Approach Considerations
Misdiagnosis and delayed diagnosis of moyamoya disease are particular pitfalls in the treatment of patients with this disorder. Misdiagnosis can occur easily if the physician does not incorporate moyamoya disease into the differential diagnosis of any patient presenting with stroke. How high moyamoya disease is ranked in the differential depends on presence of atypical features such as young age and absence of obvious risk factors for stroke.
If moyamoya disease is not considered seriously, then appropriate diagnostic tests may not be performed and a delay in diagnosis could result. Because definitive treatment may be surgery, any delay could allow unnecessary progression of disease.
If an ischemic stroke progresses despite preventative treatment with antiplatelet agents or anticoagulants, then moyamoya disease should be considered as a possible etiology. This is especially true if results of a hypercoagulability profile are unremarkable.
Physicians practicing in the community who encounter atypical stroke presentations should not hesitate to seek consultation with a stroke specialist or even to transfer a patient to a facility equipped to care for complex cases.
Laboratory Studies
Several studies may be indicated in patients with moyamoya disease. In a patient with stroke of unclear etiology, a hypercoagulability profile may be helpful. Significant abnormality in any of the following is a risk factor for ischemic stroke:
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Protein C
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Protein S
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Antithrombin III
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Homocysteine
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Factor V Leiden
The erythrocyte sedimentation rate (ESR) can be obtained as part of the initial workup of possible vasculitis. However, a normal ESR does not rule out vasculitis.
Thyroid function and thyroid autoantibody levels have been shown to be elevated in a significant percentage of pediatric patients with moyamoya disease. [11] Therefore, monitoring these studies is indicated.
Angiography
Cerebral angiography is the criterion standard for the diagnosis of moyamoya disease. The following findings support the diagnosis:
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Stenosis or occlusion at the terminal portion of the internal carotid artery or the proximal portion of the anterior or middle cerebral arteries
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Abnormal vascular networks in the vicinity of the occlusive or stenotic areas
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Bilaterality of the described findings (although some patients may present with unilateral involvement and then progress)
Magnetic resonance angiography (MRA) or computed tomography angiography (CTA) can be performed. Any of the above findings on MRA or CTA may preclude the need for conventional angiography.
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Schematic representation of the circle of Willis, arteries of the brain, and brain stem.
