Unruptured aneurysm

I have an aneurysm. Does it need to be treated?

Not necessarily.

Aneurysms can be dangerous but some require no treatment at all. The decision to treat is often a complex one and requires discussion with an experienced medical professional. Any medical treatment involves a degree of risk, no matter how small. It is probable that for certain low-risk aneurysms the risk of the aneurysm is outweighed by the risk of the treatment.

For brain aneurysms there are generally three management strategies:

1. No treatment: a period of observation may be undertaken to ensure the aneurysm is not growing or changing.
2. Endovascular treatment. This involves treating the aneurysm through the blood vessels. Generally, a small incision is made in the groin or wrist and a very thin tube is directed, under X-rays, into the aneurysm. Through this tube tiny coils and stents can be inserted to block off the aneurysm. This is less invasive than surgical treatment.
3. Surgical clipping. This is an operation involving temporarily removing some of the skull bone (‘craniotomy’) to access the aneurysm and place a clip around its neck. It is by nature more invasive than endovascular treatment. As the brain is very delicate this procedure is carried out with the use of an operating microscope.

There are no medications that can be given to shrink aneurysms, however stopping smoking and controlling blood pressure if it is high can reduce the risk of it rupturing.

What factors might lead to an aneurysm being treated?

• Symptoms: If the aneurysm is causing symptoms such as double vision or headaches. This is uncommon, however, as most aneurysms do not cause symptoms.
• Location: Aneurysms located in certain parts of the brain are more dangerous than others. This includes aneurysms within the ‘posterior’ circulation, which includes the basilar, vertebral, and posterior cerebral arteries.
• Size: Larger aneurysms are more likely to rupture. This rule does not hold universally true, however, as it is not uncommon to see ruptured smaller aneurysms.
• Shape: Aneurysms with an irregular shape have been associated with increased rupture rates.
• Previous aneurysm rupture: If the aneurysm has previously ruptured, or the patient has other brain aneurysms which have bled before, then treatment is more likely to be recommended.
• High blood pressure: Blood pressure should be controlled in patients with aneurysms as it predisposes aneurysms to rupture.
• Smoking: Aneurysms are more likely to rupture in people who smoke and cessation is recommended if possible.

What does endovascular treatment involve?

Endovascular treatment is a minimally invasive procedure to treat aneurysms. Rather than requiring a large incision and direct surgical access to the aneurysm, endovascular treatment achieves its goal by guiding small, specialized devices through the patient’s blood vessels to the site of the aneurysm. Embolisation means to promote clot formation within the aneurysm, commonly by inserting platinum coils or placing stents of flow diverters acoss its neck. These techniques seal off the aneurysm, preventing blood from entering it.

What are the types of endovascular treatment?

1. Coiling (Endovascular Coiling or Coil Embolization). Coiling is a method where small, soft platinum coils are threaded through a catheter and placed directly into the aneurysm. The aim is to initiate a blood clotting process that fills the aneurysm with a stable clot. This effectively isolates the aneurysm from your blood circulation, reducing the risk of rupture.
2. Stent-Assisted Coiling. Stent-assisted coiling uses a small, tube-shaped device called a stent in conjunction with coiling. The stent provides support to the weakened arterial wall and helps keep the coils within the aneurysm sac. This method is often used when the aneurysm has a wider neck or irregular shape that makes regular coiling challenging. The stent remains in the artery permanently.
3. Flow Diversion. Flow diversion is a treatment method that uses a device called a flow diverter, similar to a stent but denser. It’s placed in the artery carrying blood to the aneurysm. Instead of filling the aneurysm with coils, the flow diverter redirects blood flow away from the aneurysm. This reduced blood flow into the aneurysm promotes clotting within the aneurysm, leading to its closure. Flow diverters may also be used with coils although this is less necessary.
4. Intrasaccular devices such as Woven Endobridge (WEB). Intrasaccular devices are a newer development in aneurysm treatment. These devices are placed directly into the aneurysm sac via a catheter, similar to coiling, but are able to treat aneurysms that would otherwise require stents.

What is coil embolisation?

Coil embolisation, also known as endovascular coiling, is a procedure to treat brain aneurysms. The process is minimally invasive and is a proven technique to prevent the rupture of the aneurysm.

The procedure starts with the patient being placed under general anesthesia so that they do not experience any pain during the operation. The doctor then makes a small incision, typically in the wrist or groin, to access a blood vessel. Following this, the doctor inserts a long, thin tube, called a catheter, through the incision into the blood vessel. Using a method called fluoroscopy, which involves real-time X-ray imaging, the doctor is able to navigate the catheter through the patient’s vascular system until it reaches the blood vessels of the brain where the aneurysm is located.

Once the catheter is in position, small platinum coils are threaded through the catheter and into the aneurysm. These coils are soft and flexible, allowing them to adapt to the shape of the aneurysm. The role of the coils is to promote the formation of blood clots within the aneurysm. As the blood comes into contact with the coils, it begins to clot, gradually filling up the aneurysm over time. This process effectively isolates the aneurysm from the rest of the circulatory system, thus preventing it from rupturing. The coils are left in place and do not need to be removed.

After the coils are properly placed, the catheter is carefully withdrawn from the body. The patient is usually required to stay in the hospital for the night following the procedure to enable the medical team to monitor the recovery.

What is stent assisted coiling?

Stent-assisted coiling involves the insertion of a small, mesh-like tube called a stent in addition to tiny coils to treat the aneurysm.

Similar to coil embolisation, a tiny catheter is navigated through the blood vessels, starting from an access point typically in the wrist or groin, all the way up to the site of the aneurysm in the brain. A stent is then placed across the opening of the aneurysm, acting like a small scaffold that provides support to the blood vessel wall, which can be weakened due to the aneurysm.

Once the stent is in place, small coils are threaded through the catheter and placed into the aneurysm. The coils promote blood clotting, thereby filling the aneurysm and preventing it from rupturing. The stent helps to hold these coils in place and prevents them from slipping into the normal blood vessel. It’s particularly useful in treating wide-neck aneurysms, where the risk of coils slipping into the parent vessel (the blood vessel supplying the aneurysm) is higher.

After the procedure, you will likely need to take antiplatelet medications such as aspirin or clopidogrel, which help to prevent the formation of blood clots around the stent. This is a routine precaution and an important part of ensuring the success of the procedure. Antiplatelet medications are given in low doses and make the platelets in your blood less sticky, reducing the chance that a clot will form.

What is flow diversion?

Flow diversion is another minimally invasive endovascular treatment designed to manage brain aneurysms. The primary aim of this treatment is to divert blood flow away from the aneurysm and therefore prevent rupture.

A flow diverter, similar to a stent, is a small tubular mesh device that’s placed inside the parent artery, the blood vessel supplying the aneurysm. The flow diverter is designed to alter the blood flow dynamics in the artery, thereby diverting blood away from the aneurysm. They can be used with or without placement of coils in the aneurysm.

Over time, this decreased blood flow into the aneurysm encourages the formation of a blood clot within the aneurysm, which helps to seal it off from the rest of the blood vessel. As the aneurysm shrinks and heals, the artery resumes a more normal shape and function. This process can take several weeks to months.

Flow diversion is particularly effective for recurrent, large, wide-necked, or thrombosed aneurysms that can’t be adequately treated with other methods. It is also necessary to take antiplatelets after insertion of flow diverters.

What is an intrasaccular device?

Intrasaccuar devices such as the WEB (Woven EndoBridge) device may be used in the treatment of wide neck aneurysms which would otherwise require stents or flow diverters.

The WEB device, made of ultra-fine braided wires, is a flexible, self-expanding mesh that resembles a tiny basket. It is introduced into the aneurysm using a catheter navigated through the blood vessels from a small incision usually made in the wrist or groin. Once inside the aneurysm, the WEB device expands to fit the shape and size of the aneurysm, serving as a barrier that disrupts the blood flow within. This promotes clot formation within the aneurysm, sealing it off and isolating it from the rest of the circulation, thereby reducing or eliminating the risk of rupture.

A benefit of the WEB device is related to post-procedure medications. With stents or flow diverters, patients are typically required to take antiplatelet medications for a period of time to prevent blood clot formation around the treatment site. However, because of the way the WEB device works, patients usually do not need to take these medications for a prolonged period.

Is endovascular treatment durable?

Yes. Endovascular treatment is highly effective at providing lifelong protection from brain aneurysms. For this reason it is now the most common method to treat brain aneurysms worldwide and has been employed to save countless lives.

In preventing adverse consequences such as disability or death endovascular treatment is as effective as surgical clipping. It is the recommended treatment in ruptured aneurysms as studies have shown that endovascular treatment is safer.

However, like any treatment, there is no absolute guarantee that an aneurysm treated with endovascular therapy will never recur necessitating additional procedures. In a large study retreatment was carried out in 4.9% of patients [1]. Rebleeding was exceedingly rare, occuring in less than 1 in 200 patients. It’s worth noting that surgical clipping, much like endovascular treatment, isn’t exempt from the possibility of requiring further intervention. For this reason endovascularly treated aneurysms are regularly monitored with follow-up scans to ensure that the treatment remains effective. If a further treatment is required this can normally be performed safely in a planned elective setting also with an endovascular procedure.

Overall, endovascular therapy provides a highly effective and durable treatment. After embolisation of a brain aneurysm you would be more likely to die from another completely unrelated cause such as cancer of heart disease, than from recurrence of the aneurysm [3].

What are the risks of endovascular treatment?

Endovascular embolisation of aneurysms is normally performed successfully without complication, but all medical treatments carry the potential for risk.

Recovery is usually relatively rapid after endovascular treatment. Patients typically spend one night in hospital for monitoring and are discharged the day after. The site of arterial entry in the wrist or groin might be sore for a few days when it heals. Rarele there are minor side effects like oozing or bleeding from these sites. Applying pressure usually stops this. A small, typically temporary bruise may also form. Occasionally the patient might experience headaches that typically settle over days to weeks.

Serious but rare risks include a 5% chance of stroke from the procedure due to aneurysm rupture or blood vessel occlusion, causing potential limb weakness, speech or vision difficulty which could be temporary or permanent. A very rare 1% risk of a severe brain injury leading to death exists. There is a small chance of vessel damage in the groin or wrist from the catheter entry necessitating surgery.

Surgical treatment

Surgical clipping is an established but more invasive method of treatment that still has a role in managing certain cerebral aneurysms. The procedure involves making an opening in the skull (a procedure called a craniotomy) to locate the aneurysm. With the help of a microscope, the surgeon places the clip on the aneurysm’s neck, sealing it off from the rest of the blood vessel.

Recovery times vary but are typically longer than for endovascular treatment. Like all surgical procedures clipping carries some risks. Strokes occur in about 5% of cases which can manifest as weakness in the limbs, disturbances in speech, or visual problems. There is about a 1% chance of catastrophic brain injury resulting in death. The surgery might also affect the area of your brain near the aneurysm. This could lead to short-term effects due to swelling or bruising, or in rare cases, long-term effects. These effects would be specific to the location of each aneurysm and may also cause neurological stroke-like symptoms.

The procedure can lead to some physical discomfort in the days following the surgery. Swelling and bruising to the face are common, which might cause your eyes to close temporarily. Alongside this headaches are relatively common. The wound site can become infected. One unusual sensation some patients note is the feeling that the bone flap, the piece of bone removed during the surgery, seeming to move. This sensation, while strange, is not dangerous. The bone flap is secured with plates during the operation and will heal properly in time. The muscle used for chewing food might be impacted temporarily by the operation. As this muscle heals, you might find it challenging to open your mouth or chew, but these symptoms typically resolve within six months.

The period following the operation requires careful management of your activities. In the first few weeks after going home, it’s essential to maintain a routine, stay hydrated, eat well, and rest regularly. Enlist help for household chores if possible and consider some gentle exercise to gradually build up your strength. Most people require about 2-3 months off work for full recovery. Returning to work earlier won’t necessarily harm you, but it may prolong the recovery period due to increased tiredness.

However, in skilled hands, surgical clipping can provide a solution for many types of aneurysms, particularly those that may not be suitable for other treatments, like coil embolisation or flow diversion.

References

1. Rizvi A, Seyedsaadat SM, Alzuabi M, Murad MH, Kadirvel R, Brinjikji W, Kallmes DF. Long-Term Rupture Risk in Patients with Unruptured Intracranial Aneurysms Treated with Endovascular Therapy: A Systematic Review and Meta-Analysis. AJNR Am J Neuroradiol. 2020 Jun;41(6):1043-1048. doi: 10.3174/ajnr.A6568. Epub 2020 May 28. PMID: 32467181; PMCID: PMC7342755.