Platybasia and the Arnold-Chiari malformation.

Abstract

PLATYBASIA and the Arnold-Chiari deformity are of concern to the ophthalmologist. Not only are the ocular signs and symptoms of these entities often the presenting complaints but, equally important, they simulate those of multiple sclerosis, tumor of the brain stem or cerebellum, and other lesions of the posterior fossa, which have an entirely different prognostic and therapeutic significance. Since these conditions have not received general recognition in the ophthalmological literature,* it will be the purpose of this communication to describe the abnormalities as represented in the pertinent literature and to present several cases studied by us with emphasis on the ophthalmological aspects. The abnormality variously called platybasia, flat skull, or basilar impression consists of an upward bulge or invagination of the occiput in the region of the foramen magnum.† There is usually a partial fusion of the upper cervical vertebrae to the skull and to each other, with a protrusion