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This page provides information about the WEB device and how it is used to treat cerebral (brain) aneurysms. It is intended for use by patients (or their families and carers) in whom treatment with a WEB device has been proposed.

If you have any questions about the WEB device, or would like further information about cerebral aneurysms, please do not hesitate to contact a member of the team caring for you or a member of the neuroradiology team, who will be happy to answer them for you.

A WEB device is a basket, made of very fine wire mesh. It acts as a plug within the aneurysm, reducing the blood flow within it and preventing any further bleeding (see Figure 1). Intracranial coils are the usual method used to pack the aneurysm. However, some aneurysms are difficult to pack due to their shape.

Sometimes we use stents (a wire tube which lines the vessel wall) to hold the coils within the aneurysm, but this requires the patient to take medication to thin their blood for an extended period of time after. The WEB device allows the aneurysm to clot off without coils or stents.

The aim of the WEB device is to prevent blood from entering the aneurysm and therefore prevent the risk of it bursting. It allows us to successfully treat large, wide-necked aneurysms which may be difficult to treat with coiling alone.

All treatments and procedures carry risks and we will discuss the risks of using a WEB device with you. Each case carries a different risk and we will try to estimate your personal risk in our discussions with you prior to your treatment. The procedure will take place under a general anaesthetic. Your anaesthetist will discuss the risks of general anaesthesia with you. It is important to tell your doctor if there is a possibility you may be pregnant.

Problems that may happen straight away

During your procedure a contrast agent will be injected into to the arteries to visualise the aneurysm for treatment. Contrast agents are safe drugs; however as with all drugs, they have the potential to cause an allergic reaction. The department is equipped to deal with reactions in the rare event of this happening. If you have known hyperthyroidism, previous kidney problems or kidney failure or are currently taking a medication called metformin, please contact neuroradiology prior to your treatment, as we may need to provide you with further instructions before having a contrast enhanced procedure.

Problems that may happen later

You may experience some headaches or tiredness following your procedure. These are quite common after aneurysm treatments, probably due to clotting inside the aneurysm as part of the healing process and may go on for some time. A mild painkiller, rest and drinking plenty of water will help. We will give you pain medication to help. You may be at a higher risk of bleeding than normal.

You will need to take tablets to make the blood thinner and less likely to clot in the days leading up to the procedure and for many months afterwards. These tablets can increase the risk of bleeding in other areas of the body and can irritate the stomach. It is important to tell your consultant if you have had a stomach ulcer in the past. The contrast agent used during a WEB device treatment is iodine based contrast and is excreted through the kidneys; this may affect your kidney function. You will have a blood test to test your kidney function beforehand to ensure it is safe for you to have contrast. The risk of you having contrast will be weighed against the benefit of having this treatment and is decided by the team referring you.

For further information on the use of iodine based contrast agents please see the information leaflet ‘Contrast Agents for X-ray, Fluoroscopy, CT and Angiography Examinations: An Information Guide’.

Problems that are rare, but serious

Whilst serious complications remain very unlikely, there are some risks evident. Like all procedures involving the blood vessels of the brain, the placement of a WEB device carries a small risk of stroke. This can range from a minor problem which improves over time to a severe disability involving movement, balance, speech or vision or may even be a threat to life. On our current evidence, we would estimate that about 5 people in 100 will experience these problems.

Any problem is usually apparent during or immediately after the procedure, or during the next few days whilst you are still in hospital. Haematoma, bruising or vessel damage around the groin/ arm puncture site may also occur. Usually a stitch is placed in the femoral (in the groin) or radial (in the arm) artery after the tube has been removed. Often there is bruising and sometimes bleeding in the groin or arm. It is rarely serious but can go on for a few hours.

Very occasionally there is damage to the blood vessel requiring a further surgical operation. You will need to be monitored carefully in hospital for the first few days to control your blood pressure and blood clotting.

Radiation risk

The use of X-rays during the procedure presents a very small risk of hair loss, skin erythema (reddening) or very rarely the development of cancers in the future. Our state of the art imaging equipment and modern techniques ensure the radiation dose is as low as possible. In addition, your doctor will have made a judgement about your risk and benefit before agreeing to the procedure (including the risk to your health of not having the procedure).

Patients of child bearing capacity between the ages of 12 and 55 years are required by law to be asked about possible pregnancy when undergoing examinations involving X-ray. Patients who either are, or think they may be pregnant must inform the neuroradiology department as soon as possible.

In some urgent cases the scan may still go ahead but with additional precautions in place. To reduce the risk for early and unknown pregnancies, WEB treatments are usually performed within the first ten days of the menstrual cycle when pregnancy is much less likely. The interventional neuroradiologist performing the procedure will discuss all possible risks with you and give you the opportunity to ask questions.

Your case will have been discussed by a multidisciplinary team of interventional neuroradiologists, neurosurgeons and neurologists. The treatment offered is based on the agreement of the team as to what is the best course of action. It is important that you fully understand the procedure, what it means for you and any alternative treatments available. You are under no obligation to follow the advice given.

If you are unhappy about the treatment being offered, a full discussion with members of the team can be arranged. It is entirely reasonable to seek a second opinion if you still have concerns. Whatever decision you reach it will not affect the standard of care you receive. We will continue to offer you the best care possible, based on the best current evidence we have available.

There are several options available for the treatment of aneurysms. However the location, size and shape of the aneurysm can dictate which treatment is the safest. It is likely that these other treatments will be considered as higher risk than the treatment offered. Your consultant or a senior member of their team will talk through all options with you.

Alternative treatments for cerebral aneurysms include:

Conservative treatment

On occasion, treatment consists of clinical follow-up and Magnetic Resonance Imaging (MRI) or Computerised Tomography (CT) scans. This is done in conjunction with blood pressure control and advising on any appropriate lifestyle changes (such as giving up smoking). This option carries a risk of the aneurysm bleeding or causing other problems in the future.

Surgical treatment

Some aneurysms can be treated surgically by placing a metal clip across the neck of the aneurysm (narrow part of the aneurysm), this is called ‘clipping’. This procedure is performed under a general anaesthetic and involves opening the skull to reach the aneurysm.

Other Radiological Techniques

More commonly, aneurysms are treated by passing a catheter (fine tube) through the blood vessels and ‘packing’ the aneurysm from the inside with very fine metal coils (coiling). This may be difficult due to the size of the aneurysm or its neck.

You will be given a course of anti-platelet medication for 5 days prior to your WEB device treatment. This course will involve taking oral aspirin and prasugrel, which are used to thin the blood, these are given to reduce the likelihood of your blood clotting and potentially causing a stroke, during or shortly after the procedure. The neurovascular clinical nurse specialists will contact you before your treatment to advise on these medications. You should take all your other medications as normal, unless advised otherwise.

You will be asked to arrive at the hospital the day before or on the morning of your procedure. If you are arriving the morning of your procedure you will be asked to arrive at 8am to the surgical reception unit (SRU) or to the ward specified by the admission officer in contact with you. Your procedure may take place at any time during the day due to emergency cases, but we will endeavour to keep you informed and perform your procedure as early in the day as possible.

The procedure is performed by specialist doctors called Interventional Neuroradiologist (INR). The INR will see you on the ward to explain the procedure and any associated risks. Please feel free to ask any questions at this time. The procedure is performed under a general anaesthetic (this means you will be unconscious or ‘asleep’ throughout). Your anaesthetist will talk to you about the anaesthetic, pain relief and what you can expect when having a general anaesthetic both in clinic before the procedure and again briefly on the ward the day of your procedure.

You will need to fast for six hours before your procedure. Your anaesthetist will confirm with you a specific time you must stop eating and drinking. You should still take all of your medications at the normal times throughout this period with a sip of water.

A member of staff, usually the nurse caring for you, will accompany you to the neuroradiology department.

We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with a contrast scan or procedure, by law we must ask for your consent. This confirms that you agree to have the procedure and understand what it involves.

Staff will explain all the risks, benefits and alternatives before they ask you to consent to contrast. If you are unsure about any aspect of your proposed scan or procedure, please don’t hesitate to speak with a senior member of staff again.

You will be given a general anaesthetic in the anaesthetic room prior to transfer to the angiography suite. The procedure is performed by an INR in the angiography suite (operating theatre) located in the neuroradiology department. It usually takes between one and three hours. A dedicated team of radiologists, radiographers, anaesthetists and nurses will be in the angiography suite. They will be monitoring you closely throughout the procedure.

Once the procedure has commenced, the INR uses X-ray guidance to place a thin, flexible plastic tube (catheter) into the femoral (in the groin) or radial (in the arm) artery. The catheter passes through the main artery in the body called the aorta and finally into an artery supplying the brain.

A second smaller catheter is inserted inside the first. The second catheter goes into the aneurysm. The WEB device is pushed through this catheter and into the aneurysm. This usually reduces the amount of blood getting into the aneurysm immediately. Sometimes it is necessary place a few WEB devices if the aneurysm is very large to get the best results.

Once the INR is satisfied with the result, the catheters are removed and the blood vessel in the groin or arm is sealed with a stitch.

After the procedure you will spend some time in the recovery unit or high dependency unit (HDU) before being transferred back to your ward. These units provide a high level of monitoring. You can expect to remain in hospital for a minimum of four to five days after the procedure, until you are walking around and feeling back to normal. You should plan to take some time off work, at least a week or two and you should arrange to have someone to stay with when you first return home.

Everyone is different and people recover from these procedures at different rates. You may experience some pain or bruising at your groin or arm, depending where the catheter was placed, this should reduce over a few days.

It is also common to experience headaches in the days or weeks following the procedure. This is related to the aneurysm shrinking. You will be given pain killing drugs to help. If this headache becomes severe or you experience nausea, vomiting, drowsiness or severe stiffness in your neck go immediately to your nearest Accident and Emergency Department (A & E, Casualty) where a CT scan will be performed.

For any non-urgent questions or concerns you may have following your procedure, please contact the neurovascular nurse specialists.

The Brain & Spine Foundation UK
0808 808 1000

UCLH cannot accept responsibility for information provided by other organisations.

  • KLISCH, J., SYCHRA., VOJTECH, S., STRASILLA, C., LIEBIG, T. AND FIORELLA, D. 2011. The Woven endobridge cerebral aneurysm embolization Device (WEB II): Initial clinical experience. Neuroradiol, 53, 599-607.
  • DING, Y., LEWIS, D.A., KADIRVEL R., DAI D. AND KALLMES, D.F. 2011. The Woven EndoBridge: a new aneurysm occlusion device. Am J Neuroradiol., 32:607-11.

Lysholm Department of Neuroradiology,
National Hospital of Neurology and Neurosurgery,
Queen Square,
London WC1N 3BG 15

Direct line: 020 344 83444
Switchboard: 0845 155 5000/ 020 3456 7890
Extension: 83444/ 83446
Fax: 020 344 84723

Neurovascular Clinical Nurse Specialists
National Hospital for Neurology and Neurosurgery
Queen Square
London WC1N 3 BG

Direct line: 020 344 83523
Switchboard: 0845 155 5000/ 020 3456 7890
Extension: 83523

The Lysholm Department of Neuroradiology reception is located in Chandler Wing, on the lower ground floor of NHNN, Queen Square. Please turn left when you exit the Chandler Wing lifts on the lower ground floor to find our main departmental reception.

Page last updated: 29 May 2024

Review due: 01 March 2025