What is Hydrocephalus?


Hydrocephalus comes from two Greek words

The term Hydrocephalus comes from the two Greek words: 'hydro' which means water, and 'cephalus' which means head. In years past, it was commonly called 'water on the brain'. Put simply it is a condition where there is too much cerebrospinal fluid in the cranium.

Cerebrospinal fluid (CSF) is found within the brain and the spinal cord. It is a clear, watery substance that flows through a channel into the space (subarachnoid space) around the brain and spinal cord, where it also functions as a cushion. The CSF is absorbed back into the bloodstream via mushroom-like structures over the brain called and replenished. A small amount of CSF is produced by the spinal cord. The CSF contains nutrients and proteins necessary for the nourishment and function of the brain and carries waste products away from tissues in and around the brain.

The fluid is produced within hollow channels in the brain called ventricles, primarily within the lateral ventricle. In each ventricle is a specialised structure (which looks like small flower-like tufts) called the choroid plexus, which is responsible for the majority of CSF production. This CSF is produced at a constant rate.

The brain maintains a balance between the amount of cerebrospinal fluid that is absorbed and the amount that is produced.

Hydrocephalus occurs when there is an imbalance between the amount of CSF that is produced and the rate at which it is absorbed. This can be caused by a blockage in the pathways through which the fluid travels or from an overproduction of fluid or a difficulty in absorbing the fluid that is produced. Because the brain is enclosed within the skull, the extra fluid has no escape which causes it to build up. This then causes the ventricles to enlarge and the pressure inside the head to increase, resulting in an enlarged head and increased pressure symptoms.



Hydrocephalus can be identified in one of two ways – Congenital and Acquired.


Congenital Hydrocephalus results from a complex interaction of genetic and environmental factors and is present at birth. It is important to remember that the term genetic does not imply that it is hereditary. Often the exact cause of congenital Hydrocephalus cannot be determined. Though it might not be recognised and diagnosed immediately, congenital Hydrocephalus is often diagnosed before birth through routine ultrasound. Hydrocephalus diagnosed in adulthood may have existed since birth and can still be considered congenital and may be referred to as compensated Hydrocephalus.


Acquired Hydrocephalus develops after birth as a result of neurological conditions. This type of Hydrocephalus can affect individuals of all ages and may be caused by head trauma, brain tumour, cyst, intraventricular haemorrhage or infection of the central nervous system.

Within both of these areas, congenial and acquired, Hydrocephalus can be described as communicating or non-communicating. Communicating Hydrocephalus occurs when the flow of CSF is blocked after it exits the ventricles. This form is called communicating because the CSF can still flow between the ventricles, which remain open. Non-communicating Hydrocephalus – also called "obstructive" Hydrocephalus occurs when the flow of CSF is blocked along one or more of the narrow passages connecting the ventricles.

There are two other forms of Hydrocephalus which do not fit exactly into the categories mentioned above and primarily affect adults: Benign External Hydrocephalus and Normal Pressure Hydrocephalus.

Congenital Hydrocephalus

This means that Hydrocephalus is present at birth. It is important to remember that this term does not imply that it is hereditary. Often the exact cause of Congenital Hydrocephalus cannot be determined.


For further information go to, you will find information in relation to Spina Bifida, Hydrocephalus and services offered by Spina Bifida Hydrocephalus Ireland.

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