What is the most striking anatomical abnormality?
The posterior fossa is small and the brainstem and cerebellum low lying.
What is the likely diagnosis?
Chiari II malformation.
What is the appearance of the tectal plate known as?
Tectal beaking - the tectum is angulated with the aqueduct assuming a > configuration.
MRI of the brain demonstrates a small posterior fossa with low lying tentorial attachment posteriorly. The tectum is beaked and hydrocephalus is present.