Case Report

Thrombosed Large Distal Posterior Inferior Cerebellar Artery Aneurysm Mimicking an Infratentorial Ependymoma

Figure 1

Noncontrast enhanced CT brain showing a hyperdense midline lesion of the posterior fossa ((a), axial). T1W MRI sequences depict a hypointense lesion, apparently intra-axial, arising from the floor of the fourth ventricle compressing against the superior medulla ((b), axial). The lesion demonstrates gadolinium contrast enhancement and is abutting the PICA, white arrowhead ((c), T1W contrast, axial; (d), sagittal). T2W MRI revealing significant perilesional medullary edema, white arrows ((e), sagittal). SWI sequence showing blooming artifacts within the lesion and its proximity to the PICA, black arrowheads ((f), axial). Three-dimensional reconstructed contrast-enhanced MRA showing no detectable vascular lesion (g). The “target” sign is observed only in the coronal contrast T1W images ((h), (i)).
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(a)
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(b)
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(c)
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(d)
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(e)
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(f)
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(g)
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(i)