Aneurysm coils work by blocking the flow of blood into the aneurysm. This is also known as coil embolisation. This process treats a brain aneurysm by filling it with a coil to isolate an aneurysm from the normal circulation without blocking off any small arteries nearby or narrowing the main vessel. This reduces the risk of bleeding.

This process is performed from “within” the artery hence known as ‘endovascular’. It uses a steerable catheter which is inserted at the groin into the bloodstream and guided to the brain. Doctors recommend coiling to treat a cerebral aneurysm that is ruptured or at risk of rupturing. 

How is the procedure performed?

A neurosurgeon or neuroradiologist who specialises in endovascular surgery will perform the coiling procedure. 

The doctor will shave and cleanse the inner thigh and groin area of the patient. The procedure may be performed under general anaesthetic or under monitored sedation.

A flexible, long, and thin tube made of plastic, called the catheter passes through a needle into an artery in the groin. 

The surgeon will inject a dye, known as a contrast agent into the bloodstream via the catheter. This makes the blood vessels visible on the X-ray monitor (fluoroscopy). 

The catheter is then carefully guided into the affected brain artery and the coil is placed at the site of the aneurysm. X-rays are used to guide the catheter into the artery. 

These coils are very soft and thin, made up of soft platinum metal,  shaped like a spring. Their size may vary from being less than the width of human hair to about twice the width of human hair. 

Sometimes, coils may also be used with stents to prevent the coils from moving out of an aneurysm. 

Who is a good candidate for surgery?

Doctors believe that the choice of aneurysm treatment, be it observation, endovascular coiling, or surgical clipping – must be calculated against the risk of rupture. The overall general health of a patient is an important consideration. 

As coiling is less invasive, it is favoured among:

• older patients
  
• those with poor general health,
  
• those with any serious medical conditions
  
• those whose aneurysms are at specific locations and configurations
  

Coiling can be considered as an effective treatment in the following cases:

• Ruptured aneurysms that have burst open and are releasing blood into the space existing between the brain and the skull. This is called a subarachnoid hemorrhage (SAH). As there is a high risk of re-bleeding in ruptured aneurysms, urgent intervention is recommended . A common complication of SAH is the narrowing of an artery, also known as Vasospasm.
  

• Unruptured aneurysms that are asymptomatic. Often these are be identified during routine testing for another condition. The risk of aneurysm rupture is low at about 1% per year. However, the risk may vary depending on the size as well as the location of the aneurysm. It is notable that the risk of death and disability is high at 40% and 80%, respectively in case of a rupture.
  

Neurosurgeons recommend intervention with coiling when the risk of rupture outweighs the risks of intervention.

What are the risks associated with this procedure? 

• Allergic reaction: Risk of an allergic reaction to the dye used during X-rays for visualising the aneurysm.
  
• Bleeding: The doctor will recommend the patient to stop the use of anticoagulant medicines (such as aspirin, clopidogrel, warfarin).
  
• Vasospasm.
  
• Coil protrusion where the coils may poke through an aneurysm or blood vessel.
  
• Incomplete occlusion: when the coil may not completely fill the aneurysm. In this case blood can enter the residual neck, causing the aneurysm to recur.
  
• Hematoma: swelling caused due to collection of blood in the area in the groin, from where the catheter had been inserted.
  
• Stroke or a transient ischemic attack (mini-stroke) from a blood clot or a coil that has moved into the artery.
  
• Rupture of aneurysm: This can occur due to the puncture of an aneurysm from the catheter, a guidewire, or even the coils themselves. It happens in only about 5% of the ruptured aneurysms, especially those that already have a weakened wall. It is less common in unruptured aneurysms.
  

Recovery from surgery

Post-surgery, the patient will be taken to the recovery room or the ICU for observation. The patient will remain in a flatbed for 12 to 24 hours post-surgery. Nurses will monitor their vital signs, insertion site, nervous system, blood circulation and sensation in the affected leg.

The medical staff will provide pain medication to manage any pain or discomfort from the procedure or from lying flat on the bed for a long period.

Patients can resume their usual diet post-surgery unless their doctor advises otherwise.

Although patients can to go back home upon recovery from the surgery in 1 to 2 days, some patients may need to stay longer especially if they were treated for a ruptured aneurysm. This is to monitor for any complications that may develop such as vasospasm or hydrocephalus.

Post-surgery, patients may be advised to not do any strenuous activity. Your doctor will guide you when you can resume work and normal day-to-day activities, even including flying. 

Doctors will also advise follow-up schedules and any tests that need to be conducted periodically to assess the success of the surgery. Generally, a cerebral angiogram is scheduled after 1 month of the surgery. This is a test to ensure that the coiling is working fine. The doctors will also assess and advise the need for any other cerebral angiograms or imaging tests such as an MRI or MRA. 

Coiling vs clipping

Procedure: Coiling is a minimally invasive procedure and patients can be discharged from the hospital in 1 to 2 days. Patients who undergo aneurysm clipping may have to stay in the hospital for a longer time.

The choice of procedure is based on multiple factors including patient factors and aneurysm factors .

Safety: The difference in safety between coiling vs. clipping is very small for patients <40 years of age. Doctors may select treatment considering better and long-term protection from bleeding for such patients. Therefore, clipped aneurysms may have an advantage for improved life expectancy for this group of patients. 

Frequently asked questions

How long does a brain aneurysm coiling last?

Chances of an aneurysm to re-bleed after coiling are higher immediately after the procedure. The chance is 1.9% within 30 days of surgery. However, between 30 days to 1 year, the chances of re-bleeding are only 0.6%. 

Can all aneurysms be treated by coiling?

Not all aneurysms can be treated by coiling and some might require surgical clipping. Ruptured aneurysms require immediate surgical attention as a delay in treatment can lead to hemorrhage. In some other types, such as wide-necked aneurysms, coil placing might not be feasible.  

Can a coiled aneurysm bleed again?

The procedure is successful in around 80-85% of the cases. In the remaining 15-20% of cases, there are chances of reoccurrence.

When can you return to driving after coiling?

In an unruptured aneurysm treated by coiling there are no specific restrictions. It is advisable to avoid driving or any other strenuous activity for at least a month after the procedure. 

Do you need to be on blood thinning medications for long time after aneurysm coiling?

The doctor may or may not prescribe blood thinners for few days post the surgery. This depends on the condition of the patient and other factors such as use of stent with a coil or protrusion of a coil. Rarely long term blood thinners are required.

Can you have an MRI or be in magnetic fields after having aneurysm coiling?

Yes, the coil generally does not interact with the magnetic field. It is safe to go for an MRI after the procedure.