Cranial settling

Cranial settling is a condition in which erosive changes of the atlantal lateral masses result in downward telescoping of the atlas onto the axis body, anterior displacement of the atlantal posterior arch, and subsequent ventral and dorsal cervicomedullary compression.

Basilar impression occurs when parts of the cervical (neck) vertebrae enter the hole in the skull base (foramen magnum).

Basilar invagination is the same problem, except that it’s caused by softening in the bones at the skull base.

Cranial settling occurs when the bone at the top of the neck on which the skull rotates (dens) extends into the foramen magnum.