Hydrocephalus is a condition where there is a build-up of fluid on the brain. The excess fluid can put pressure on the brain, which can damage it. The damage to the brain can result in a wide range of symptoms including:
- headache,
- vomiting,
- blurred vision, and
- difficulties walking.
Cerebrospinal fluid
In the past, hydrocephalus was known as ‘water on the brain’, but this term is incorrect. The brain is not surrounded by water, but by a special fluid called cerebrospinal fluid (CSF).
CSF has three important functions:
- It protects the brain (and the spinal cord) from damage.
- It removes waste products from the brain.
- It provides the brain with the hormones it needs to function properly.
The brain is constantly producing new CSF (about a pint a day). The old CSF is released from the brain and is absorbed into blood vessels. However, if something interrupts this process, the level of CSF can quickly build up, placing pressure on the brain.
Types of hydrocephalus
There are three main types of hydrocephalus, which are listed below.
- Congenital hydrocephalus is when the condition is present at birth.
- Acquired hydrocephalus is where the condition develops after birth.
- Normal pressure hydrocephalus usually only develops in older people.
Congenital hydrocephalus
It is estimated that one in every 1,000 babies will be born with congenital hydrocephalus. The condition can be caused by birth defects such as spina bifida or as a result of an infection that the mother contracts during pregnancy, such as mumps or rubella (German measles).
Acquired hydrocephalus
Acquired hydrocephalus usually develops after a serious head injury or as a complication of a pre-existing medical condition, such as a stroke or brain tumour.
It is difficult to estimate how widespread acquired hydrocephalus is because cases are not recorded in the same way as congenital hydrocephalus. Acquired hydrocephalus is a common complication of stroke, and may affect up to 11,000 people a year in England.
Normal pressure hydrocephalus
Normal pressure hydrocephalus (NPH) is a poorly understood condition that usually only affects people who are above 50 years of age.
NPH can sometimes develop after an injury, or a stroke, but in most cases the cause in unknown. NPH is a rare condition that affects about two in every 100,000 people each year in England.
Outlook
The outlook for all three types of hydrocephalus is good. However, congenital hydrocephalus does carry the risk of long-term mental and physical disabilities as a result of permanent brain damage.
Hydrocephalus can usually be treated using a piece of equipment known as a shunt. A shunt is a thin tube that is implanted in the brain and is used to drain away excess CSF.
