Hydrocephalus is a congenital or acquired disorder characterized by the abnormal accumulation of cerebrospinal fluid within the cavities of the brain, called ventricles. The accumulation of cerebrospinal fluid, the clear fluid surrounding the brain and spinal cord, causes an abnormal widening of the ventricles. The widening creates potentially harmful pressure on the tissues of the brain that can result in brain damage or death. The most obvious sign of hydrocephalus is the rapid increase in head circumference or an unusual large head size due to the accumulation of cerebrospinal fluid in the brain. In infants, hydrocephalus can be caused by congenital factors such as malformations of the brain, or acquired factors such as tumors, cysts, meningitis, or bleeding. Treatment after the infant is born can lead to normal cognitive and physical development with few limitations.