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Disease Profile

Chiari malformation type 2

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Arnold-Chiari malformation; Chiari type II malformation; Chiari malformation type II;


Congenital and Genetic Diseases; Nervous System Diseases


Chiari malformation type 2 (CM type II) is a type of Chiari malformation in which both the cerebellum and brain stem tissue extend into the foramen magnum (the hole at the skull base for passing of the spinal cord).[1] CM type II is usually accompanied by a myelomeningocele (a form of spina bifida that occurs when the spinal canal and backbone do not close before birth), which can result in partial or complete paralysis of the area below the spinal opening.[1] While the severity of CM type II can vary greatly, it can potentially cause severe, life-threatening complications during infancy or childhood.[2] 

The exact cause of CM type II is not known but it appears to be due to defects in the brain and spinal cord that occur during fetal development.[2] Treatment includes surgery to ease symptoms and/or stop the progression of damage to the nervous system. For most people, surgery improves or stabilizes symptoms. Some people may require more than one surgery.[1]


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
30%-79% of people have these symptoms
Agenesis of corpus callosum
Percent of people who have these symptoms is not available through HPO
Arnold-Chiari malformation
Bulbar signs
Cervical myelopathy
Blue discoloration of the skin
Poor swallowing
Swallowing difficulties
Swallowing difficulty

[ more ]

Feeding difficulties
Feeding problems
Poor feeding

[ more ]

Generalized hypotonia
Decreased muscle tone
Low muscle tone

[ more ]

Gray matter heterotopia
Too much cerebrospinal fluid in the brain
Inspiratory stridor
Limb muscle weakness
Limb weakness
Multifactorial inheritance
Muscular hypotonia
Low or weak muscle tone
Involuntary, rapid, rhythmic eye movements
Occipital neuralgia
Fluid-filled cyst in spinal cord


People with Chiari malformation type II are typically treated with surgery. Surgery may include closure of open neural tube defects shortly after birth, treatment for hydrocephalus (most often by use of a shunt), and posterior fossa decompression (creating more space for the cerebellum and relieving pressure on the spinal cord). Medical issues may involve management of neurogenic bowel and bladder, neonatal feeding difficulties, respiratory failure, and apnea.[3]

As with any form of surgery, there are risks associated with surgery to treat Chiari malformations. Sometimes, surgery leads to no improvement or even worsening of symptoms.[4] For example, if nerve injury in the spinal canal has already occurred, surgery will not reverse the damage.[5] However, most people who have surgery have improvement of symptoms afterwards. Even if symptoms do not improve significantly, surgery might prevent existing symptoms from worsening.[4]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Chiari malformation type 2. Click on the link to view a sample search on this topic.


        1. Chiari Malformation Fact Sheet. National Institute of Neurological Disorders and Stroke (NINDS). June, 2017; https://www.ninds.nih.gov/disorders/chiari/detail_chiari.htm.
        2. Chiari Malformations. NORD. 2014; https://www.rarediseases.org/rare-disease-information/rare-diseases/byID/85/viewAbstract.
        3. Khoury C. Chiari malformations. UpToDate. Waltham, MA: UpToDate; June 28, 2017;
        4. Chiari malformations. Brain & Spine Foundation. June, 2015; https://www.brainandspine.org.uk/chiari-malformations.
        5. Chiari malformation. Mayo Clinic. September 29, 2016; https://www.mayoclinic.org/diseases-conditions/chiari-malformation/diagnosis-treatment/treatment/txc-20249732.
        6. Chiari Malformation. American Association of Neurological Surgeons. https://www.aans.org/Patients/Neurosurgical-Conditions-and-Treatments/Chiari-Malformation. Accessed 9/11/2017.

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