Hydrocephalus is caused by a buildup of fluid inside the skull, which can increase pressure and cause damage to the brain. This section explains the causes and symptoms of hydrocephalus as well as outlining the long-term effects and treatment options available.
The brain and spine are surrounded by cerebrospinal fluid (CSF), which is essential for cushioning the brain, providing nutrients and removing waste products.CSF is mainly produced in the choroid plexus and flows around the sub-arachnoid space surrounding the brain and spinal cord. It then passes through a series of chambers in the brain called ventricles and connecting channels called foramina.We produce about a pint (500ml) of CSF per day but the brain can contain only about 120-150ml. For this reason excess CSF is drained into the bloodstream through a series of valves called the arachnoid villi. The CSF is recycled about three times a day.
Hydrocephalus can occur if the flow of CSF is blocked, if the body produces too much CSF, or if there is a problem with the arachnoid villi which stops CSF being absorbed into the blood. This can cause the ventricles and sub-arachnoid space to swell as the fluid pressure increases, which may lead to permanent brain injury if prompt treatment is not received.
Types of hydrocephalus
There are five main types of hydrocephalus:
- Communicating hydrocephalus occurs despite the fact that there is no obvious blockage or obstruction in the flow of CSF. The term non-obstructive hydrocephalus is also used. It occurs when the reabsorption of the CSF into the bloodstream is impaired, resulting in increased CSF pressure and enlarged ventricles.
- Non-communicating hydrocephalus occurs when there is a blockage in the flow of CSF. It is also known as obstructive hydrocephalus.
- Hydrocephalus ex vacuo is the result of the ventricles enlarging to compensate for loss of brain tissue. This can happen as a result of another form of acquired brain injury, such as a stroke or traumatic injury.
- Arrested hydrocephalus can occur in people who have a minor blockage in the CSF flow. The person may suffer no effects because the CSF production is balanced by absorption and so pressure is normal. However, if the balance is disrupted spontaneously, or after a minor head injury, then the resulting increase in CSF pressure is called arrested hydrocephalus.
- Normal pressure hydrocephalus (NPH) affects older people (average age 70-75) and is often categorized as a form of dementia. This type of hydrocephalus can be difficult to diagnose because it develops over a long period of time so the fluid pressure in the brain may not appear to be high. It can develop after brain injury but in most cases the cause is unknown.
Causes of hydrocephalus
The different types of hydrocephalus can be congenital, acquired or idiopathic.
- Congenital hydrocephalus – When hydrocephalus is caused by congenital birth defects the symptoms normally present themselves in childhood. However, they may not appear until adulthood in some cases.
- Acquired hydrocephalus – Hydrocephalus can be acquired at any stage of life due to head injuries, strokes, tumours, meningitis, hemorrhages and other forms of ABI.
- Idiopathic hydrocephalus – This means that there is no known cause and many cases of hydrocephalus, at any stage of life, appear despite no apparent obstruction or impairment of CSF reabsorption.