Chiari I “malformation”—an acquired disorder?

Abstract

Caudal herniation of the human hindbrain, indistinguishable from the Chiari I deformity, may occur after the establishment of spinal subarachnoid shunts and become symptomatic years after the procedure. Examples are presented. The force responsible for the displacement is probably the difference in pressure between the cranial and spinal compartments. On the basis of these observations and other considerations, a similar process, disproportionate absorption of CSF from the spinal region, might account for the spontaneous form of the Chiari I deformity.