Newborn with a posterior fossa cyst on prenatal ultrasound

MRI of mega cisterna magna
Sagittal (above left), coronal (above right), and axial (below) T1 MRI without contrast of the brain shows a prominent retrocerebellar cerebrospinal fluid space (the cisterna magna) with a normal vermis, normal 4th ventricle, and normal cerebellar hemispheres.

The diagnosis was mega cisterna magna.