Enlarged cisternae magnae and posterior fossa cysts simulating Dandy-Walker syndrome on computed tomography.

Computed tomography was performed on 5 children with posterior fossa cystic abnormalities. On an axial tomogram, an enlarged cisterna magna could not be distinguished from a Dandy-Walker variant, nor could an encysted fourth ventricle be distinguished from a subarachnoid cyst. Supplementary air encephalography or sagittal reconstruction of tomograms is necessary to define posterior fossa cysts accurately.