An extracranial-intracranial bypass involves redirecting blood flow from outside to inside your brain past a complete blockage. Experts question its effectiveness, and the procedure is rarely performed.

In an extracranial-intracranial bypass (EC-IC), surgeons create a new passage between a branch of your external carotid artery to a branch of your internal carotid artery. They may use a graft from another part of your body or a donor to connect these blood vessels.

At this point, it’s considered an experimental procedure and only performed in a few centers worldwide. Some experts debate whether the procedure should still be performed, arguing that recent research hasn’t shown any significant benefit. For example, a 2020 trial was cut short, with the authors concluding the surgery had no benefit.

Read on to learn more about EC-IC bypasses, including what conditions they’re used to treat and what happens during the procedure.

An EC-IC bypass is used to improve blood flow to your brain if you have a complete blockage of one of your two internal carotid arteries. It’s performed to reduce your future risk of a stroke.

You have one internal carotid artery on each side of your neck. Along with your vertebral arteries, they’re one of the two pairs of arteries that supply blood to your brain.

Some of the specific reasons doctors may recommend an EC-IC bypass include:

  • complete blockage of an internal carotid artery due to plaque buildup
  • bypassing an internal carotid aneurysm
  • moyamoya disease, a progressive disease that leads to the narrowing of the carotid artery
  • blood vessel damage from tumor removal or removal or an arteriovenous malformation

Every surgery comes with some risks, including EC-IC bypass. Potential complications include:

In a 2023 study researchers reported no complications causing permanent neurological impairment among 86 people receiving nonemergency EC-IC bypass. This small case review was done at a highly specialized center.

In the same 2023 study, researchers found that nonemergency EC-IC bypass might be a feasible treatment for reducing large narrowing of the internal carotid artery in people with symptoms due to plaque buildup.

In a 2019 study, researchers found that, in the 30 days after surgery, EC-IC reduced the risk of stroke, brain bleeding, or death by five times in people with reduced brain blood flow.

In contrast, in another 2023 study, researchers found that EC-IC didn’t reduce the risk of stroke or death within 30 days among 309 people treated for blockage of their internal carotid artery or middle carotid artery.

The 30-day risk of stroke or death was 6.2% in people who received surgery and 1.8% in people who didn’t receive surgery. The risk of ischemic stroke on the same side between 30 days and 2 years was 2% in people who received surgery and 10.3% in those who didn’t.

The viability of EC-IC bypass has been debated in the literature for decades, and current opinion is that more research is needed.

Here’s a general idea of what to expect before and after an EC-IC bypass.

Before EC-IC bypass

You’ll meet with your surgical team before your surgery where they’ll explain the procedure and give you a chance to ask questions. You’ll also receive tests to measure your brain and overall health, such as:

During EC-IC bypass

Here’s a general idea of what you can expect:

  1. You’ll receive general anesthesia through an IV that’s usually connected to your hand or arm.
  2. Your surgeon will make an incision near your ear to access a branch of your external carotid artery. They will disconnect this branch and may also remove a blood vessel from another part of your body to make the connection.
  3. Your surgeon will perform a craniotomy, which means removing part of your skull to expose your brain. They’ll make an incision in your scalp and remove a piece of bone. They’ll then cut through the protective layers of tissues surrounding your brain.
  4. Your surgeon will connect the branch of your external carotid artery past the blockage in your internal carotid artery.
  5. Your artery will be connected to a blood vessel in your brain, and the piece of bone that was removed will be connected again. You’ll receive stitches in your skin, and your wounds will be covered with bandages

How long does EC-IC bypass surgery take?

An EC-IC is an extensive procedure that requires a craniotomy. A craniotomy usually takes around 2.5 hours and can take up to 5.5 hours.

After EC-IC bypass

You’ll wake up from your procedure in the recovery area. You’ll likely be connected to an IV and machines to monitor your vitals. You may also have a catheter attached to your bladder and have a tube connected to your wound to help it drain.

You can expect to stay in a hospital for 5 to 10 days after a craniotomy.

Your doctor will give you specific instructions on preparing for your surgery. You won’t be able to eat at least 6 hours before your procedure and won’t be able to drink for up to 2 hours before. Follow the specific instructions given to you by your surgeon.

If you smoke, your doctor will likely encourage you to stop smoking before your surgery to reduce your risk of complications.

Recovery from a craniotomy can take 6 to 12 weeks. You won’t be able to drive during this time and you won’t be able to fly until your surgeon says it’s OK to do so. It’s recommended to avoid contact sports after any brain operation.

Narrowing of your carotid artery may sometimes be treated with medications alone. Other surgical treatments include:

The cost of your procedure depends on factors like where you live and the extent of your procedure. The non-profit FAIR Health estimates that 80% of procedures to connect arteries of the head in Denver, Colorado, cost less than $16,919 without insurance. The cost of anesthesia could be another $8,407.

Your insurance may or may not cover the cost. Medicare does not cover the cost due to a lack of research demonstrating its effectiveness.

EC-IC is a type of surgery used to improve blood flow to your brain. It may be recommended if you have complete blockage of your internal carotid artery that supplies your brain. It may also be used to treat a blockage due to moyamoya disease.

EC-IC is a major surgery and your doctor can help explain the potential benefits and risks. They can also recommend if any surgical procedures may be a better option.