Chiari malformation

Chiari malformation is a structural defect of the cerebellum in which one or both cerebellar tonsils sink down through the foramen magnum, the opening at the base of the skull. It can cause headaches, trouble swallowing, vomiting, dizziness, neck pain, unsteady gait, poor hand coordination and numbness or tingling in the hands and feet, and sometimes hydrocephalus when the flow of cerebrospinal fluid is blocked. The headache is typically at the back of the head and worsened by coughing or straining. It is named for the Viennese pathologist Hans Chiari, who described it in 1891, and the type II form is also called Arnold-Chiari malformation. Diagnosis rests on neurological examination and magnetic resonance imaging, and surgery decompresses the area when symptoms warrant it.