Hydrocephalus is sometimes known as ‘water on the brain’. A watery fluid known as Cerebro-spinal Fluid (CSF) flows through narrow passageways from one ventricle (chamber) to the next, then over the inside of the brain and down the spinal cord. CSF is continuously absorbed into the blood stream and the amount of pressure within the brain is kept within a narrow range. However, if the flow of fluid is obstructed at any point, it accumulates in the ventricles causing them to enlarge and compress surrounding brain tissue. In babies, but not in older children and adults, one sign of it is an enlarged head.
What causes hydrocephalus?
Congenital Hydrocephalus is caused by something that affects the development of the foetus in the womb, and is present at birth. This does not mean that it is hereditary. There can be various causal factors, including an infection in pregnancy, bleeding in the developing brain, or a physical malformation of part of the brain.
Prematurity. Babies born prematurely are at risk. The area which lies just beneath the lining of the ventricles in the brain is particularly important. This area has a plentiful blood supply and its blood vessels are fragile. They can burst if the baby suffers too large a swing in blood pressure or becomes severely ill from other causes.
Spina Bifida. Most, though not all babies born with spina bifida also have hydrocephalus. In spina bifida there is an abnormal opening in the spine, affecting the spinal cord, and this can prevent proper drainage of the CSF, increasing the pressure.
Other forms. Brain haemorrhage, including "stroke", can result in post-haemorrhagic hydrocephalus.
Meningitis. This is an infection of the membrane covering the brain. Inflammation and debris from this infection can block the drainage pathways, resulting in hydrocephalus.
Dandy Walker Cysts. A group of disorders in which fluid-filled cysts form in the CSF system. Hydrocephalus can arise from pressure on the surrounding tissues by the enlarging cyst.
Tumours. Tumours cause compression and swelling of surrounding tissues, resulting in poor drainage of CSF. In the treatment of brain tumours, it is often necessary to include measures to control hydrocephalus, which might only be temporary.
Genetic. In very rare circumstances, hydrocephalus is due to hereditary factors, which might affect future generations.
The effects
A physical problem may be seen in the eyes ("papilloedema", swelling of the optic disc), but is not present in all cases. It is caused by pressure on the blood supply to the back of the eye. If CSF pressure remains high for too long, damage to the optic nerves can become permanent, resulting in blindness. (This is now uncommon.) Another effect, particularly in babies, is the ‘sunset’ eye sign, where the eyes are fixed in a downward position. This is due to CSF pressure affecting key nerves running from the brain that control eye movement.
Many of our vital functions, such as heartbeat and breathing, are controlled from the brain stem. This is a structure joining the spinal cord to the brain. Very high CSF pressure can compress this enough to cause the heart and breathing to stop.
There may be subtle problems of hand-eye co-ordination, and a degree of clumsiness which makes it difficult to perform certain tasks or do certain jobs.
Other effects of hydrocephalus include distress at everyday noises, e.g. washing machines.
Concentration and reasoning may be affected. For instance, it may be necessary to teach simple tasks like getting out of bed, dressing etc as separate, short items rather than all at once and to keep them consistent and repetitive.
Treatment Methods
There is currently no way to prevent or cure the condition. Some forms of hydrocephalus are mild and need no specific treatment. Other forms are temporary ("resolving") and do not require long-term treatment. Most forms, however, do need treatment.
The Shunt
A shunt is a device that diverts the accumulated CSF from the obstructed pathways and returns it to the bloodstream. It consists of a system of tubes with a valve to control the rate of drainage and prevent flow-back. It is inserted surgically so that the upper end is in the brain and the lower end leads either into the heart ("ventriculo-atrial") or into the abdomen ("ventriculo-peritoneal"). The device is completely enclosed so that all of it is inside the body.
In most cases, the shunts are intended to stay in place for life, though alterations or revisions might become necessary from time to time. The tube or catheter may become too short as the individual grows and an operation to lengthen it might be necessary. Occasionally, there can be mechanical failure. Also, problems can occur with blockage or infection of the shunt.
Possible signs of acute shunt blockage include: vomiting, headache, dizziness, sensitivity to light, drowsiness, fits.
Possible signs of chronic shunt blockage include: fatigue, general malaise, visuo-perceptual problems, behavioural change, decline in academic performance, just not seeming "right" to a parent or carer.
Blockages usually require an operation to adjust or replace the offending part. In shunt infections, symptoms vary with the route of drainage.
ETV
Endoscopic Third Ventriculostomy involves opening the floor of the brain using a miniaturised telescope. Because of the position of the cavities of the brain, specifically in hydrocephalus, you can navigate from the top of the skull through the brain via a natural bypass. This allows the CSF to flow freely down.
The success of treatment is determined by what caused the hydrocephalus. It is considered more suitable for obstructive ("non-communicating") hydrocephalus than for non-obstructive ("communicating") hydrocephalus. For example, if the natural outflow of fluid is obstructed by a tumour, the success rate is 85%; but when there has been an infection or a bleed in the brain the success rate is about 50%. The overall success rate of ETV in hydrocephalus is two thirds.
Sources of information
Association for Spina Bifida and Hydrocephalus (ASBAH)
42 Park Road
Peterborough
PE1 2UQ
Tel: 01733 555988
The Hydrocephalus Association
870 Market Street
Suite 705
San Francisco, CA 94102
Hydrocephalus: A guide for patients, families and friends, by C.Toporek and K.Robinson (L1074. ISBN 156592410X.) (Available to borrow from our Postal Lending Library.)