buildup of fluid, potentially leading to the progressive bulging of a child's fontanel. On the other hand, communicating hydrocephalus involves the CSF being able to circulate between the brain cavities and the spinal cord, merely resulting in an enlargement of the ventricles without the bulging of the fontanel.