Figure 2.

Schematic framework of selected CM traits (red lines) and “normal” traits (blue lines) to illustrate underlying anatomical differences in the caudal cranium and cranial cervical vertebrae. The red (SM affected) lines are superimposed on those for representing normal (blue) and aligned along the skull base at fixed point “*”, the dorsum of spheno-occipital synchondrosis. The basisphenoid, possibly the presphenoid, is flexed dorso-caudally (“sphenoid flexure”). The cranial cervical vertebrae are more rostral, with the odontoid process, angled ventrally with medullary elevation (“cervical flexure”).