Description, Causes and Risk Factors:
Alternative Name: Spontaneous occlusion of the circle of Willis.
Moyamoya disease was first described by Suzuki in 1963. It is an idiopathic progressive occlusive cerebrovascular disorder of unknown etiology characterized by progressive narrowing or frank occlusion of distal internal carotid arteries (ICA) & proximal circle of Willis vessels with secondary collateralization. In addition to the enlarged lenticulostriate and thalamoperforator arteries, multiple leptomeningeal and transdural anastomoses develop between the cortical arteries and those of dura mater, scalp, and orbit. Moyamoya disease occurs primarily in Asians, but it can also occur in other populations. It is more common in females & shows bimodal age peaks: 6 years and beyond 35 years.
The idiopathic or primary form of moyamoya disease, which is sometimes familial has to be distinguished from the secondary form, referred to as Moyamoya syndrome, which can be associated with certain similar phenomenon and can be caused by occlusion of bilateral supraclinoid ICA by atherosclerosis, sickle cell disease, chronic basilar meningitis, neurofibromatosis, X-ray irradiation, homocystinuria, and Down syndrome.
In sickle cell disease, cerebrovascular complications occur in 1 to 17% of patients and are related to moyamoya syndrome, cerebral infarction and sinus thrombosis. In moyamoya syndrome related to sickle cell disease, the occlusion of internal carotid arteries is caused by at least one of the three following causes: vasa vasorum infarcts due to sickle cell emboli, endothelial damage, and chronic hypoxemia due to hyperviscosity. It has been stated that chronic occlusion of internal carotid arteries resulted in leptomeningeal vasculature hypertrophy, to supply brain cortex. This phenomenon appears on post-contrast T1- weighted images as a leptomeningeal enhancement, also known as the “ivy sign.”
Research also believes linkage was found between the Moyamoya disease type 1 and markers located at 3p26-p24.2, although the exact underlying cause remains unknown.
Children with the idiopathic form or Moyamoya disease typically present with cerebral ischemia versus hemorrhage in adults.
Prognosis depends on the age and stage at diagnosis, the rapidity and degree of collaterals developed. After a progressive course for many years, the disease frequently stabilizes with residual disability.
Generally, the clinical features are those associated with TIAs (transient ischemic attacks) more common with children and stroke (hemorrhagic - more typical in adults).
Other symptoms include headache, hemiparesis, seizures, disturbed consciousness, speech deficits (aphasia), sensory and cognitive impairments, involuntary movements and vision problems.
The disease is always confused with other cerebrovascular diseases. The diagnosis may often include a series of scans, which may include:
Computed tomography (CT) and magnetic resonance imaging (MRI) scans may provide initial indications of the disease. If the disease is suspected, cerebral angiography, a test that creates images of the blood flow through the brain, is conducted to establish the diagnosis. For this test, an x-ray is taken after a special dye is injected into the arteries. Magnetic resonance angiography (MRA), another imaging study that shows the blood vessels in the brain, also may be used.In a child with moyamoya disease, the angiogram will show blockage of the internal carotid artery, an abnormal network of blood vessels (the “puff of smoke”), and similar attributes on both sides of the brain.
In addition, SPECT (single photon emission computerized tomography) scans may be used to identify the regions of the brain that are not receiving sufficient oxygen.
Moyamoya disease is progressive, and some children may experience significant neurological impairment before treatment can be administered. In these cases, treatment addresses only the symptoms of the disease. There is no evidence that medications slow the progression of moyamoya disease. However, selected children suffering from recurrent or progressive loss of blood flow to certain parts of the brain may be candidates for surgery.
Many surgeries have been developed for the condition, but currently the most favored are the indirect procedures EDAS (encephaloduroarteriosynangiosis), EMS (encephalomyosynangiosis), and the direct procedure STA-MCA bypass. Direct superficial temporal artery (STA) to middle cerebral artery (MCA) bypass is considered the treatment of choice, although its efficacy, particularly for hemorrhagic disease, remains uncertain.
Rehabilitation is used for patients with neurological deficits, such as speech problems or paralysis.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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