Axial T2 images reveal a large high signal extra-axial lesion matching CSF
intensity which displaces the cerebellar and occipital hemispheres laterally.
Note that the floor of the fourth ventricle appears expanded by the lesion,
and the roof of the fourth ventricle is not seen.
Axial gadolinium-enhanced T1 (3) and coronal non-enhanced T1 (4) reveal
that the lesion does not enhance, again follows CSF in signal intensity, and
displaces the tentorium upward. The posterior fossa is enlarged, and the
calvarium is thinned adjacent to the lesion.
Key words: mri congenital developmental