The relationship between certain craniovertebral skeletal deformities and associated neural changes, while discussed in the literature with respect to its various phases, seems more and more to be a manifestation of different aspects of the same process. Thus, there are interrelated elements of similarity binding together the conditions of platybasia (flattened base with deformity of the foramen magnum), occipitalization of the atlas, the Klippel-Feil1 syndrome (defect of the atlas and sometimes fusion of one or more upper cervical vertebrae) and the Arnold-Chiari2 malformation (lengthening of the pons and medulla, with herniation of the cerebellum into the spinal canal) in their relation to syringomyelic conditions, hydrocephalus and spina bifida. The significance of the Arnold-Chiari malformation in association with hydrocephalus and spina bifida has been discussed by Russell and Donald,3 its appearance with hydrocephalus in the absence of spina bifida by McConnell and Parker4 and the association of