Two Calves of Arnold-Chiari Malformation and Their Craniums

Abstract

Two calves with Arnold-Chiari malformation were examined macroscopically. The brain and cranium appeared to be compressed dorso-ventrally and parts of the cerebellum, medulla oblongata and fourth ventricle herniated through the enlarged foramen magnum to the vertebral foramen of the atlas. The internal cranial base composed of the sphenoid and occipital bones was abnormally flat, so the hypophyseal fossa and dorsum sellae were obscure. It was considered that the malformation probably resulted primarily from an abnormal development of these bones, the osteogenesis of which was induced by the notochord, and the brain secondly showed its abnormal shape and position.