What is moyamoya disease?
Moyamoya disease is a condition of progressive blockage of your internal carotid arteries. These vessels make up two of the four arteries that bring blood to your brain. When they become blocked, as in moyamoya disease, you could potentially suffer a stroke or cerebral hemorrhage.
What causes moyamoya disease?
The cause of moyamoya disease is unknown, although genetic and environmental factors are thought to be involved. Between 6-12% of patients with moyamoya disease have a family history of the condition. Abnormalities on chromosomes 3, 6, 8, and 17 have been linked to familial (inherited) moyamoya disease.
Moreover, a specific abnormality in a gene that codes for a smooth muscle protein called alpha actin (ACTA2) has been found in patients with familial (inherited) and nonfamilial (uninherited) forms of moyamoya disease. This ACTA2 abnormality is called a susceptibility gene for moyamoya disease and is also linked to early onset coronary artery disease.
Who can get moyamoya disease?
Moyamoya disease can affect people from 1 to 60 years old, although most cases appear in people near the ages of 5 or 35 years old. Women have a higher incidence of moyamoya disease than men. Individuals of Japanese and Korean ancestry have a higher incidence of moyamoya disease compared to other ethnic groups.
In the United States, the approximate incidence of moyamoya disease is 0.09 new patients per 100,000 people per year while the current prevalence is 0.9 cases of moyamoya disease per 100,000 people.
What are the risk factors for moyamoya disease?
Although the cause of moyamoya disease is unknown, a number of conditions are associated with moyamoya disease:
- sickle cell anemia
- cranial radiation
- Down syndrome
- congenital cardiac abnormalities
- renal artery stenosis
- congenital dwarfism
- neurofibromatosis type 1
When a condition like those listed above is associated with moyamoya disease, the disease is called moyamoya syndrome.
Can moyamoya disease be prevented?
There is no preventative treatment for moyamoya disease.
Is moyamoya disease hereditary?
Between 6 and 12% of moyamoya disease cases are considered familial, meaning that a first-degree relative of yours (i.e., your parents, your siblings, or your children) also will have the condition.
What medical therapies are used to treat moyamoya disease?
Medical management of moyamoya disease includes the following:
- maintenance of hydration
- use of antiplatelet agents like aspirin or Plavix (clopidogrel bisulfate)
- moderate control of hypertension
It is important to use caution when treating moyamoya-induced hypertension, because low blood pressure can lead to a stroke if you have moyamoya disease. Despite medical management, the incidence of subsequent stroke in all patients with moyamoya disease ranges from 60 to 80%. Consequently, the gold-standard treatment for moyamoya disease is revascularization surgery, a procedure that increases blood flow to the affected region of the brain.
How is revascularization surgery performed to treat moyamoya disease?
Revascularization procedures can include direct bypasses and indirect bypasses:
- In a direct bypass, surgical connections (anastomoses) are made between branches of your external and internal carotid arteries.
- In an indirect bypass, tissues such as arteries, muscle, galea (a tough, fibrous tissue underneath your scalp), or dura (the covering of your brain) are placed on the surface of your brain. The area of your brain suffering from insufficient blood flow (ischemia) naturally causes blood vessels to reconnect between the transplanted tissues and ischemic arteries on the surface of your brain. This process restores blood flow to the affected area.
What are the advantages of direct bypass surgery for moyamoya disease?
Your cerebral blood flow improves immediately after direct bypass surgery. Some studies also suggest the risk of complications is lower than with indirect revascularization.
What are the advantages of indirect bypass surgery for moyamoya disease?
Indirect bypass is not as technical of a procedure as direct bypass. Indirect bypass surgery is useful when the arteries on your brain are too small for anastomoses.
Is research being conducted on moyamoya disease?
Research is being conducted on the cause of and ideal treatment for moyamoya disease.
What tests are used to diagnose moyamoya disease?
Moyamoya disease is usually diagnosed with cerebral angiography. In this procedure dye is injected into the arteries in your brain, and images are taken to show the unique anatomy of the arteries that supply blood to your brain.
Magnetic resonance (MR) angiography and computed tomographic (CT) angiography can also be used. Magnetic resonance imaging is used to look for evidence of stroke or brain ischemia. A study of your cerebral blood flow such as CT perfusion or MR perfusion can help your surgeon locate regions of inadequate blood flow to your brain.
A neurologist or neurosurgeon will examine you to see if you have any neurological problems. In many cases, more formal neurocognitive testing is administered and analyzed by a neuropsychologist.
Do moyamoya disease patients ever need rehabilitation?
Stroke is the most significant problem caused by moyamoya disease. Medical and surgical management cannot prevent stroke in all cases of moyamoya disease. If you have moyamoya disease and you experience a stroke, you may need some form of rehabilitation.
How is moyamoya disease diagnosed at Barrow?
At the Barrow Moyamoya Disease Clinic, you are seen by a neurologist or neurosurgeon and also by a neuropsychologist. You may undergo MR imaging of your brain and cerebral angiography if you do not bring these studies from your referring physician. In most cases, a CT perfusion scan is also done to help assess the adequacy of blood flow to your brain.
How is moyamoya disease treated at Barrow?
Your neurosurgeon will determine whether you need surgical procedure for cerebral revascularization or medical management and close follow up.
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