There is a midline extra-axial expansile lesion is presumably in the 4th ventricle measuring 4.8 x 3.7 cm. There is mass effect on cerebellar hemispheres laterally, and medulla and upper spinal cord anteriorly but no hydrocephalus or significant vasogenic edema. There is no considerable enlargement of the foramen of Luschka bilaterally to suggest their involvement. The lesion is heterogeneously hypodense with small calcified foci in the anteroinferior aspect.