Cranio-cervical growth collision: another explanation of the Arnold-Chiari malformation and of basilar impression.

Analysis of neuro-cranio-spinal development suggests a cranio-cervical growth conflict as the cause of the Arnold-Chiari malformation and of basilar impression. The ascending course and elongation of the upper cervical nerves associated with the Arnold-Chiari malformation reflects the abnormal, caudo-cranially proceeding growth of the cervical spine. This is the opposite of the normal cranio-caudal direction of growth (which includes the brain) with downward slanting of the cervical nerve roots. The cervical growth reversal is a compensatory event related to the impairment of distal spinal growth at the level of the coexistent myelomeningocele. With the reversal of the cerical growth, the initial descent (uncoiling) of the primordial brain curvatures is compromised owing to the growth-collision with the ascending cervical spine. Their subsequent growth proceeds into the upper cervical spinal canal. The contents of the posterior cranial fossa are actively "sucked up", "devoured" by the latter. In contrast to the adaptively enhanced growth of the early cranio-cervical nervous structures in the Arnold-Chiari malformation, as an answer to the growth-shifts of the encasing skeleton, basilar impression is a postembryonic adaptation of the cervico-cranial skeleton to the inadequate growth of the nervous structures after the latter have lost their growth adaptability. Arnold-Chiari malformation and basilar impression are just two representatives of "osteo-neural growth pathology" encompassing some "dysplastic" disorders of the axial as well as of the limb skeleton such as platyspondyly, scoliosis, Scheuermann's kyphosis, achondroplasia-like conditions, congenital dysplasia of the hip etc.(ABSTRACT TRUNCATED AT 250 WORDS)