Sagittal T1 MRI without contrast of the brain (above left) shows a cystic lesion in the inferior posterior fossa which is not causing any mass effect in a normally sized posterior fossa. Coronal T2 MRI (above right) and axial T1 MRI without contrast (below) show a mildly enlarged fourth ventricle which is connecting to the cystic lesion due to mild agenesis of the cerebellar vermis.
