Bony observations of some morphological variations and anomalies of the craniovertebral region.

Human skeletons (214) belonging to a South African black and white cadaver population were pooled and examined for malformations of the craniovertebral region. Four crania, presenting with various manifestations of an occipital vertebra, such as a paracondylar process, epicondylar process, hypocondylar arch, and a third condyle were identified as well as two crania showing various degrees of assimilation of the atlas to the basicranium. Of particular interest was the identification of a cloverleaf-shaped foramen magnum in a cranium of an individual with achondroplasia as well as a cranium with marked asymmetry of both foramen magnum and occipital condyles. Due to the availability of both cranium and corresponding atlanto-axial components, the clinical significance of certain aspects of craniovertebral anomalies were vividly demonstrated, such as a pseudarthrosis formed by the meeting of a paracondylar process with an epitransverse process and a dens "riding high" in the foramen magnum as a result of assimilation of the atlas.