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/head.
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 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 and it is then 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. 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
- 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 and Spina Bifida
Spina bifida condition which affects about one in every 1000 children born per year in Ireland. Ireland has one of the highest incidences of spina bifida births in the world. Spina bifida is the most common neural tube defect (NTD) which causes incomplete development of the spinal cord. Translated, it literally means 'split spine'.
Whilst hydrocephalus is a complication of spina bifida occurring in approximately 65% of cases, it is by no means exclusive to spina bifida. For more information, visit our Spina Bifida page.
Hydrocephalus and Epilepsy
About 1:3 children with hydrocephalus will develop epilepsy which will be treated by a neurologist.
Although epilepsy is commonly associated with shunt-treated hydrocephalus, its relation to the shunting procedure and the criteria identifying postoperative epilepsy remain controversial. The complications of CSF shunt surgery seem to play a relatively minor role in the development of epilepsy.
For many children no cause is identified. Where causes are known they range from genetic and inherited conditions, head injury, brain infections (meningitis/encephalitis), developmental brain disorders, birth injuries, cerebral palsy, hydrocephalus and, more rarely, tumours.