Chiari malformations are normally caused due to structural defects in the brain or spinal cord, these defects occur during the fetal development phases. But Chiari malformation can also occur in later stages of life. if there is any injury or exposure to toxic substances this can result in drainage of an excessive amount of cerebrospinal fluid, the fluid which protects the brain and spinal cord. Chiari malformation is considered a congenital condition, although acquired forms of the condition have been diagnosed. In the 1890s, a German pathologist, Professor Hans Chiari, first described abnormalities of the brain at the junction of the skull with the spine. He categorized these in order of severity; types I, II, III and IV. The term “Arnold-Chiari” was latter applied to the Chiari type II malformation. These malformations, along with syringomyelia and hydromyelia, two closely associated conditions, are described below. The cerebellum controls the coordination of motion and is normally located inside the base of the skull, in what is referred to as the posterior fossa. Usually, the cerebellum is composed of two lateral halves, or hemispheres, and a narrow central portion between these hemispheres, known as the vermis. Along the under surface of the hemispheres, there are two small protrusions called the tonsils. The fourth ventricle is a space filled with cerebrospinal fluid (CSF) located in front of the cerebellum (and behind the brainstem). All of these structures are located just above the foramen magnum, the largest opening at the base of the skull through which the spinal cord enters and connects to the brainstem.