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.

Symptoms of hydrocephalus

Acquired and idiopathic forms of hydrocephalus can occur at any time in life and typical symptoms include:

  • Headaches
  • Neck pain
  • Nausea
  • Vomiting
  • Drowsiness
  • Confusion
  • Poor co-ordination
  • Blurred or double vision
  • Difficulty walking
  • Bladder and/or bowel incontinence

The symptoms of normal pressure hydrocephalus may appear slowly over months or years. These include:

  • A change in the way you walk
  • Urinary symptoms, including a frequent and urgent need to urinate, and loss of bladder control
  • Changes in mental abilities, including slower reactions and information processing

Symptoms of congenital hydrocephalus tend to appear early in childhood and include unusually large head, muscle spasms, poor feeding, irritability and drowsiness.


There are a number of different treatments and diagnostic tests for hydrocephalus. MRI or CT scans can show signs CSF build-up, such as enlarged ventricles. Brain scans can also help doctors determine the cause of hydrocephalus, and rule out other possible reasons for the symptoms.

Other commonly used diagnostic tests include eye tests to check vision and look for swelling behind the eyes. Lumbar punctures are also performed to examine the CSF and check pressure levels.


Initial treatment for hydrocephalus focuses on reducing pressure on the brain, and restoring the normal flow of cerebrospinal fluid.

A shunt is usually used to drain excess CSF from the brain. A shunt is a small tube that is implanted in the brain and runs to another part of the body, usually the abdomen, where the CSF can be absorbed into the blood stream.

There are a number of other treatments that doctors may explore.

Long term effects

If hydrocephalus causes damage to the brain, the symptoms may be similar to other types of acquired brain injury. Rehabilitation may be beneficial to help regain independence and maximise recovery.

The effects of brain injury section gives you more detailed information about acquired brain injury and guidance on how to manage the symptoms.

My story

"People living with hydrocephalus feel left in the dark"

42-year-old Shana Lewis, from London, had been running her own cake business and enjoying life as a loving mother and family woman when she was diagnosed with hydrocephalus.

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