(Arnold-Chiari Malformation; Arnold-Chiari Syndrome; Type 2 Chiari Malformation; Cerebellomedullary Malformation Syndrome)
by Cynthia M. Johnson, MA
Chiari malformations are problems with the structures at the back of the brain. A part of the brain called the cerebellum normally sits inside the back of the skull. This problem causes it to sit partially or fully below the skull. This can put pressure on the cerebellum, brainstem, and spinal cord. It can also block the flow of cerebrospinal fluid (CSF) and cause pressure around the brain and spinal cord.
There are four types:
Chiari malformation is most often caused by a problem in the way the skull forms before birth. It is not known why this happens. Genes may play a role.
There are no known risk factors for this health problem. It may run in some families.
People with type 1 may not have symptoms. Others may have symptoms based on the position of the brain and problems with CSF flow.
Babies may have:
Older children and adults may have:
The doctor may ask about your symptoms and health history. A physical exam will be done. This may be enough to suspect Type 1. It may also be found during tests for other health problems.
Type 2 and 3 may be suspected in a child who has other birth defects and symptoms.
Images may be taken to confirm the diagnosis. This can be done with an MRI scan.
People with type 1 may not need to be treated unless they have problems. People who do have problems will be treated based on their symptoms and the amount of pressure on their brain.
The goal of treatment is to manage problems that get in the way of daily life. Options are:
People with severe problems and those with types 2 and 3 will need surgery. More than one surgery may be needed. Some options are:
There are no current guidelines to lower the risk of this health problem.
American Syringomyelia and Chiari Alliance Project
National Institute of Neurological Disorders and Stroke
Canadian Neurological Sciences Federation
Chiari malformation. American Association of Neurological Surgeons website. Available at: https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Chiari-Malformation. Accessed April 7, 2020.
Chiari malformation. Columbia University Medical Center website. Available at:
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Accessed April 7, 2020.
Chiari malformation. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/chiari-malformation/ . Updated May 10, 2017. Accessed April 7, 2020.
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. Updated March 13, 2020. Accessed April 7, 2020.
Last reviewed February 2020 by EBSCO Medical Review Board Rimas Lukas, MD
Last Updated: 4/7/2020