UW Medicine Moyamoya Center at Harborview Medical Center

Table of Contents:

• What is Moyamoya Disease?
  
• What are the Symptoms?
  
• What is Moyamoya Syndrome?
  
• Treatment for Moyamoya Disease
  
• Case Examples
  
• Prognosis
  
• Contact Us

What is Moyamoya Disease?

Moyamoya disease (MMD) is a rare disease affecting the blood vessels to the brain, generally on both sides. It was first described in Japan in the 1960s and has since been found in individuals in the United States, Europe, Australia, and Africa.

The disease is characterized by the progressive narrowing and occlusion of the intracranial internal carotid arteries and their major branches due to progressive growth of the intima (the inner lining of arteries). In order to compensate for the narrowed/occluded middle cerebral and anterior cerebral arteries, the small branches of the vessels dilate and establish further connections inside the brain (called collateral circulation).

The brain also develops other collateral vessels through the pial circulation. As the disease advances, the dilated arteries in the base of the brain may develop small aneurysms, which can lead to rupture and brain hemorrhage. In a more advanced stage, even the collateral vessels become occluded. Ischemia (loss of blood flow at the microvascular level) occurs when the collateral circulation is unable to compensate for the metabolic demands of the brain. This is when patients develop symptoms of transient ischemic attacks (mini-strokes) or brain infarction (permanent brain stroke). In advanced stages of the disease, as the collateral vessels shut down, very severe brain ischemia and severe strokes occur. Moyamoya (Japanese for "puff of smoke") refers to the angiographic appearance of these abnormal vascular collateral networks. The steno-occlusive areas are usually bilateral, but unilateral involvement does not exclude the diagnosis.

Figure 1: This diagram at left depicts the lateral, or side-on view of the brain circulation on a cerebral angiogram in a patient with moyamoya disease.

The red arrow points to the occluded or blocked top of the internal carotid artery at the base of the brain.

As a result, a rich network of smaller "lenticulostriate" vessels has proliferated (blue arrow heads) to bypass the blockage. This gives the classic "puff of smoke" appearance (red circle). From the pial surface of the brain and the dura, more "collateral" vessel networks (green arrows) make their way across and into the brain to give the brain extra blood supply owing to the major blockage(s) deep within.

Moyamoya disease is more common in Asian populations, but can affect anyone. A recent study indicated that the prevalence of MMD in California and Washington was 0.086 cases per 100,000 population. It can occur at any time, but is most commonly diagnosed in childhood between age 5 - 15 and during adulthood between age 30 – 40, and slightly more common in females.

What are the symptoms?

In children, the symptoms of moyamoya disease are often:

1. Stroke (paralysis of different parts of the body, speech, memory loss or other areas of the brain)
2. Recurrent transient ischemic attacks (TIA, commonly referred to as “mini-strokes”, transient stroke like symptoms lasting a few minutes to a few hours)
3. Seizures

Adults most often experience a brain hemorrhage due to rupture of the dilated basal vessels. Less frequently, they present with ischemic symptoms due to decreased blood supply to the brain. About 50-60% of affected individuals experience speech deficits, sensory and cognitive impairments, involuntary movements, and vision problems from recurrent strokes.

Ischemic stroke, brain hemorrhage, seizures and death are the major complications of moyamoya disease. In persons with moyamoya disease, mortality rates (usually from brain hemorrhage) are approximately 10% in adults and 4.3% in children.

Causation of Moyamoya Disease

The exact etiology of MMD is unknown. Some genetic predisposition is apparent because it is familial 10% of the time. The disease may be hereditary and multifactorial. A recent Japanese study demonstrated that familial MMD is autosomal dominant with reduced penetrance.

What is Moyamoya Syndrome?

Moyamoya syndrome refers to cases in which artery changes occur as a consequence or result of another underlying disorder. In secondary moyamoya syndrome, when it is not a result of a genetic cause, it is important for the physician to determine the underlying root cause. Many disease states associated with this disease are:

• Immunological - Graves disease/thyrotoxicosis
• Infections - Leptospirosis and tuberculosis
• Hematologic disorders - Aplastic anemia, Fanconi anemia, sickle cell anemia, and lupus anticoagulant
• Congenital syndromes - Apert syndrome, Down syndrome, Marfan syndrome, tuberous sclerosis, Turner syndrome, von Recklinghausen disease, and Hirschsprung disease
• Vascular diseases - Atherosclerotic disease, coarctation of the aorta and fibromuscular dysplasia, cranial trauma, radiation injury, parasellar tumors, and hypertension

Diagnosis

Based on a patient’s symptoms and history, the physician may order one or all of these tests before making a decision about treatment:

1. Computed tomographic (CT) scans are used to diagnose brain hemorrhage from moyamoya disease. Magnetic resonance imaging (MRI) studies also identify areas of brain affected by stroke or hemorrhage and visualize the intracranial changes in moyamoya patients, and MR angiography can show the narrowing of vessels of the circle of Willis, and collateral circulation.
   
   
2. Cerebral angiography, by transarterial techniques using digital subtraction (DSA) is required for diagnosis. Contrast dye is injected into arteries to outline the anatomy of the arteries of the brain and scalp. This test assesses the severity of the disease and its results guide treatment options, which are determined by how severe the disease is and also reveal potential other arteries (scalp or neck) which can be used to bring new vessels to the brain.
   

   Figure 2: Lateral view in an angiogram showing MCA occlusion with prominent cortical collaterals consistent with Moya Moya disease

   
   The following findings support the diagnosis:
   • Stenosis or occlusion at the terminal portion of the internal carotid artery or the proximal portion of the anterior or middle cerebral arteries;
   • Abnormal vascular networks in the vicinity of the occlusive or stenotic areas;
   • Bilaterality of the described findings (although some patients may present with unilateral involvement and then progress).
   
   
3. Single Photon Emission Computed Tomography (SPECT) scan with and without Diamox challenge helps to characterize the amount of brain ischemia or circulation impairment and "cerebrovascular reserve."

Figure 3: The initial SPECT scan (above) indicates baseline blood reaching the brain and identifies areas of low perfusion. Following Diamox administration, a second scan is done to demonstrate impaired reserve or an actual "steal" phenomenon suggesting these brain regions are at high risk for subsequent stroke.

Treatment for Moyamoya Disease

Medical treatment with anti-platelet agents, anticoagulants, calcium channel blockers, or other drugs is mainly empirical with unproven benefits. Indications for treatment are in patients who present with ischemic symptoms, or asymptomatic patients who have an impaired cerebrovascular reserve. No immediate treatment may be recommended for patients who are asymptomatic and who are well compensated. For patients who present with brain hemorrhage, the benefits of surgery to prevent future hemorrhages are improved. However, based on our experience, (a lower level of evidence) surgical treatment is recommended.

Patients with moyamoya disease who present for treatment while symptoms are still evolving have a better prognosis than those who present with static symptoms (which probably indicate a completed stroke). The goal of offering surgery to patients with moyamoya disease is to prevent neurologic deterioration from strokes.

Various surgical procedures have been used and they can be divided into two groups depending on whether they involve direct or indirect anastomosis between the blood vessels. In some patients, if micro aneurysms are identified, endovascular occlusion of the vessel can be performed, particularly in association with bypass surgery.

Indirect procedures are generally preferred for children under the age of 10 and bypass procedures are generally performed in older children and adults. In the latter groups, the two types of procedures (indirect and direct) may also be combined.

Indirect Surgery

Children usually respond better to revascularization surgery than adults, and the majority of individuals have no further strokes or related problems after surgery. STA-MCA anastomosis is very difficult in children younger than 10 years because of the small diameter of the STA. Either the EDAS or the EDAMS procedure may be performed.

EDAS (encephalo-duro-arterio-synangiosis)/Pial synangiosis

In encephalo-duroarterio-synangiosis, first described by Matsushima et al., the superficial temporal artery is first dissected out as for an STA-MCA bypass, but is left in continuity. The dura is then opened in a linear fashion, and the artery is placed over the exposed cortex. Initial reports indicated that the vessel could be placed over the arachnoid, but further studies show that improved collateral flow can be obtained by opening the arachnoid and allowing the STA to contact the pia. The soft tissue cuff of the STA then is sewn to the edge of the dura with the expectation that it will eventually grow into the brain and therefore provide more blood flow.

This procedure does not involve temporary occlusion of an MCA branch and is technically easier to perform. In addition, EDAS can be used in cases where there is no suitable donor or recipient vessel, and it can also be used in conjunction with a STA-MCA bypass. This procedure sometimes has failed because of poor revascularization. In cases of EDAS failure, EDAMS can be considered.

Figure 4: Steps demonstrating the technique of pial synangiosis

EDAMS (encephalo-dural arterio-myo-synangiosis) This is another indirect bypass operation that combines EDAS with EMS to allow for collateral formation from both the STA and deep temporal arteries. In addition, along the margins of the dural opening, the dura is cut into leaf-like flaps which are then folded back under the dural margin into the epiarachnoid space so that the outer dural surface contacts the brain surface. This results in the promotion of collateral formation from the MMA as well. The temporalis muscle is then sutured down and used to cover the dural opening. As in the EDAS, 6-8 weeks are required after EDAMS for a new blood supply to develop from the transposed muscle.

Case Examples:

Case Report #1:
Pediatric Moyamoya Disease with Chronic Ischemia (Indirect Revascularization)

A 9-year-old girl of Asian descent presented with a history of decreased blood flow to the brain for 4 years and was treated with aspirin and calcium channel blockers. Her MRI scan was normal 4 years prior to presentation. She developed mini-stroke/TIA and evidence of strokes on her MRI scan. Angiograms showed bilateral internal carotid occlusion and a moyamoya pattern of collateral vessels. She underwent bilateral staged pial synangiosis with an interval of 6 weeks between each side. An angiogram at 1 year showed filling of cortical vessels from the external circulation bilaterally. At the 2-year follow-up, she had no symptoms of stroke and was normal.

Figure 5: A. preoperative magnetic resonance imaging (MRI) scan shows strokes. B. and C. angiograms showing bilateral MCA occlusion and collateral vessels from the ECA.

Figure 6: Intraoperative photographs showing approximation of the STA with pial/cortical surface (A) and 10–0 nylon stitches through the pedicle of STA and the pial/cortical surface

Figure 7: Postoperative angiogram showing bilateral filling of cortical vessels from the STA through the pial synangiosis.

Direct bypass graft (Superficial temporal to middle cerebral artery bypass)

This procedure benefits patients by providing an immediate improvement in blood supply to the brain by redirecting blood from the scalp into the brain. It is also known as an extracranial-to-intracranial bypass graft (EC-IC bypass). By performing STA-MCA bypass, a blood vessel from the scalp is directly joined to a vessel in the brain to improve the blood flow over a period of several months. If the STA is not suitable, radial artery or a saphaneous vein graft can also be used.

Figure 8: This diagram shows: A. terminal stitches are placed at the heel and the diametrically opposite ends. B. the opposite side is anastomosed with interrupted sutures.

Figure 9: This figure illustrates the use of the parietal branch of the middle meningeal artery for the superficial temporal artery - middle cerebral artery anastomosis. The heavy dotted line indicates the line of skin incision. Also show is hte site of craniotomy.	Figure 10: The terminal 1 cm of the superficial temporal artery is denuded of its adventitial covering.

Double STA-MCA bypass: In cases where higher flow is anticipated, a double bypass may also be created using both branches of the STA, one into the frontoparietal branch and another into a temporal branch to the distal sylvian branches of the MCA.

Radial artery graft: In some adult patients wherein the STA is very tiny, a radial artery graft procedure may be performed. This is also done to ECA to MCA or VA to MCA particularly useful in patients with moyamoya syndrome.

Case Report #2:
Adult Moyamoya Disease with Intraventricular Hemorrhage (Direct Revascularization)

A 23-year-old woman with an intraventricular hemorrhage attributable to moyamoya disease had right-sided paralysis and speech difficulty. She had a significant amount of clot in the brain and had a drainage procedure. A SPECT scan showed bilateral ischemia. A left-sided STA-MCA bypass was performed with a shunt for hydrocephalus. She had a right-sided STA-MCA bypass 5 months after the first surgery. After rehabilitation, she had recovered completely and was independent for activities of daily living. Angiography at 6 months showed considerable increase in the blood supply to the brain.

Figure 11: Preoperative angiograms showing bilateral ICA occlusion and collateral vessels from the vertebral system.

Figure 12: Postoperative angiograms showing bilateral STA-MCA bypass.

Case Report #3:
Moyamoya Syndrome Due to Radiation-Induced Bilateral Carotid Occlusion

A 60-year-old man had undergone radiation therapy after excision of tongue cancer 12 years earlier. He presented with multiple episodes of dizziness, passing out, and speech difficulty as well as left-sided visual blurring. Preoperative angiography showed left-sided ICA occlusion and right common artery and ICA occlusion with flow coming from the vertebral circulation as well as from the left-sided ECA circulation. Both transcranial Doppler and SPECT studies showed exhaustion of cerebrovascular reserve, particularly in the left hemisphere. He underwent a left-sided STA-MCA bypass. After 5 months, the SPECT scan showed ischemia on the right side. Because of this, a right-sided RAG bypass was performed from the VA to the MCA. The patient had no neurological problems, and both the grafts were patent 5 months after the last surgery.

Figure 13: Preoperative angiograms showing bilateral occlusion of the internal carotid artery (ICA) and MCA filling from the BA through the PComA and a good sized STA for the bypass.

Figure 14: Postoperative angiogram showing left side STA-MCA bypass filling the frontal MCA branches.

Figure 15: Postoperative angiograms showing vertebral artery (VA)-to-MCA radial artery bypass.

Video #1:

Video #2:

Prognosis

Without surgery, the majority of individuals with moyamoya disease will experience mental decline and multiple strokes because of the progressive narrowing of arteries, and can be fatal as the result of intracerebral hemorrhage.

Surgical treatment of moyamoya disease using various surgical techniques has been shown to be safe and effective in reducing ischemic events, in both adults and children, and, although the evidence is less conclusive, some studies suggest benefit for reducing hemorrhagic events. Post-revascularization angiography and MRI studies often reveal a reduction in moyamoya vessels that closely parallels improvement in symptoms.

We evaluate and treat many patients with Moyamoya Syndrome and Moyamoya Disease at the UW Medicine Moyamoya Center at Harborview Medical Center in Seattle, Washington.

How to contact us

To contact a member of the University of Washington Moyamoya Center to set up an appointment for consultation;

please call 206-744-9314 or
email moyamoya@u.washington.edu

Patient Care Introduction | Aneurysms | Brain Mapping | Case Studies | Chiari Malformation
Congenital Abnormalities | Epilepsy | Movement Disorders | Moyamoya Disease | Pain and Spasticity
Pediatrics | Peripheral Nerves | Radiosurgery and Radiotherapy | Spine
Stroke and Vascular Lesions | Trauma | Tumors

MAIN MENU