Basilar invagination

What it means

Projection of the tip of the dens more than 5 mm above a line joining the hard palate to the posterior lip of the foramen magnum (Chamberlain's line) or the tip of the dens is greater than 7 mm above McGregor's line (the back of the hard palate to the lowest point of the occipital squama).

Rare diseases that can present with this3

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category