Chiari Malformation Type 1

At the end of the 19th century, 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 cerebellar and brainstem deformities in children. Chiari malformations are defined as a spectrum of hindbrain abnormalities involving the cerebellum, brainstem, skull base, and cervical spinal cord. Different subtypes of Chiari malformations have been identified, based on the degree and contents of herniated tissue (see  Chiari Malformation Types). Among the various types, the Chiari type 1 malformation is the most common subtype. Chiari 1 malformations are characterized by the caudal descent of the cerebellar tonsils through the foramen magnum of at least 5 millimeters. (see  Chiari Malformation Types 1 and 2). Clinically, Chiari type 1 malformations may be asymptomatic or manifest from childhood to adulthood with tussive headaches, sleep disordered breathing, scoliosis, and focal neurological deficits. On the other hand, Chiari types 2, 3, and 4 are congenital and present much earlier in life than Chiari type 1 malformations.