Axial CT without contrast of the brain (above left) shows a primarily cystic lesion in the left cerebellar hemisphere that has a solid component posteriorly that contains calcification. There is mild to moderate obstructive hydrocephalus present. Axial (above right) and coronal (below left) T1 MRI with contrast of the brain shows a primarily cystic lesion in the left cerebellar hemisphere that has a solid component posteriorly that enhances. There is mild to moderate hydrocephalus present. Sagittal T1 MRI with contrast (below right) shows the cerebellar mass causing tonsillar herniation beneath the foramen magnum.
