Chiari malformations (CMs) are structural brain abnormalities in the cerebellum (part of the brain that controls balance). CMs are generally thought to be congenital (present at birth), though sometimes may not become clinically apparent until adulthood. CMs may develop in the cavity at the base of the skull when the bony space is smaller than normal, causing the cerebellum and brainstem to be pushed down. This pressure on the cerebellum and brainstem can affect functions of these areas and possibly block the flow of cerebrospinal fluid to and from the brain. Symptoms of individuals with CMs may include neck pain, balance problems, muscle weakness, numbness in arms or legs, dizziness, difficulty swallowing, hearing loss and vision problems. Treatment may require a team of specialists including pediatricians, neurosurgeons, neurologists, eye specialists and other health professionals. Organizations exist to provide resources and support to individuals facing rare conditions. Information provided in part by our partner NORD.