Upright MRI was more than twice as sensitive as standard MRI, likely because gravity affects cerebellar position.Cases of congenital Chiari malformation may be explained by evolutionary and genetic factors. Typically, an infants brain weighs around 400g at birth and triples to 1100-1400g by age 11. At the same time the cranium triples in volume from 500 cm3 to 1500 cm3 to accommodate the growing brain. During human evolution, the skull underwent numerous changes to accommodate the growing brain. The evolutionary changes included increased size and shape of the skull, decreased basal angle and basicranial length. These modifications resulted in significant reduction of the size of the posterior fossa in modern humans. In normal adults, the posterior fossa comprises 27% of the total intracranial space, while in adults with Chiari Type I, it is only 21%. H. neanderthalensis had platycephalic (flattened) skulls. Some cases of Chiari are associated with platybasia (flattening of the skull base). History
The history of Chiari malformation is described below and categorized by the year:

1883: Cleland was the first to describe Chiari II or Arnold–Chiari malformation on his report of a child with spina bifida, hydrocephalus, and anatomical alterations of the cerebellum and brainstem. 1891: Hans Chiari, a Viennese pathologist, described the case of a 17-year-old female with elongation of the tonsils into cone shaped projections which accompany the medulla and are crammed into the spinal canal.
Notable people
Rosanne Cash – U.S. singer-songwriter; daughter of Johnny Cash
Julia Clukey – U.S. luge competitor for Team USA in 2010 Vancouver Winter Olympics
Joanna David – British television and stage actress
J. B. Holmes – U.S. professional golfer
Marissa Irwin – U.S. fashion model with Chiari secondary to Ehlers-Danlos syndrome
Bobby Jones – U.S. World Golf Hall of Fame golfer and founder of the Augusta National Golf Club
Allysa Seely – U.S. Gold Medalist at the 2016 Summer Paralympics in the paratriathlon
Leah Shapiro – U.S. drummer for the band Black Rebel Motorcycle Club
Michelle Stilwell – Canadian wheelchair racer and politician
Rachid Taha – Algerian singer
Sabre Norris – Australian skateboarder and surfer

See also

Hypermobility spectrum disorder


== References ==