What is arnold-chiari malformation?Arnold-Chiari malformation is a condition in which the back of the brain (cerebellum) extends down into the upper spinal canal. Children are usually born with this malformation, but it also can develop later in childhood.
There are four types of Arnold-Chiari malformation. Chiari I malformation is the most common type. Chiari type 1 malformations (CM1) occur in the region where the brain and the spinal cord join. In this disorder, the portions of the brain called the cerebellum and/or brainstem lie lower than usual. Often, a portion of the cerebellum called the cerebellar tonsils protrudes out of the base of the skull into the spinal canal. This protrusion causes pressure in the brain, contributing to the symptoms people experience. Chiari II, commonly referred to as the Arnold-Chiari Malformation, is found almost exclusively in children with spina bifida. Chiari type III and IV malformations are extremely rare. References to a Chiari 0 malformation may be found but all physicians who treat Chiari malformations have not accepted this name.Chiari malformation may be associated with many other anomalies including myelomeningocele, syringomyelia, and spina bifida. Hydrocephalus (increased intracranial pressure) may also occur.
Professor Hans Chiari was a German pathologist who first described these abnormalities of the brain at the junction of the skull with the spine in 1890. Another doctor, Arnold, later added to the type II description, hence the name “Arnold-Chiari Malformation.” Of the four classifications of Chiari, only two types of the malformation have practical importance, commonly referred to as Chiari type I and Chiari type II.