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case_images: Initial MRI imaging demonstrating mass and associated hydrocephalus. Sagittal (A) and axial (B) post contrast images demonstrating fourth ventricular mass with associated hydrocephalus.
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case_images: MRI brain revealed a heterogeneously enhancing mass in the fourth ventricle with obstructive hydrocephalus ( Figures 1 ,  2A ).
case_images: Serial MRI imaging demonstrating tumor changes over time. Axial high-resolution images on top panel, axial T1 post contrast images in middle panel and sagittal T1 post contrast images in bottom panel [(B) and (C) bottom are sagittal FLAIR images]. (A) Mass noted within the fourth ventricle resulting in supratentorial hydrocephalus and trans ependymal edema. (B) Post-operative MRI demonstrating residual tumor in the midbrain (arrow) and pons as well as roof of fourth ventricle (1 week post initial MRI). (C) Local tumor progression with enlargement of nodular component of dorsal midbrain mass and increased enhancement (64 months from initial diagnosis). (D) Completion of vinblastine chemotherapy, tumor stable on imaging (84 months from diagnosis). (E) Further tumor progression with increase in size of posterior midbrain mass (92 months from diagnosis). (F) Following radiation therapy, tumor appears stable in size although increased enhancement of the tumor was noted in the pons, midbrain and subthalamic regions (105 months from diagnosis). (G) Tumor stable on most recent evaluation (152 months from initial diagnosis).
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case_images: MRI brain revealed a heterogeneously enhancing mass in the fourth ventricle with obstructive hydrocephalus ( Figures 1 ,  2A ). The patient's treatment included endoscopic third ventriculostomy and subtotal tumor resection ( Figure 2B ). Local tumor progression was identified on surveillance imaging 5 years after initial diagnosis ( Figure 2C ). She completed a 70-week course of chemotherapy as planned, with subsequent tumor stability ( Figure 2D ). Approximately 8 months post chemotherapy, the patient developed further clinical and radiographic progression with vomiting and headaches ( Figure 2E ). Neuro-imaging ruled out a stroke and demonstrated stability in tumor size, with new T2 changes and enhancement surrounding the tumor ( Figure 2F ). T2 changes and enhancement ( Figure 2G ) suggesting the initial changes were related to pseudoprogression. The patient continued to endorse headaches, diplopia, hearing impairment, tinnitus, ataxia, and fatigue.
case_images: Proton radiation plan demonstrating doses administered. Coronal (A), axial (B) and sagittal (C) images demonstrating proton radiation plan and doses administered.
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case_images: Subsequent treatment options were discussed and ultimately the patient proceeded with focal proton beam radiation (5220cGy/29 fractions) ( Figure 3 ).