ACM.II

Arnold Chiari Malformation _Type II


The Austrian pathologist Hans Chiari in the late 1800s described seemingly related anomalies of the hindbrain, the so called Chiari malformations I, II and III. Later, other investigators added a fourth (Chiari IV) malformation. The scale of severity is rated I - IV, with IV being the most severe. Types III and IV are very rare. * The most common form of Arnold-Chiari Malformation is Type I, which is generally asymptomatic during childhood, but often manifests with headaches and cerebellar symptoms. * Type II is usually accompanied by a myelomeningocele leading to partial or complete paralysis below the spinal defect. Abnormal development of the cerebellar vermis and medulla occur, and they both descend into the foramen magnum. Hydrocephalus is also nearly always present. * Type III causes severe neurological defects. It is associated with an encephalocele. * Type IV involves a failure of brain development. Other conditions sometimes associated with Chiari Malformation include hydrocephalus,syringomyelia, spinal curvature, and connective tissue disorderssuch as Ehlers-Danlos syndrome and Marfan Syndrome.