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A highly vascular tumor.
An intra axial posterior fossa mass with cyst and an enhancing mural nodule is a diagnostic clue.
Currently classified as meningeal tumor of uncertain histogenesis (WHO, 2000)
Locaion:
90% posterior fossa (m/c) in that 80% cerebellar hemispheres, 15% Vermis, 5% in other places fourth ventricle, medulla.
10% Supratentorium.
In ~ 60% of cases mass present as cyst + mural nodule and in ~ 40% of cases only as a solid nodule.
Imaging findings:
Cyst is clear, density on CT and signal intensity on MRI same as that of Csf, non enhancing thin imperceptible wall.
Mural nodule on CT may be iso to hyper dense, intense and homogenous enhancement. On MRI hypo to iso intense on T1, hyperintense on T2 and FLAIR. May see flow voids within the nodule with adjacent vascular feeders on T2w images, intense and homogenous enhancement on T1 images implies to its highly vascular nature. May show low signal intensity hemosiderin staining on GRE if associated to with any bleed.
Presentation is usually with headache, dysequilibrium, dizziness may be due to its mass effect and hydrocephalus.
Age : for sporadic: 40-60 yr and for familial : can occur at younger age. Slight male predominance.
Closest DD is Pilocytic Astrocytoma; mural nodule show mild to moderate enhancement not this intense, not characterized by flow voids and feeders. Seen in relatively younger age group.
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