The pressure inside the skull is caused in part by the production of the CSF and in part by the pressure of the blood being pumped to the brain. As the CSF pressure increases, it will interfere with the brain's blood supply. This will deprive it of the oxygen and the glucose it uses to function. Lack of these two elements will cause irritability, tiredness, and drowsiness. If the pressure is not released, loss of consciousness will occur as the brain functions slowly shut down.
If the CSF pressure is normalized quickly, no damage may have been done, but the pressure increase often goes unnoticed for some time before it is diagnosed. During this time, the loss of blood being supplied to the brain will lead to damage to the blood vessels in the brain
The following stage involves irreversible damage to the brain cells; the areas most affected are usually those linked to learning, coordinated movement, and even thought.
Papilloedema may occur, which is a physical problem of eyes. If untreated, the CSF pressure pressing on the blood supply to the eyes can cause damage to the optic nerves and result in blindness.
Another aspect of the pressure to the nerves associated with the eyes is a condition referred to as the "sunset eye sign". This is when the eyes are stuck in a downwards position and it is most common in babies.
As vital functions are controlled from the brain stem, a very high CSF pressure can lead to problems with the heart and breathing. However, this is uncommon as the raised pressure is usually treated before this stage.
In cases where damage to the brain has occurred, there can be a number of effects. The precise effects are different from person to person, and they are affected by individual abnormalities as well as by the pre-existing degrees of ability and personality. Learning disorders are common amongst those with hydrocephalus, but their exact effects vary considerably. Much is said and written about intelligence, and particularly about IQ (intelligence quotient), in people with hydrocephalus.
There may be subtle problems of co-ordination of hand movements, with what the person sees, as well as a degree of clumsiness, which make it difficult to perform certain tasks or do certain jobs.
Other effects of hydrocephalus which are more difficult to explain may also be seen. For instance, some people are very seriously distressed by everyday noises such as vacuum cleaners or washing machines.
Seizures are experienced by about one third of people with hydrocephalus at some point in their lives. This can be in relation to shunt revisions or due to a rise in intercranial pressure. They can be isolated incidents although, if epilepsy is developed it will be treated with anti-convulsive drugs, just like for people without hydrocephalus.
Visual perception may be a problem, leading to difficulties understanding position and relationship of objects. There can be problems with depth perception, judging distance, or speed.
Problems with identifying difference between shapes will affect reading and writing. There can also be problems understanding shape, size, direction, volume, and position of objects.
Visual perception difficulties can consist of problems with judging slopes, height of kerbs, width of doors, or the space in a room. The effects of hydrocephalus can include:
All of these have major implications for adult life.
There may be real problems with concentration and reasoning which require a sympathetic but skilled approach. For instance, simple everyday tasks such as getting out of bed, washing one's face, and dressing oneself, will often have to be taught as separate, short term items (as opposed to all at once) and kept consistent and repetitive.
Damage to the nerves in the brain, which normally allow us to learn complex series of actions very quickly, may result in difficulties in learning which are unrelated to intelligence. Much can be done to help, and professional advice should be sought whenever needed.
There may be a difference in the ability to understand and to use language. The child may have a good vocabulary due to mimicry, but may give inappropriate answers due to a limited understanding of these words.
Psychological development in children and adolescents with hydrocephalus may proceed normally, but sometimes the changes associated with puberty (breast development, body hair growth etc.) appear much earlier than expected. The intrusion of psychological aspects of sexual development into a mind which is emotionally still very immature can cause distressing problems. Again, specialist advice should be sought if necessary.
People with hydrocephalus generally score better on verbal tests than on performance tests, this is thought to reflect the distribution of nerve damage in the brain. Certainly during periods of rising CSF pressure, such as in untreated cases or when a shunt is blocked, the effect on performance IQ is more significant.
Generally speaking, people who have had hydrocephalus since birth or childhood have, as a group, a lower average IQ than a comparable group without hydrocephalus. However, it is important to realise that there is a wide range in each group, and some people with hydrocephalus have very high scores.