Mass in 4th ventricle: headache and emesis. Brain: There is a heterogeneous mass that contains patchy enhancement and multiple small cystic components within the fourth ventricle. The mass measures up to approximately 4 cm and results in marked compression of the brainstem and cerebellum with mild inferior cerebellar herniation. In addition, there is marked dilatation of the third and lateral ventricles with diffuse periventricular white matter T2 hyperintensity, which is compatible with transependymal cerebrospinal fluid flow. There is no evidence of acute intracranial hemorrhage or acute infarct. There is no midline shift. The major cerebral flow voids are intact. There is dilatation of the bilateral optic nerve sheaths. The skull is intact.Spine: There is no evidence of mass lesions or abnormal enhancement within the spinal canal. The vertebral column alignment is within normal limits. The vertebral body and disc space heights are preserved. The vertebral bone marrow signal is unremarkable. There is no significant spinal canal stenosis. The spinal cord displays normal signal and morphology and cauda equina appears to be intact. The paravertebral soft tissues are unremarkable.
1. A fourth ventricular mass measuring up to approximately 4 cm with associated obstructive hydrocephalus likely represents a medulloblastoma.2. No evidence of drop metastases in the spinal canal.