There are two main types of hydrocephalus

• Congenital hydrocephalus—occurs before, during, or soon after birth, or later in life because of a medical condition that existed at birth



• Acquired hydrocephalus—occurs later in life because something is preventing the cerebrospinal fluid (CSF) in the brain from draining properly



• Communicating hydrocephalus—occurs when something prevents the CSF from circulating properly. It is called “communicating hydrocephalus” because the parts of the brain that circulate the CSF are not communicating or “talking to each other” properly.



• Non-communicating (obstructive) hydrocephalus—occurs when something blocks the flow of CSF so it cannot circulate properly.

Hydrocephalus is also categorized by the effect it has inside the skull:

• Normal-pressure hydrocephalus (NPH) —causes swelling of the brain like other types of hydrocephalus, but without the resulting increase in pressure inside the skull. This type of hydrocephalus usually occurs in older people, and mostly in those who are 60 years old and older. NPH is usually caused by an obstruction in the flow of CSF. There are two types of NPH:


• Idiopathic NPH—means that the cause is unknown. Most cases of NPH are idiopathic.


• NPH of known cause—such as head injury, tumor, cyst, bleeding in the brain, and infections such as meningitis .