What poor prognostic feature is evident? Is this common?
CSF dissemination is present, most easily seen in the floor of the third ventricle on sagittal images. CSF seeding is present in ~15% of cases at the time of diagnosis.
MRI obtained a number of weeks earlier (before the VP shunt was inserted) demonstrates a large pineal region mass with intermediate signal intensity on T2W images. Hydrocephalus and periventricular CSF flow (interestitial edema) are also visible.
Post contrast T1W images shows mildly heterogenous but vivid enhancement with invasion to the quadrigeminal plate, third ventricle and superior cerebellum.
Two regions of ependymal enhancement are seen in frontal horns of lateral ventricles as well as filling of the infundibular and supraoptic recesses of the third ventricles. Leptomeningeal enhancement is also prominent elsewhere. These are in keeping with ependymal dissemination.