What is Moyamoya Disease?

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In the video below, David Newell, M.D. talks about Moyamoya disease, who it affects, and how it’s treated. 

View full text/transcript for this video

Moyamoya is a rare cerebrovascular disease that reduces the flow of blood to the brain.

Moyamoya can result in brain hemorrhaging, transient ischemic attack (TIA, or "mini-stroke:) or a major stroke. It is also associated with brain aneurysms.

It was first described in Japan, where moyamoya means "puff of smoke." It was so named because it results in a tangle of fragile blood vessels that resembles a puff of smoke when viewed on an angiogram.

Moyamoya: Patient Experience
Moyamoya: a Progressive Disease
Who does Moyamoya Affect?
Diagnosing Moyamoya
Treating Moyamoya
Why Swedish?

Moyamoya: Patient Experience

Moyamoya: a Progressive Disease

Moyamoya causes a narrowing or blockage of the carotid arteries where they enter the brain at the base of the skull. The carotid arteries are the main arteries that supply blood and oxygen to the brain. This narrowing restricts blood flow – and therefore oxygen – to the brain.

It is a progressive disease, causing other blood vessels in the brain to continue to narrow over time.

The body tries to compensate and restore blood flow by creating a network of tiny blood vessels that branch off from the arteries. Unfortunately, the newly formed blood vessels are fragile, and ineffective in restoring blood flow. These fragile vessels can rupture and bleed.

The underlying cause of moyamoya is unknown, but it is thought to be linked to genetics and environmental triggers.

Who does Moyamoya Affect?

The greatest incidences of moyamoya are found in Asian countries – particularly Japan and Korea – but it is also found in the U.S. and around the world.

There are two ages where the disease tends to peak — one at about age 5, and the other at about age 40. Children with moyamoya are more likely to have TIAs or strokes. In adults, moyamoya more often leads to brain hemorrhaging.

Diagnosing Moyamoya

Severe headaches, seizures or stroke-like symptoms can be the first clinical signs of the disease.
A diagnosis of moyamoya is confirmed with a cerebral angiogram – a medical imaging study used to visualize the inside of blood vessels in the brain.

A number of other imaging tools are used to lead to this diagnosis, including:

  •  CT, CTA or MRI scans that show details of inner structures of the brain
  •  Doppler ultrasound, including transcranial Doppler that measures blood flow velocity
  • Brain blood flow studies using various tools, including SPECT (single photon emission computerized tomography) that show how blood flows to tissues

Although other conditions – including atherosclerosis (hardening of the arteries), meningitis, and brain tumors – can also cause a narrowing of major arteries, they are not associated with moyamoya.

Treating Moyamoya

While a number of medications have been tried in patients with moyamoya, surgery remains the most effective treatment.

Without surgery, most patients would experience mental decline and multiple strokes because of the progressive narrowing of the arteries. When it results in brain hemorrhaging, moyamoya can be fatal.

Two surgical options that have proven successful are indirect revascularization and direct revascularization. The goal of both procedures is to restore blood flow to the brain.


Direct revascularization

Direct revascularization involves suturing blood vessels in the scalp to blood vessels in the brain. Using microsurgery, neurosurgeons often suture the superficial temporal artery to the middle cerebral artery.

(The superficial temporal artery is along the side of the head, and the middle cerebral artery is one of the main arteries supplying blood to the forward part of the brain.) 

This procedure is often very effective in rapidly increasing blood flow.

Indirect revascularization

Indirect revascularization encourages healthy new blood vessels to growth in the brain. The procedure involves taking a small section of scalp tissue containing blood vessels, and sewing it to the firm layer of tissue that covers the brain.


Over time, new blood vessels develop. This procedure is used primarily on children, because their blood vessels are most often too small to connect them directly.


Surgical Outcomes

Revascularization surgery is done to reduce the risk of TIAs, stroke and brain hemorrhage. In most moyamoya patients, blood flow to the brain improves almost immediately.

Any surgery carries some risk, and potential complications from revascularization can include infection, bleeding and stroke. Fortunately, these complications are uncommon.


Why Swedish?

The specialists at the Swedish Cerebrovascular Center are highly skilled and experienced in treating patients with moyamoya.

Our expert team includes our neurosurgeon, neuro-anestheologist, neuro-interventional radiologists, stroke neurologist, as well as our clinical nurses and scheduling staff.

Everyone on the team collaborates and communicates with each other to ensure our patients receive the highest level of care.

Full text/transcript for What Is Moyamoya Disease? video

Moyamoya disease is a disease of the brain and blood vessels where the arteries become severely narrow as they enter the brain from the base of the skull.

The symptoms of moyamoya are most commonly transient ischemic events or transient events of numbness, weakness, and speech disturbance. They can occur eposodically and then progress even to a full blown stroke if the condition is not recognized and treated properly. The typical demographic is a young woman with an unexplained stroke that doesn't have a lot of risk factors for stroke.

Moyamoya was first described in Japan and it has been noted to be more common in Asian populations. The moyamoya refers to a puff of smoke. That's the Japanese word for puff of smoke, and when you get an angiogram or an injection of the blood vessels, these fine vessels that form in response to the larger disease vessels that start to block off appears as a puff of smoke or a small, fine nest of vessels that forms to try to reroute the blood around the blockage in the arteries.

One of the treatments for moyamoya disease is simple aspirin therapy because we want to thin the blood out to prevent it from clotting in these narrowed vessels.

The two surgical treatments are called direct and indirect bypass procedures. And we take a vessel called the superficial temporal artery, which is an artery in the scalp, and hook that up to some vessels on the surface of the brain. Now we can do a direct anastimosis or a direct connection, similar to a heart bypass procedure, where we sew the vessels together and provide a route for the bloodflow. If the blood vessels are too small or not amenable to that procedure we can do what's called an indirect procedure where we lay the vessel from the scalp on the surface of the brain and the vessels from the scalp eventually grow in and provide connections in to the brain vessels. That takes longer for that to occur, typically three to six months for that to occur in a major way. So the direct bypass is preferred if it can be done technically because it provides an immediate increase in blood flow to the brain.

In most patients the bypasses have a good long term effectiveness or longevity. When we look at the bypasses over time, if there's blood demand, those vessels often enlarge quite a bit to even reach the size of the original arteries that were blocked off. And we've studied a number of patients over time and repeated their imaging and found that the vessels in most patients do stay open and continue to provide blood flow around the diseased arteries.

There are small risks to the surgery just like any surgery, which include small risk of infection, fluid leakage, a very small risk of stroke or brain adema, but most patients do extremely well and the patency rate or the rate that the bypasses stay open is quite high. It's over ninety percent in these patients.

At Swedish Neuroscience Institute we have an active program to treat moyamoya patients. We have a large experience in treating them. We utilize special anesthetic techniques, including cooling the patient during the surgery to prevent any reduction in blood flow and there's a team that's done a lot of these bypasses and they're very, very good at it.