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Chiari malformation is a problem with the structures at the back of the brain. An area of the brain called the cerebellum normally sits inside the back of the skull. In Chiari malformation, the cerebellum sits partially or fully below the skull. This position can put pressure on the cerebellum, nearby brainstem, and upper spinal cord. It can also block the flow of cerebrospinal fluid (CSF) around the brain and spinal cord. CSF normally cushions the brain and spine. When it becomes blocked, it can cause a buildup of pressure in the brain and spinal cord.
There are 4 types of Chiari malformations. The types are based on the severity of the disorder and the parts of the brain that protrude into the spinal canal.
Chiari malformation is most often caused by a problem in the formation of the skull before birth. It is not clear why the skull does not develop normally, but it may be due to genetics or the health of the mother during pregnancy. The back of the skull normally has a curved area for the cerebellum and brainstem to sit in. In some babies, the space is too small for the brain to properly sit in and the cerebellum and brain stem are pushed downward into the spinal canal.
Type 1 Chiari malformation, the most common type, usually presents in older children, adolescents, and sometimes adults.
Type 3 is usually present at birth and is usually associated with hydrocephalus.
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There are no known risk factors for Chiari malformation. There may be a genetic connection in some families.
Both the position of the brain and problems with CSF flow can cause a range of neurological symptoms that vary based on type. Those with type I may never have symptoms. When symptoms do occur, headaches are a hallmark symptom.
Symptoms may include:
Symptoms in infants with type 2 or 3 may include:
Type 1 may be suspected based on symptoms or discovered accidentally during tests for other conditions or injuries. Type 2 and 3 may be suspected when associated defects are present or symptoms are present.
If someone is experiencing symptoms, a doctor will ask about symptoms and medical history. A physical exam will be done which may include cognitive tests of memory, reflexes, or motor skills. Imaging tests may be done to evaluate the brain and skull. Tests may include:
Special studies may also be done to evaluate the flow of fluid around the brain and spinal cord.
Chiari Type 1 malformations that do not cause symptoms do not require treatment. Those that do cause symptoms will be treated based on individual symptoms and the degree of pressure on the brain. Medication may be recommended to help manage headaches and pain.
Treatments to help manage symptoms that interfere with everyday life may include:
Severe compression of brain tissue, a buildup of pressure in the brain or spinal cord, and types 2 and 3 will require surgery to prevent further damage. Surgical options may include:
Multiple surgeries may be needed.
There is no known way to prevent Chiari malformation. Genetic counseling may help parents of a child with this condition to determine the risk in future children.
American Syringomyelia and Chiari Alliance Project
National Institute of Neurological Disorders and Stroke
Canadian Neurological Sciences Federation
Chiari malformation. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T115525/Chiari-malformations. Updated May 10, 2017. Accessed February 16, 2018.
Chiari malformation fact sheet. National Institute of Neurological Disorders and Stroke website. Available at: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Chiari-Malformation-Fact-Sheet. Accessed February 16, 2018.
Chiari malformation. American Association of Neurological Surgeons website. Available at: http://www.aans.org/patient%20information/conditions%20and%20treatments/chiari%20malformation.aspx. Accessed February 16, 2018.
Chiari malformation. Columbia University Medical Center website. Available at: http://www.columbianeurosurgery.org/conditions/chiari-malformation/. Accessed February 16, 2018.
Hekman KE, Aliaga L, et al. Positive and negative predictors for good outcome after decompressive surgery for Chiari malformation type 1 as scored on the Chicago Chiari Outcome Scale. Nuerol Res. 2012;34(7):694-700.
Last reviewed March 2018 by EBSCO Medical Review Board Rimas Lukas, MD Last Updated: 2/20/2017