Hydrocephalus is a build-up of fluid on the brain. The excess fluid puts pressure on the brain, which can damage it.
The damage to the brain can result in a wide range of symptoms, including:
Read more about the symptoms of hydrocephalus.
Hydrocephalus can usually be treated using a piece of equipment known as a shunt. A shunt is a thin tube that's surgically implanted in the brain and used to drain away the excess fluid.
Read more about how hydrocephalus is treated.
In the past, hydrocephalus was often referred to as ‘water on the brain’. However, the brain is not surrounded by water but by a special fluid called cerebrospinal fluid (CSF).
Cerebrospinal fluid has three important functions, it:
The brain constantly produces new cerebrospinal fluid (about a pint a day), while old fluid is released from the brain and absorbed into the blood vessels. However, if this process is interrupted, the level of CSF can quickly build-up, placing pressure on the brain.
Read more about the causes of hydrocephalus.
There are three main types of hydrocephalus:
These are briefly described below.
Congenital hydrocephalus is present in babies when they're born and can be caused by birth defects, such as spina bifida, or as a result of an infection that the mother develops during pregnancy, such as mumps or rubella (German measles).
Congenital hydrocephalus carries the risk of long-term mental and physical disabilities as a result of permanent brain damage.
Read more information about complications of hydrocephalus.
Acquired hydrocephalus can affect children or adults. It usually develops after an injury or illness. For example, it may occur after a serious head injury or as a complication of a medical condition, such as a brain tumour.
Read more about the causes of hydrocephalus.
Normal pressure hydrocephalus (NPH) is a poorly understood condition that usually only affects people over 50 years old.
It can sometimes develop after an injury or a stroke, but in most cases the cause is unknown.
The average age of people with NPH is 75, although it's a rare condition.
Hydrocephalus (fluid on the brain) causes slightly different symptoms depending on the type of hydrocephalus and the age of the person affected.
Babies with hydrocephalus at birth (congenital hydrocephalus) often have distinctive physical characteristics. Physical signs include:
As well as these physical signs, congenital hydrocephalus can also cause symptoms such as:
Hydrocephalus that develops in adults or children (acquired hydrocephalus) can cause headaches. The headache may be worse in the morning after waking up, as the fluid in your brain doesn't drain so well while you're lying down and may have built up overnight. Sitting up for a while may improve your headache. However, as the condition progresses, the headaches may become continuous. If hydrocephalus is not treated, it can be life-threatening.
Other symptoms of acquired hydrocephalus include:
Unlike the other two types of hydrocephalus, the symptoms of hydrocephalus that develop in older people (normal pressure hydrocephalus or NPH) usually develop slowly, over the course of many months or years.
There are three sets of distinctive symptoms. They affect:
These are discussed below.
Usually, the first noticeable symptom of normal pressure hydrocephalus (NPH) is a change in how you walk (your gait). You may find it increasingly difficult to take the first step when you want to start walking. Some people have described it as feeling as though they're frozen to the spot. You may also shuffle rather than take proper steps.
As the condition progresses, you may become increasingly unsteady on your feet. You may be more likely to fall, particularly when turning.
The change in the way that you walk is often followed by bouts of urinary incontinence, which may include symptoms such as:
The normal thinking process also starts to slow down. This can take the form of:
These may be confused with the symptoms of dementia. You may actually have mild dementia, which will improve when the normal pressure hydrocephalus (NPH) is treated.
To understand the causes of hydrocephalus (fluid on the brain), it is first useful to understand how cerebrospinal fluid (CSF) circulates through the brain.
Cerebrospinal fluid (CSF) is created in the brain. It flows through the brain through a series of chambers called ventricles.
Excess cerebrospinal fluid moves out of the brain, where it's absorbed back into the bloodstream by a specialised tissue called the arachnoid villi. The arachnoid villi act like a one-way valve. They allow excess cerebrospinal fluid to leave the brain and filter into blood vessels while preventing the blood from leaking into the brain and damaging it.
Hydrocephalus can develop if:
Congenital hydrocephalus, when a baby is born with the condition, may be the result of a brain defect that restricts the flow of cerebrospinal fluid.
These defects in the development of the brain can be caused by certain health conditions. For example, most children born with the most serious type of spina bifida will develop hydrocephalus.
Congenital hydrocephalus can also occur in babies born prematurely (before week 37 of the pregnancy). Some premature babies experience bleeding in their brain, which can block the flow of cerebrospinal fluid and cause hydrocephalus.
Other possible causes of congenital hydrocephalus include:
In many cases of congenital hydrocephalus, the cause is unknown. This is medically referred to as idiopathic.
Hydrocephalus that develops in adults or children (acquired hydrocephalus) is usually the result of an injury or illness that causes a blockage between the ventricles of the brain.
Possible causes of acquired hydrocephalus include:
It's also possible for someone to be born with narrowed passageways in their brain that restrict the flow of cerebrospinal fluid, but don't cause any symptoms until years later.
Hydrocephalus that develops in older people (normal pressure hydrocephalus or NPH) can occur after a brain injury, bleeding in the brain or infection. However, in most cases, there's no clear reason why the condition occurs.
There are several theories to explain what happens to the brain in cases of NPH. Some are outlined below.
One idea is that NPH occurs when something goes wrong with the arachnoid villi, which is the layer of tissue that allows cerebrospinal fluid to filter into the blood vessels. This means that the blood vessels don't reabsorb the fluid. This creates a gradual increase in pressure, which can cause progressive brain damage.
The exact cause is unknown, but conditions that affect blood vessels within the brain or that supply blood to the brain (cerebrovascular disease) may be linked to NPH.
The different types of hydrocephalus (fluid on the brain) can be diagnosed with brain scans.
In some cases, an ultrasound scan can detect congenital hydrocephalus before your baby is born. An ultrasound scan uses high-frequency sound waves to create an image of your womb and the baby inside.
If your baby has some of the physical characteristics associated with congenital hydrocephalus after they're born, such as an enlarged head, they may be referred for an ultrasound scan. If the results of the ultrasound are inconclusive, further testing can be carried out using:
These scans can examine the brain in greater detail. As well as showing the build-up of fluid on the brain and the increased pressure, the scans can also highlight any defects in the structure of the brain that may be causing the hydrocephalus.
Hydrocephalus that develops in adults or children (acquired hydrocephalus) can be diagnosed using a combination of CT and MRI scans. The scans can also reveal possible causes of your symptoms, such as a brain tumour.
Hydrocephalus that usually develops in older people (normal pressure hydrocephalus or NPH) can be difficult to diagnose for the following reasons:
It's important to make a correct diagnosis because, unlike Alzheimer’s disease, it's possible to relieve the symptoms of NPH with treatment.
Healthcare professionals have devised a diagnostic checklis which examines:
You may be diagnosed with NPH if you have the combination of an impaired gait, slowing of the normal mental processes and urinary incontinence, and scans have shown that your cerebrospinal fluid (CSF) is at a higher level than usual.
However, you may not have all of the symptoms in the checklist.
Further tests may also be carried out to decide whether you would benefit from having surgery, such as:
These procedures are briefly described below.
A lumbar puncture, also known as a spinal tap, is a procedure that's used to take a sample of CSF from your lower back.
A hollow needle is inserted between your back bones (vertebrae), and a small amount of the fluid is removed. The pressure of the CSF sample can then be checked.
Removing some CSF during a lumbar puncture may help to improve your symptoms. If this is the case, it's a good indication that you may benefit from treatment with surgery (see treating hydrocephalus).
If having a lumbar puncture doesn't improve your symptoms, this doesn't mean that you do not have NPH. If the lumbar puncture test is negative, you may have a lumbar drain.
A lumbar drain involves inserting a tube between your back bones to drain a large amount of CSF. This is done over a few days to see if this improves your symptoms, such as your ability to walk around. This is usually done under local anaesthetic to numb the area, or sedation to relax you.
A lumbar infusion test can also be used to help diagnose NPH and decide whether you need surgery. The procedure should be carried out under local anaesthetic so it shouldn't be painful.
The test involves slowly injecting fluid into your lower back while measuring the pressure. The additional fluid should be absorbed by your body so that the pressure stays low. However, if your body can't absorb the extra fluid, the pressure will rise. This could indicate that you have NPH and that surgery will be beneficial.
Hydrocephalus (fluid on the brain) is treated with surgery.
Babies who are born with hydrocephalus (congenital hydrocephalus) and adults or children who develop hydrocephalus (acquired hydrocephalus) usually require prompt treatment to reduce the pressure on their brain. If the hydrocephalus is not treated, the rise in pressure will damage the brain.
Both congenital and acquired hydrocephalus will be treated with either shunt surgery or neuroendoscopy (see below).
Hydrocephalus that usually develops in older people (normal pressure hydrocephalus or NPH) can also be treated with a shunt. However, experience has shown that not everyone with NPH will benefit from shunt surgery.
Due to the risks of complications occurring as a result of surgery, you will need tests to assess whether the potential benefits of surgery outweigh the risks. A lumbar drainage test or lumbar infusion test, or both, can be used to find out whether shunt surgery will benefit you. See diagnosing hydrocephalus for more information about these tests.
Shunt surgery will be recommended if testing reveals that it would be beneficial.
Shunt surgery involves implanting a thin tube, called a shunt, in the brain. The excess cerebrospinal fluid (CSF) in the brain runs through the shunt to another part of the body, usually the abdomen. From here the fluid is absorbed into your blood stream. The shunt has a valve inside it to control the flow of CSF and to ensure it does not drain too quickly. You can feel the valve as a lump under the skin of your scalp.
Shunt surgery is carried out by a neurosurgeon (a specialist in surgery of the brain and nervous system). You will be given a general anaesthetic before the operation so that you will be asleep throughout the procedure, which usually takes one to two hours.
After the operation, you may need to spend a few days in hospital to recover. If you have stitches in the wound in your head, they may dissolve on their own, or you may be advised about when these will be removed. Some surgeons use skin staples to close the wound. Like stitches, these will need to be removed after a few days.
Once the shunt has been installed, further treatment for hydrocephalus may be required if the shunt becomes blocked or infected. Shunt repair surgery will then be necessary. See complications of hydrocephalus for more information.
An alternative procedure to shunt surgery is an endoscopic third ventriculostomy (ETV).
ETV involves making a hole in the floor of the brain, allowing the trapped CSF to escape to the surface of the brain where it can be absorbed, instead of inserting a shunt.
An ETV is not suitable for everyone. However, it could be a possible treatment option if the build-up of CSF in your brain is the result of a blockage (obstructive hydrocephalus). The CSF will be able to drain through the hole, avoiding the blockage.
You are first given general anaesthetic before the operation. The neurosurgeon will then make a small hole in your skull and use an endoscope to look inside the chambers of your brain. An endoscope is a thin, long tube that has a light and a video camera at one end. A small hole will be made inside your brain with the help of the endoscope. After the endoscope has been removed, the wound will be closed using stitches. The procedure takes around one hour.
There is less risk of an infection developing after an ETV than with shunt surgery. However, as with all surgical procedures, there are some risks associated with ventriculostomy (see complications of hydrocephalus).
The long-term results for treatment with ETV are very similar to those for a shunt operation. As with shunts, ETVs may block months or years after surgery, resulting in your symptoms reoccurring.
Hydrocephalus (fluid on the brain) can cause complications, or complications may develop as a result of surgery used to treat it.
A shunt is a delicate piece of equipment prone to malfunction, usually through blockage or infection. It's estimated that up to 4 out of 10 shunts will malfunction in the first year after surgery. Sometimes a scan carried out after the operation shows that the shunt isn't in the best position, and that further surgery may be needed to reposition it.
If a baby or child has a shunt fitted, the shunt may become too small as your child grows, and it will need to be replaced. As most people need to have a shunt for the rest of their life, more than one replacement may be needed.
It's estimated that most children with hydrocephalus may have an average of two procedures for shunt problems before they're 10 years old.
Occasionally, when shunt tubes are positioned, bleeding can occur. This can result in nerve problems, such as weakness down one side. There's also a small risk of seizures (fits) following any surgery on the brain.
In younger children, particularly babies, cerebrospinal fluid (CSF) can run alongside the shunt rather than down it, and it can leak through the skin wound. If this occurs, further stitches will be needed to stop the leak.
A shunt blockage can be very serious because it can lead to an excess build-up of fluid on the brain, which can cause brain damage. This will cause the same symptoms of hydrocephalus, such as:
In babies, you may notice their head growing larger or they may have a bulging or tense fontanelle (the soft spot on the top of their head).
Contact your care team immediately if you or your child have these symptoms. Emergency surgery will be required to replace the malfunctioning shunt.
Shunt infection is also a relatively common complication. The risk of infection can be around 3-15% and is more likely to occur during the first few months after surgery.
The symptoms of a shunt infection may include:
Contact your care team immediately if you or your child has these symptoms. You may need a course of antibiotics to treat the infection and, in some cases, surgery may be required to replace the shunt.
An endoscopic third ventriculostomy (ETV) is a surgical procedure where a small hole is made in the floor of your brain. Complications can occur after this type of surgery, such as:
If there's a problem with the hole, it may be possible to repeat the procedure, or you may need to have a shunt fitted (see treating hydrocephalus).
Other risks of ETV include nerve problems, such as weakness down one side of the body, double vision or hormone imbalances. Most nerve problems will get better, but there's a small risk of permanent problems. There's also a small risk of epilepsy, and a very small risk of an injury to one of the blood vessels in the brain, which may be fatal.
Many babies born with hydrocephalus (congenital hydrocephalus) have permanent brain damage. This can cause a number of long-term complications, such as:
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.