PMC8326142_01
Imaging performed in April 2017. (a) Preoperative T1 contrast enhancing MRI demonstrating a well-circumscribed lesion within the fourth ventricle. (b) Preoperative T2 MRI demonstrating no significant surrounding edema or infiltration of the normal brain parenchyma. (c) Preoperative DWI demonstrating no diffusion restriction. (d) Postoperative T1 contrast enhancing MRI demonstrating no obvious residual tumor.
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F1
After fundoscopic examination demonstrated Grade 5 papilledema, contrast-enhanced brain magnetic resonance imaging (MRI) was performed revealing a 4.8 x 4.4 x 4.1-cm mass centered in the fourth ventricle resulting in obstructive hydrocephalus [Figure 1].
(a) Low-power view demonstrating typical oval nuclei, low mitotic activity, and Rosenthal fibers. (b) High-power view demonstrating eosinophilic granular bodies.
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F2
The final pathology demonstrated presence of eosinophilic granular bodies and Rosenthal fibers with immunohistochemistry showing focal Olig-2 staining as well as GFAP and vimentin positivity confirming that the tumor was a World Health Organization Grade 1 pilocytic astrocytoma [Figure 2].
Imaging performed in March 2018. (a) T1 contrast-enhanced MRI demonstrating tumor recurrence within the frontal horns of the lateral ventricle. (b) T1 MRI demonstrating recurrent tumor within the third ventricle. (c) T1 MRI demonstrating leptomeningeal enhancement in the left cerebellopontine angle and temporal horns.
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F3
Repeat MRI demonstrated widespread tumor recurrence throughout the entire ventricular system and the subarachnoid spaces of the left cerebellopontine angle (CPA) suggesting leptomeningeal spread [Figure 3].