Chiari Malformation Type 1

Excerpt

Chiari malformations are defined as a spectrum of hindbrain abnormalities involving the cerebellum, brainstem, skull base, and cervical cord. According to the type of herniation of the brain tissue displaced in the spinal canal and the characteristics of the anomalies of the brain or spine development, 4 types of Chiari malformations have been classified. Together with basilar invaginations, Chiari malformations represent the most common craniocervical junction malformations seen in adults. At the end of the nineteenth century, the pathologists Julius Arnold (1835-1915) and Hans Chiari (1851-1916) were the first to describe the condition as a complex clinical and pathological condition involving deformity of the cerebellum and brainstem in children.

Among Chiari malformations, Chiari type 1 malformation is the more common variant. Chiari 1 malformation is characterized by the caudal descent of the cerebellar tonsils through the foramen magnum. However, there is no accepted universal definition amongst clinicians as the malformation shows incongruity in clinic radiological correlation. Some authors, for example, have recently proposed to refer to the Chiari 1 malformation as "Chiari syndrome," while the term malformation should be reserved for types 2 to 3. (see Image. Chiari Malformation Types 1 and 2). Clinically, Chiari 1 malformation can be an asymptomatic hindbrain hernia or manifest from late childhood to adulthood with tussive headaches and focal neurological manifestations. On the other hand, Chiari types 2, 3, and 4 are congenital and clinically significant. The nosographic collocation of type 0 or 0.5 Chiari malformation or Chiari-like symptoms without tonsillar herniation, type 1.5 Chiari malformation between types 1 and 2, and complex Chiari is controversial and not universally accepted. (see Table. Chiari Malformation Types).