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.
Moyamoya Disease Treatment
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 percent. Consequently, the gold-standard treatment for moyamoya disease is revascularization surgery, a procedure that increases blood flow to the affected region of the brain.
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.
The cause of moyamoya disease is unknown, although genetic and environmental factors are thought to be involved. Between six percent and 12 percent 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 gets moyamoya disease?
Moyamoya disease can affect people from 1 to 60 years old, although most cases appear in people near the ages of 5 to 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.
Between six percent and 12 percent 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.
How is moyamoya disease diagnosed?
At the Moyamoya Disease Program at Barrow Neurological Institute at Dignity Health St. Joseph’s Hospital and Medical Center, you are seen by a neurologist or neurosurgeon and also by a neuropsychologist. You may undergo magnetic resonance imaging (MRI) 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.