Conventional digital subtraction cerebral angiography of a 7-year-old girl who presented with left hemiparesis. (A) Anteroposterior image of right-sided circulation indicates stenosis at the terminal portion of the right supraclinoid internal carotid artery, proximal middle cerebral artery, and anterior cerebral artery, with a network of abnormal moyamoya collateral vessels (arrow). (B) Anteroposterior image of the left internal carotid artery circulation demonstrates stenosis of the proximal portion of the left anterior cerebral artery (arrow), with poor distal filling. The left internal carotid artery and middle cerebral artery are relatively unaffected.

A 15-year-old girl presented acutely with left unilateral monoparesis. (A) Axial T2-weighted magnetic resonance images indicate acute right middle cerebral artery territory infarct, with several small, focal areas of high signal within the frontal white matter of the centrum semiovale, representing small subcortical infarcts. (B) Magnetic resonance angiography demonstrates narrowing of the right internal carotid artery termination and poor visualization of the anterior cerebral arteries bilaterally (arrows). (C) Preoperative planning digital subtraction angiography confirms terminal stenosis of the right internal carotid artery (thin arrow) and, to a lesser extent, proximal stenosis of the right anterior cerebral artery (dotted arrow) and middle cerebral artery. An extensive network of moyamoya collateral vessels (thick arrow), not detected on magnetic resonance angiography, has formed between the internal and external carotid vessels.

A 6-year-old boy with idiopathic moyamoya disease presented after a left hemispheric infarct. Axial T2-weighted magnetic resonance images demonstrate established watershed infarction in the left frontal lobe (A), multiple basal moyamoya vessels (B; arrows), and poor visualization of the internal carotid artery terminations bilaterally (arrows) (C). (D) Magnetic resonance angiography reveals bilateral terminal internal carotid artery occlusion (arrows), bilateral middle cerebral artery stenosis, and bilateral proximal anterior cerebral artery occlusion. (E) Small moyamoya vessels are present (arrows). All images were obtained from a 3.0 T machine.

A 5-year-old girl with sickle cell disease presented with increasing episodes of transient ischemic attacks. (A) Transcranial Doppler imaging indicated abnormally high blood flow velocities in both the internal carotid arteries and middle cerebral arteries (right middle cerebral artery [RT MCA M1] demonstrated an average velocity of 196 cm/second). Subsequent magnetic resonance imaging/magnetic resonance angiography revealed numerous signal voids (black dots) in the region of the basal ganglia representing moyamoya vessels (B), significant stenoses at the distal right internal carotid artery, proximal right middle cerebral artery (arrow), and origin of the right anterior cerebral artery and narrowing of the left middle cerebral artery (C). No acute or established parenchymal infarcts were evident.

A 9-year-old girl with sickle cell disease and increasing blood flow velocities in the left internal carotid artery and middle cerebral artery on transcranial Doppler imaging during the preceding 4 months presented acutely with visual disturbance. (A) An acute left posterior cerebral artery territory infarct appeared bright on magnetic resonance diffusion-weighted imaging, reflecting restricted diffusion from cytotoxic edema. (B) Magnetic resonance angiography revealed extensive signs of moyamoya disease, with a high level of stenosis in the internal carotid artery terminations bilaterally, and numerous collateral vessels filling the distal middle cerebral artery branches. (C) Both posterior communicating arteries were fetal, which was thought to be the reason for the left posterior cerebral artery territory infarct. The left posterior communicating artery is attenuated because of the infarction.

A 3-year-old girl presented with signs of meningism. Initial computed tomography with contrast enhancement (A and B) indicated extensive low attenuation in the regions of the basal ganglia and internal capsules bilaterally, extending to the inferior frontal lobes and temporal lobes. Multiple, irregular, ring-enhancing lesions, consistent with tuberculomata, are present in the suprasellar region and extend along the course of both middle cerebral arteries. Moreover, a focal infarction of the right caudate nucleus and abnormal thickening and enhancement of the pituitary stalk are evident (the patient was diagnosed with diabetes insipidus). In addition, abnormal ependymal enhancement is evident, particularly of the right lateral ventricle, suggesting ventriculitis. (C) Subsequent magnetic resonance angiography revealed terminal stenosis of the left internal carotid artery and proximal stenosis of the left anterior cerebral artery and middle cerebral artery, together with moyamoya collateral vessels.

A 5-year-old girl without a remarkable medical history presented with repeated episodes of transient left-sided weakness after episodes of crying. (A) Magnetic resonance angiography demonstrates predominantly right-sided disease, with occlusion of the proximal right middle cerebral artery (small arrow) and established collaterals between distal middle cerebral artery branches and the right superficial temporal artery (large arrow). (B) Axial T1-weighted, gadolinium-enhanced image reveals right-sided leptomeningeal flow engorgement, i.e., the ivy-sign.Axial postgadolinium perfusion-weighted imaging mean transit time maps, before and after acetazolamide challenge (C and D, respectively), demonstrate abnormal perfusion of the right hemisphere. Dark areas equate with shorter mean transit times and increased perfusion (indicated as arrows in the normally perfused left hemisphere in C). (D) A normal increase in dark areas follows acetazolamide challenge in the left hemisphere, but with more reduced perfusion on the right (white areas, predominantly right frontal horn periventricular white matter, as indicated by arrow), consistent with the known middle cerebral artery territory vasculopathy.