Predominantly solid lesion with small areas of cystic degeneration / necrosis is seen in posterior fossa in midline. Lesion is expanding the 4th ventricle, splaying brainstem anteriorly and indenting bilateral middle cerebellar peduncles. No obvious extension of lesion is seen into foramen of Magendie or Luschka. Diffusion restriction is seen with low ADC.
Obstructive hydrocephalus is seen with periventricular seepage.
On MR spectroscopy, a tall choline peak is seen suggesting neoplastic etiology.