[Cranio-vertebral junction anomalies and osseous dysplasias (author's transl)].

The cartilaginously preformed occipital region of the cranium is ontogenetically a part of the backbone. The cranio-vertebral junction is unique among the other junctional areas of the backbone: 1. It has not yet been proved that different combinations of cranial and caudal junction anomalies are not combined with cervical junction anomalies. 2. The assimilations of the atlas which are considered to be progressive and regressive variants and the so-called manifestations of the occipital vertebra, i.e. diametrically opposed members of a developmental line occur together with a frequency that is inconsistent with the above assumption. 3. Both variants occur combined with the most serious developmental abnormalities of the cranio-vertebral junction. All described occipital-cervical abnormalities may have clinical significance with extends far beyond an assessment as simple variants (deviations) and includes extremely serious, life-threatening osseous deformations.