THE CLINICAL importance of developmental anomalies and malformations of the cervicomedullary juncture is being increasingly appreciated in neurological and neurosurgical centers. The most frequent of these processes is the Arnold-Chiari malformation (caudal displacement of brain stem, cerebellum, and spinal cord), as the fairly considerable number of articles on this subject in the recent literature will attest.
Nevertheless, there are still great disagreement on the pathogenesis of the Arnold-Chiari malformation and little concurrence on the relation of platybasia and spina bifida. Discussion continues on the role of this process in the hydrocephalus of infants with spina bifida. The historical data, the findings on examination, or roentgenographic evidence which should suggest the diagnosis in the adult patient, and the methods for elucidating the proof of diagnosis, remain poorly delineated. In surgical therapy results have been variable, but here at least the majority of writers (though by no means all) have eventually agreed upon an operative