A lobulated midline heterogeneously enhancing mass ( 29 x 38 mm ) extending inferiorly from the tentorium is again demonstrated. It is mildly heterogeneously T2 hypointense. There is prominent restricted diffusion within the mass. A cleft of CSF extends around the mass separating it from the cerebellum, suggesting it is extra-axial, although in the cerebellum this can be a difficult distinction to make. The mass effaces the fourth ventricle causing hydrocephalus. Ventricular size is stable and there is evidence of a small amount of transependymal oedema. Mass effect displaces pons anteriorly effacing the prepontine cistern and the cerebellar tonsils inferiorly through the foramen magnum (4 mm ).
MR venography and post contrast imaging demonstrates a normally enhancing superior sagittal sinus and a dominant right transverse sinus. The left transverse sinus is partially hypoplastic.