Hydrocephalus is a condition which quite literally means water on the brain. The water in question is in fact cerebrospinal fluid (CSF), a clear, colourless fluid which is made in constant quantity of about 500 ml each day. It bathes the surface of the brain and spinal cord, as well as there being fluid spaces within the brain which are occupied by CSF (the ventricles). Hydrocephalus is a condition in which there is an abnormal build-up of this fluid.
How does hydrocephalus develop?
CSF is produced within the ventricles and then flows through a specific route within the brain to reach the brain surface from where it is absorbed away back into the bloodstream. Hydrocephalus can result either when there is a blockage to the flow of the CSF through the various channels in the brain, or where there is a mismatch between the production and absorption. The former is referred to as obstructive or non-communicating hydrocephalus and the latter as communicating hydrocephalus.
Obstructive hydrocephalus is usually a mechanical issue and can be caused due to distortion of the brain anatomy, for example with some tumours. Communicating hydrocephalus on the other hand is usually due to impaired absorption of CSF and most commonly this happens after a bleed within the brain or an infection within the brain.
What symptoms does it cause?
The symptoms of hydrocephalus are those of raised pressure inside the head. These include headache, drowsiness, nausea and vomiting, unsteadiness, blurring of vision and cognitive impairment. These symptoms can occur in a variety of other far commoner conditions, and it is very rare that they will be indicative of a new diagnosis of underlying hydrocephalus.
What is the treatment for hydrocephalus?
The treatment of hydrocephalus will largely be determined by the type of hydrocephalus. It will also depend on whether the cause of the hydrocephalus is thought to be temporary or permanent. If the hydrocephalus is caused by something that is likely to be reversible, then a short-term solution can be to drain some CSF from the lower spine (a lumbar puncture). However, the majority of patients with hydrocephalus require a more permanent solution, and this will entail surgery.
For obstructive or non-communicating hydrocephalus, it can be possible to relieve the hydrocephalus by relieving the point of obstruction or bypassing the CSF around it. The cause of a blockage in the flow of CSF might be caused by an abnormality such as a tumour. Surgery to remove such a tumour can then potentially relieve the hydrocephalus. However, there can be other congenital obstructions to CSF flow, the most common of which is a condition called aqueduct stenosis. This is best treated by bypassing CSF flow and the most common procedure for this is an endoscopic 3rd ventriculostomy. This involves puncturing a hole through the floor of the 3rd ventricle (one of the fluid spaces containing CSF) so CSF can thereby bypass to the surface of the brain from where it can be absorbed away. An endoscopic 3rd ventriculostomy is a relatively straightforward procedure done through a burr hole in your skull and using an endoscope to guide the procedure. It will usually just involve one or two days in hospital if successful. It often provides a long-term cure for hydrocephalus, although on occasion they can close over and the procedure needs to be repeated.
If the cause of hydrocephalus is impaired absorption of CSF, then no procedure to bypass CSF flow is going to help this. In this situation, a shunt is the surgical treatment of choice. This involves taking CSF from one of the ventricles in the brain and diverting it elsewhere, usually to the abdominal cavity, from where it can be absorbed away.
A ventricular peritoneal (VP) shunt is a relatively straightforward operation which allows this diversion of CSF. A small piece of tubing is placed into the ventricle in the brain and then connected to a valve which characteristically sits underneath the skin behind the ear. This valve will regulate the amount of CSF that passes through the shunt as well as ensuring that the flow is only one way. It also provides a point of access whereby CSF can be drawn off the shunt if required. The valve is then connected via a further piece of tubing running underneath the skin down through the neck, over the chest wall and to the abdomen. A VP shunt usually only requires a 1 to 2 day stay in hospital.
Whilst a VP shunt is an excellent way of treating hydrocephalus, it can be associated with its own set of problems. These include shunt blockage, infection, and/or over-drainage. If a shunt is likely to be required, your surgeon would clearly outline the nature of these risks in far greater detail.
This scan shows a VP shunt (the white tube) inserted into the ventricles
of the brain to relieve hydrocephalus