Clivus (anatomy)

Behind the dorsum sellæ is a shallow depression, the clivus, which slopes obliquely backward, and is continuous with the groove on the basilar portion of the occipital bone; it supports the upper part of the pons.

Relation of the clivus and dens
The clivus is an important landmark for checking for anatomical atlanto-occipital alignment; the clivus, when viewed on a lateral C-spine X-ray, forms a line which, if extended, is known as the known as Wackenheim's clivus line. Wackenheim's clivus line should pass through the dens of the axis or be tangential to it.