Chiari malformation

In neurology, the Chiari malformation ( kee-AR-ee; CM) is a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum (the opening at the base of the skull). CMs can cause headaches, difficulty swallowing, vomiting, dizziness, neck pain, unsteady gait, poor hand coordination, numbness and tingling of the hands and feet, and speech problems. Less often, people may experience ringing or buzzing in the ears, weakness, slow heart rhythm, fast heart rhythm, curvature of the spine (scoliosis) related to spinal cord impairment, abnormal breathing such as in central sleep apnea, and, in severe cases, paralysis. CM can sometimes lead to non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid (CSF) outflow. The CSF outflow is caused by phase difference in outflow and influx of blood in the vasculature of the brain. The malformation is named after the Austrian pathologist Hans Chiari. A type II CM is also known as an Arnold–Chiari malformation after Chiari and German pathologist Julius Arnold.