• Chiari Malformation

    (Arnold-Chiari Malformation; Arnold-Chiari Syndrome; Type II Chiari Malformation; Cerebellomedullary Malformation Syndrome)


    Chiari malformation is a problem with the structures at the back 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 cerebellum, nearby brainstem, and upper spinal cord. The low position can also block the flow of cerebrospinal fluid (CSF) around the brain and spinal cord. CSF normally cushions the brain and spine but when it becomes blocked it can cause a buildup of pressure in the brain and spinal cord. Both the position of the brain and problems with CSF flow can cause a range of neurological symptoms such as headaches, weakness, or problems with coordination.
    There are four different types of chiari malformations based on the type and amount of tissue that has passed to the spinal canal.


    Chiari malformation is most often caused by a problem in the formation of the skull before birth. The back of the skull normally has a curved area for the cerebellum and brainstem to sit in. In some babies, this area of the skull does not develop well and the space is too small for the brain to properly sit in. The cerebellum and brain stem are pushed downward into the spinal canal by the abnormal shape of the skull. It is not clear why the skull does not develop normally but it may be due to genetics or health of the mother during pregnancy.
    Rarely chiari malformation develops later in life. In this case it may be caused by a loss of CSF or an injury or infection of the neck or chest.
    Brain Stem and Lower Brain
    GM00010 97870 brainstem.jpg
    Copyright © Nucleus Medical Media, Inc.

    Risk Factors

    There are no known risk factors for chiari malformation. There may be a genetic connection in some families.


    Some may never have symptoms. Others who have the malformation at birth may not develop symptoms until later in life. Symptoms will depend on the amount and type of tissue involved but can include:
    • Lightheadedness
    • Fainting
    • Weakness in the legs
    • Headaches—may be made worse with coughing
    • Inability to hear or ringing in the ears
    • Eye problems such as difficulty seeing, eye pain, and rapid eye movement
    • Poor coordination
    • Uncontrolled shaking or trembling
    • Difficulty walking
    • Numbness or tingling in the arms or legs
    Symptoms in infants may include:
    • Vomiting
    • Weakness
    • Paralysis of the limbs
    • Choking
    • Chronic cough or hoarseness
    • Irritability, especially during feeding


    The malformations may be discovered accidentally during tests for other conditions or injuries.
    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 your brain and spinal cord.


    Chiari malformation 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:
    • Physical or occupational therapy can help improve muscular coordination and trembling. Braces or a wheelchair may also be needed.
    • Speech therapy for speech or swallowing problems.
    Severe compression of brain tissue or a build up of pressure in the brain or spinal cord will require surgery to prevent further damage. Surgical options may include:
    • Sections of bone from the skull or vertebrae may be removed. The removal of bone sections may help relieve pressure on the affected tissue.
    • Tissue that surrounds the brain and spinal cord may be opened to examine the brain and spinal tissue. The tissue may then be expanded to improve the flow of CSF.
    • A shunt may be placed that allows extra CSF to drain from the brain or spine into the chest or abdomen.
    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 http://www.asap.org

    National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov


    Canadian Neurological Sciences Federation http://www.cnsfederation.org

    Health Canada http://www.hc-sc.gc.ca


    Chiari malformation. Comer Children’s Hospital website. Available at: http://www.uchicagokidshospital.org/online-library/content=P02592. Accessed February 12, 2014.

    Chiari malformations. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115525/Chiari-malformations. Updated September 11, 2015. Accessed September 28, 2016.

    Chiari malformation information page. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/chiari/chiari.htm. Updated April 5, 2016. Accessed May 4, 2016.

    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.

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