History of large posterior fossa ependymoma WHO grade 2 s/p resection x2 with VP shunt placement and adjuvant proton radiotherapy who presents for post-operative management following stereotactic cyst puncture and insertion of Rickham catheter. Following radiation therapy, the patient formed a large cystic structure in the former resection cavity in the right cerebellopontine angle. Subsequently, the patient developed a 7th nerve palsy and compression of the brainstem with right side weakness. Interval surveillance MRI. There are postsurgical changes of right occipital craniotomy. The right occipital approach catheter traversing the right CP angle cystic lesion is unchanged in position. There has been interval increase in size of one of the cystic components at the right CP angle. For example, a component just lateral to the catheter tip measures up to 23 mm (series 501, image 10), previously 12 mm. The enhancing posterior fossa mass appears slightly larger when compared to prior measuring approximately 49 x 44 mm (series 1301, image 9). Comparable measurements on the prior MRI are difficult given differences in mass effect and surrounding parenchymal morphology. Mass effect on the brainstem with leftward deviation is unchanged. Left frontal approach ventriculostomy catheter terminates at the foramen of Monro, unchanged. The ventricle size has decreased in size compared to the prior exam. The right frontal horn measures 2 mm, previously 5 mm. Additional prior bilateral catheter tracts are noted. Flow voids are present within the major vessels indicating patency. Partial opacification of the bilateral mastoid air cells.
1. Slight interval increase in size of posterior fossa enhancing mass. 2. Reaccumulation of fluid in the cystic lesional components at the right cerebellopontine angle.