Atlantoaxial Instability Explained

Atlantoaxial instability is extra movement between the first two vertebrae of the neck. This site's Down syndrome guide calls it the safety item that matters most before a therapy involving head and neck positioning. The AAP covers it in its 2022 clinical report on health supervision for children and adolescents with Down syndrome, the main source for this explainer, along with the AAP's parent page on the condition.

What atlantoaxial instability is

The atlas (C1) and the axis (C2) are the top two bones of the spine, just below the skull. Atlantoaxial instability means there is more movement than usual between them. According to the AAP's parent page, written by the lead author of the 2022 report, in children with Down syndrome it is caused by a combination of low muscle tone, loose ligaments, and bony changes, and the spinal cord can be pressed by the bones of the neck, causing nerve damage. The same page notes that symptoms can occur at any time and that "there is no test or x-ray that can tell who is at risk."

How common it is

The 2022 report's table of conditions in Down syndrome lists symptomatic atlantoaxial instability at 1% to 2%, and the report describes children with Down syndrome as at "slightly increased risk of symptomatic atlantoaxial subluxation." The report does not give a separate figure for children who show extra movement on an x-ray but have no symptoms.

Symptoms the AAP tells parents to watch for

The 2022 report says parents should contact their physician about new onset of any of these: a change in gait or in use of the arms or hands; a change in bowel or bladder function; neck pain or a stiff neck; a head tilt or torticollis; a change in how the child positions their head; a change in general function; or weakness. The AAP's parent page adds becoming fatigued more easily and a decrease in activity level.

The report also says that any child with significant neck pain, radicular pain (pain that travels along a nerve), weakness, spasticity or a change in muscle tone, difficulty walking, overactive reflexes, a change in bowel or bladder function, or other signs of spinal cord compression must have a neck x-ray in the neutral position. If that x-ray shows significant abnormalities, the child should be referred as quickly as possible to a pediatric neurosurgeon or pediatric orthopedic surgeon with expertise in atlantoaxial instability.

How the screening guidance changed

Children with Down syndrome were once routinely screened with neck x-rays. In 2011, the AAP changed its guidance so that x-rays are taken only when a child has symptoms suggesting a problem in the cervical spine. The 2011 report gave three reasons, and the 2022 report repeats them: plain x-rays do not predict well which children will develop spine problems, a normal x-ray does not guarantee that a child will not develop problems later, and children under 3 do not have enough bone development for an accurate x-ray. The 2022 report states: "Current evidence does not support performing routine screening radiographs for assessment of potential atlantoaxial instability in asymptomatic children." Instead, the pediatrician takes a careful history and does a physical exam, watching for signs of spinal cord compression, at every well-child visit.

A 2020 review by pediatric neurosurgeons at Children's Hospital Colorado looked at one center's experience with the 2011 guidance. It found that even when x-rays were limited to children with signs or symptoms, the vast majority were negative, and it concluded that routine screening may not be sufficiently predictive of which children are at risk. It is a single-center review, not a trial.

What the guidance says about activities

The 2022 report's activity advice applies to all children with Down syndrome, not only those with symptoms. Pediatricians are told to advise that contact sports, such as football, soccer, and gymnastics, place children at risk for spinal cord injury, and that trampolines should be avoided by all children, with or without Down syndrome, unless part of a structured training program with appropriate supervision and safety measures. The report also notes that Special Olympics requires documentation of a physical examination for all athletes, and it asks pediatricians to discuss precautions that protect the neck during any anesthesia, surgery, or x-ray procedure.

What it means for your child

The AAP report does not mention DMI or any other therapy approach, and its neck-positioning precautions are written for anesthesia, surgery, and x-rays, not for therapy sessions. This site applies the same caution to hands-on therapy that involves head and neck positioning. The Down syndrome guide advises telling your DMI therapist about the diagnosis before the first session and asking directly how they handle cervical spine precautions. The global developmental delay and hypotonia guides note that cervical spine precautions apply if your child has Down syndrome or another condition associated with atlantoaxial instability.

What it does not establish

The 1% to 2% figure is the share of children with Down syndrome who develop symptoms. It does not tell you any one child's risk, and the AAP's parent page says no test can. The report is clinical guidance for pediatricians, not an outcome study, and the AAP itself says that "a rigorous, evidence-based review of screening and treatment of atlantoaxial instability" is needed. Nothing here is evidence about whether DMI works. It is a safety precaution, not an effectiveness claim. The evidence on DMI is covered on the research page.

What to ask

• Does the therapist ask about Down syndrome and any neck symptoms before the first session?
• How do you protect the neck during positioning with a child who has Down syndrome?
• Which symptoms would make you stop a session and send us to our child's doctor?
• At well-child visits, is the pediatrician checking for signs of spinal cord compression? The AAP recommends a history and physical exam at every visit.

Where it appears on this site

The Down syndrome guide covers atlantoaxial instability in its section on what every parent should know before hands-on therapy. The conditions index lists it as a reason it matters to know your child's diagnosis before any hands-on therapy, and the global developmental delay and hypotonia guides repeat the cervical spine precaution.

Sources

• Bull MJ, Trotter T, Santoro SL, Christensen C, Grout RW; Council on Genetics. Health Supervision for Children and Adolescents With Down Syndrome. Pediatrics. 2022;149(5):e2022057010. AAP Pediatrics
• Bull MJ; Committee on Genetics. Health Supervision for Children With Down Syndrome. Pediatrics. 2011;128(2):393-406. AAP Pediatrics
• Hengartner AC, Whelan R, Maj R, Wolter-Warmerdam K, Hickey F, Hankinson TC. Evaluation of 2011 AAP cervical spine screening guidelines for children with Down Syndrome. Childs Nervous System. 2020;36(11):2609-2614. PubMed
• Bull MJ. Atlantoaxial Instability in Children with Down Syndrome. HealthyChildren.org, American Academy of Pediatrics. HealthyChildren.org