What is Chiari Malformation

Arnold-Chiari Malformation is a condition in which the cerebellum portion of the brain protrudes into the spinal canal. It may or may not be apparent at birth. Arnold-Chiari I type malformation usually causes symptoms in young adults and is often associated with syringomyelia, in which a tubular cavity develops within the spinal cord. Arnold-Chiari II type malformation is associated with myelomeningocele (a defect of the spine) and hydrocephalus (increased cerebrospinal fluid and pressure within the brain), which usually are apparent at birth. Myelomeningocele usually causes paralysis of the legs and, less commonly, the arms. If left untreated, hydrocephalus can cause mental impairment. Either type of Arnold-Chiari Malformation can cause symptoms of headache, vomiting, difficulty swallowing, and hoarseness.

Professor Hans Chiari was a German pathologist who first described these abnormalities of the brain at the junction of the skull with the spine in 1890. Another doctor, Arnold, later added to the type II description, hence the name “Arnold-Chiari Malformation.” Of the four classifications of Chiari, only two types of the malformation have practical importance, commonly referred to as Chiari type I and Chiari type II.

Usually symptoms of Chiari malformations do not appear until early adutlhood but can occasionally be seen in young children. Some common symptoms include headaches, neck pain, dizziness, vision problems, balance problems and muscle weakness. Other symptoms include difficulty swallowing, frequent gagging and choking and, in some cases sleep apnea may be present.Adults and adolescents who are unaware they have Arnold-Chiari I type malformation may develop headache that is predominantly located in the back of the head and is increased by coughing or straining. Symptoms of progressive brain impairment may include dizziness, an impaired ability to coordinate movement, double vision, and involuntary, rapid, downward eye movements.

Infants and children with myelomeningocele may require surgery to repair protrusion of the meningeal sac into the spinal cord. Hydrocephalus may be treated with surgical implantation of a shunt to relieve increased pressure on the brain. Some adults with Arnold-Chiari Malformation may benefit from surgery in which the existing opening in the back of the skull is enlarged.

Infants with very severe malformations may have life-threatening complications. Most patients who have surgery experience a reduction in their symptoms. Some patients may experience prolonged periods of relative stability.

Research supported by the NINDS includes studies to understand how the brain and nervous system normally develop and function and how they are affected by disease and trauma. These studies contribute to a greater understanding of congenital birth defects, such as Arnold-Chiari Malformation, and open promising new doors to potential treatments.