How does occipitalization influence the dimensions of the cranium?

To describe occipitalization on human dry skulls and to compare craniofacial morphology including the posterior cranial fossa in skulls with occipitalization and in skulls without occipitalization and with normal craniofacial morphology (controls).

A total of 29 skulls were selected from the Björk collection. Nine had occipitalization of atlas. Twenty had no dentoalveolar or craniofacial anomalies, and no occipitalization was visible on the skulls (controls). The ages of the skulls were between adolescence and adulthood.

Visual assessments to describe the occipitalization pattern, direct measurements to measure the foramen magnum dimensions and cephalometric radiographic analyses to describe the craniofacial morphology. New variables were determined to describe the posterior cranial fossa.

Of the skulls with occipitalization, 67% had complete and 33% had partial occipitalization. In the posterior part of the neural arch, 44% had a cleft. Occipitalization was significantly associated with a small foramen magnum (p < 0.01; p < 0.001) and deviant shape of the posterior cranial fossa (p < 0.05). The craniofacial morphology in the vertical and sagittal dimensions including the cranial base angle was normal in skulls with occipitalization, which indicates that occipitalization is associated with deviant morphology of the surrounding bony structures but not with deviations in the craniofacial morphology in general. The results of this study are important for the diagnosis of occipitalization on 2D radiographs.