Toddler with cervical adenopathy with an incidental finding on a neck CT exam

MRI of Dandy Walker malformation
Sagittal T1 MRI without contrast of the brain (upper left) shows an enlarged posterior fossa containing a dilated fourth ventricle resulting in a large midline cyst that is causing elevation of the superior cerebellum and torcular inversion. Axial (upper right) and coronal (below) T1 MRI without contrast of the brain show agenesis of the cerebellar vermis. A mild-moderate amount of hydrocephalus is present.

The diagnosis was Dandy Walker Malformation.