Hydrocephalus

Hydrocephalus is the abnormal buildup of fluid within your brain. Hydrocephalus comes from the Greek words “hydro,” which means water, and “cephalus,” which means head. Hydrocephalus was once known as “water on the brain.” The “water” is actually cerebrospinal fluid (CSF) — a clear, colorless fluid surrounding your brain and spinal cord.

Normally, CSF flows through areas in your brain called ventricles. CSF serves as a nutrient delivery and waste removal system for your brain. CSF bathes your brain and spinal cord, protecting and cushioning them from injury. CSF is then reabsorbed into your bloodstream.

Your body usually produces the CSF it needs each day and then reabsorbs the same amount. However, when the normal flow or absorption of CSF is blocked, it can result in a buildup of CSF. As the CSF builds up, it causes the ventricles to enlarge. This causes pressure inside of your head to increase. The pressure from too much CSF can keep your brain from functioning properly.

Who can get hydrocephalus?

One to 2 of every 1,000 babies in the United States are born with hydrocephalus. But hydrocephalus also affects older children and adults of all ages.

What are the different types of hydrocephalus?

The four main types of hydrocephalus are communicating hydrocephalus, non-communicating hydrocephalus, normal pressure hydrocephalus and hydrocephalus ex-vacuo.

• Communicating hydrocephalus occurs when the flow of CSF is blocked after it leaves your ventricles. This type of hydrocephalus may result from a thickening of membranes at the base of your brain called arachnoid. This blockage prevents the free flow of CSF. This type of hydrocephalus is called communicating because the CSF can still flow between your ventricles, which remain open.
• Non-communicating hydrocephalus is also known as obstructive hydrocephalus. Non-communicating hydrocephalus occurs when the flow of CSF is blocked along one or more of the narrow passages connecting your ventricles.
• Normal pressure hydrocephalus (NPH) happens when CSF buildup causes your ventricles to enlarge, but there’s little to no increase in pressure. The difference between NPH and other types of hydrocephalus is that even though there’s a larger than normal amount of CSF, the pressure inside of your ventricles remains the same. The buildup of CSF in your ventricles happens slowly and symptoms occur over time. NPH happens most often among the elderly.
• Hydrocephalus ex-vacuo results from brain damage caused by head injury or stroke. In these cases, brain tissue around your ventricles shrinks. CSF builds up in your ventricles to fill in the extra space. Your ventricles are enlarged, but pressure in your head usually remains normal.

Another word you may see or hear when learning about hydrocephalus is ventriculomegaly. Ventriculomegaly is the term used when the ventricles of a fetus’s brain are enlarged. Hydrocephalus may be the cause of the ventriculomegaly, but there are other reasons this enlargement might happen.