Know Your Shunt 

Life with a new shunt can bring several challenges. Knowing your shunt, how it works, and what type you have can be very important. You may need MRI scans in future, or you might want to travel. This will be simpler and less stressful if you know the type of shunt you have, and what precautions, if any, are advisable. Your neurosurgical team will be able to give you information on your shunt make and model, and any other information you might need. Your GP may also be able to help. 

What is a shunt? 

A shunt is the main method for treating hydrocephalus, and can be used for certain other conditions, like IIH or arachnoid cysts. It is a thin, flexible silicone tube which carries excess fluid (CSF) from the head or spine to another part of the body. This allows the CSF to be either absorbed by the body or removed into the bloodstream.  

There are five main areas of the body shunts are placed: 

  • Ventriculo-peritoneal (VP) -from the ventricles to the peritoneal space, in the abdomen 
  • Ventriculo-atrial (VA) - from the ventricles to the right atrium of the heart 
  • Lumbar-peritoneal (LP) – from the spine to the peritoneal space, in the abdomen 
  • Ventriculo-pleural (VPl) – from the ventricles to the pleural space, around a lung 
  • Ventriculo-subgaleal (VSG) – from the ventricles to the scalp 

The most commonly used shunts are VP and LP shunts with VA and VPl generally used when a VP shunt is not appropriate or repeatedly fails. VSG shunts are used in very small and premature babies, when they are too small for a VP shunt.  

How do shunts work? 

Shunts have four main parts. These are listed in the order they would be inserted starting from the ventricle/spine: 

  • Proximal catheter 
  • Reservoir 
  • Valve  
  • Distal catheter 

The part of the shunt that is inserted into the brain’s ventricles (or lumbar spine in LP shunts) is called the proximal catheter. The part of the shunt from the valve to the abdomen, heart, pleural space, or scalp is called the distal catheter. These tubes are usually made of thin silicone. Some shunt tubing may also have antibiotics built into the tubing to reduce the chance of infection (Bactiseal shunts). 

The shunt reservoir, which feels like a bump below the skin, holds a small pocket of CSF which is drained directly from the ventricles. This pocket can be used to get a sample of CSF when there is concern about infection and can also provide information if a shunt blocks. A reservoir that does not fill after being pressed points towards a blockage in the proximal catheter and a reservoir that is difficult to press points to a blockage in the distal catheter. It is important not to push on your reservoir unless instructed by your neurosurgeon. You may accidently press it when you wash your hair, for example, and this should not cause any problems, but constant and repeated pressing on the reservoir can cause your shunt to over drain or even block. Some newer reservoirs contain a sensor that your neurosurgeon can use to measure your intracranial pressure without the need for a lumbar puncture and can help guide any adjustments or further treatment options. 

The valve ensures the shunt only drains when the pressure in the head reaches a certain level. There are many different types of valves made by different manufacturers, and it is important to know what valves you have. Each surgeon has their own preferred valve type and the type you will receive will also be the most appropriate for you. Some people may also hear their valve opening when it is under the scalp as a short buzz, but this is not the case for everyone. 

In some cases, a valve and/or reservoir may not be used, for example the VSG. 

Types of Shunt Valve 

Fixed pressure 

In some cases, the valve will be ‘fixed.’ This means that the setting of the valve cannot be changed and if an adjustment is needed later for over- or under-drainage, the valve must be replaced.  


A programmable valve can be adjusted to open at various pressures, in clinic appointments without the need for surgery. They are adjusted using a special tool, made by the valve manufacturer, and this is generally very quick and easy. Programmable valves are not usually adjusted in the first 6 weeks following the insertion of a shunt to allow the swelling and wounds to heal first. 

In other cases, two valves may be used. Each will be set to a different pressure setting and are designed to work together to prevent over drainage when you are sat up or standing up and to drain when you are lying down.  

Gravitational units 

These can be added to the shunt, or included in the design of some shunts, to help prevent over drainage. 

What can affect the way shunts work?  

Shunts work well for most of the time but there are certain situations where they do not work as effectively. One example of this is when you are lying down as this will remove the effect of gravity. A shunt works by allowing CSF to drain from an area of high pressure to an area of lower pressure. When you lie down, your head and your abdomen have little difference in height, so the pressure difference is likely to be less.  If you find you are groggy or have head pain in the mornings, try sleeping with extra pillows, or propped up a little. 

Another position that causes shunts to work less effectively is bending over. This increases the pressure in your abdomen so reduces the difference in pressure between your head and abdomen. CSF will not drain uphill in your shunt so it is important to try to keep your head higher than your abdomen. 

If you gain weight, especially in the abdomen, your shunt may work less well and may need adjusting to allow it to drain more CSF, as the pressure inside the abdomen increases. If you lose weight, you may need your shunt adjusting to reduce over-drainage. 

If you are constipated or drink an excessive number of fizzy drinks, this would cause your bowel or stomach to enlarge. This will take up more space in your abdomen leaving less room for the CSF to drain into. If you experience long term constipation, speak to your GP (General Practitioner) or specialist bladder and bowel nurse for support, which may include diet changes or laxatives.  

Exercise and shunts 

Exercise is very important for your general health and fitness and most sports are suitable for people with shunts. However, strenuous exercise increases the blood supply to the brain which will increase your intracranial pressure for a time, and your shunt will drain more fluid. Exercises that involve having your head below your abdomen (e.g., certain gymnastic moves) will stop your shunt from working whilst you are in this position. It will also increase your intracranial pressure, so this is best avoided. Contact sports and martial arts may be not advisable, but it is important to check with your neurosurgeon. People with LP shunts should avoid anything that would require twisting at the waist, such a golf as this may dislodge your shunt.  

Why knowing your shunt matters 

It is important to know what type of shunt you have and what valves you have. Complications can vary between shunt types and so here is some advice on what to look out for or avoid.  

MRI Scans 

One reason it is important to know what shunt you have is in case you need to have an MRI scan. Fixed pressure valves are fine, but some types of programmable valves may have the setting altered by the powerful magnets in the scanner and need to be checked and sometimes reset after the scan. This can only be carried out by your neurosurgical team, who have the special tool for adjusting the valve setting. The MRI team need to be sure you can have your scan without your shunt being affected, or that arrangements have been made to have the setting checked straight afterwards. 

Even if you have had a scan at another hospital before, you will be asked about your shunt again as each scanner is different. If you attend any hospital which is not your neurosurgical hospital, they will not have your notes or know what shunt you have. They will need to confirm your shunt type with your neurosurgical team and your scan could be delayed, cancelled, or rebooked. In an emergency, a CT scan may be used instead of an MRI if the hospital cannot confirm what shunt you have, but CT scans give different information to MRIs and may not be as appropriate. 

There are several types of programmable shunt which are designed so they cannot be reset by the MRI scanner (MRI-safe) so do find out what shunt you have, if you don’t know already.  


Fixed pressure shunts are completely unaffected by magnets. Several of the newer types of programmable shunts have been designed so they can’t be inadvertently reset by magnets in the environment. If your valve is suitable to be in an MRI scanner, you should not be concerned about magnets in household objects or security scanners. 

There have been a few anecdotal reports of some programmable shunts being accidentally reset by magnetic fields, but magnetic fields weaken the further you are from the source (ie the magnet). In schools, the use of bar magnets in science lessons should not pose a risk to these valves so long as they are not held against the valve area. Induction cooking hobs are also unlikely to cause any problems. Most shunt valves should not be affected by magnetic airport security scanners as the magnetic fields they produce are too low to penetrate the skin, but there have been a few anecdotal cases of this, and many people with shunts are anxious about this aspect of travel. Many airports are introducing X Ray or millimetre wave Whole Body Scanners, which do not use magnets, and are suitable for all people with shunts. 

There have been a few cases of some types of headphones adjusting some valves which is why it is important to check what type of valve you have.  

The chance of unintentionally changing the settings on shunt models that are less resistant to magnets, rapidly reduces the further the valve is from the magnet.  

Here are some general tips when using magnets with a programmable shunt that is not one of the magnet-resistant models:  

  • keep electronic devices at least 5cm/2 inches from the shunt valve 
  • supervise young children using electronic devices 
  • hold your phone on the opposite side of your head to your valve. 

Also, make sure you know where your valve is located under the skin. This may be on the head or in the neck area. It shouldn’t be confused with the reservoir (the prominent bubble on the head)  

It is important that you find out what shunt you have so you do not worry about your shunt and continue to enjoy the things you love. 

How to find out about your shunt  

To find out about your shunt, the best people to ask are 

  • your neurosurgical team 
  • your specialist hydrocephalus nurse 
  • your neurosurgeon’s secretary. They can check the operation notes and hospital records for you. 

You can also check with your GP surgery as this information should be included in the Discharge letter from hospital, when you go home. You can check your records yourself online through apps such as Patient Access or NHS (National Health Service) App although these may not contain everything you need to know.  

Shunt Alert Cards  

It is important to have a record of what shunt you have and your medical condition. SHINE has a shunt alert card, which any member with a shunt can apply for. Fill in the card with your shunt information, or ask the neurosurgical team to fill it in for you when you have your shunt operationand carry it with you when you leave the house in case of emergencies. This is particularly important if your nearest hospital is not your neurosurgery hospital as they may not know about your shunt.  

It is also important to have details for your next of kin and your specialist team’s contact details to be used in an emergency.  

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