Term of the Week: Atlantoaxial Instability

Atlantoaxial instability (at-lan-toe-ax-ee-ul instability), often referred to as AAI, is a condition affecting the two bones at the top of the spinal cord. About 15% of people with Down syndrome will have AAI diagnosed on an x-ray. Because people with Down syndrome can have somewhat stretchier ligaments, the two bones at the top of the neck (called C1 and C2) may be prone to excessive movement. Often this condition causes no problems, but very rarely it can affect the underlying nerves leading to serious neurological problems.

There are two forms of atlantoaxial instability: asymptomatic AAI and symptomatic AAI. Asymptomatic AAI means that the condition is not causing any symptoms in the person that has it. Symptomatic AAI occurs when the excessive movement of the vertebrae cause neurological problems which can range from mild to severe. People with symptomatic AAI should see a neurologist immediately to assess their symptoms and come up with a plan to manage the disorder.

Most people with Down syndrome do not have AAI in either form. Approximately 10-20% of people with Down syndrome will have asymptomatic AAI and will not require any medical treatment. Only 1-2% of people with Down syndrome will have symptomatic AAI. The treatments for symptomatic AAI include a soft collar or neck brace, muscle relaxants and sometimes surgery.

Read more about atlantoaxial instability here.