It is important to recognize that the connection or articulation between the first and second cervical vertebra is the most mobile part of the vertebral column and has the least amount of inherent stability of the entire vertebral column. There are a number of developmental abnormalities that exist between the first and second cervical vertebral. They all produce some element of segmental instability. The consequence of this disorder may be temporary narrowing of the spinal canal with secondary compression of the neural elements. The odontoid process which projects upwards from the second cervical vertebra and the ligaments that connect the two vertebra are the only factors that limit motion.
Causes of Atlantoaxial Instability
Degeneration of the lower spine, with its consequent decreased motion, leads to more strain and movement in the upper cervical spine and may be one reason why atlantoaxial instability may become more clinically apparent as we age. Children may present with abnormal development of the odontoid process. There may be associated abnormalities of the posterior fossa of the brain, where the cerebellum is forced downwards into the spinal canal. Traumatic or rheumatoid arthritic destruction of the ligaments that secure the odontoid process in place can lead to atlantoaxial instability.
Signs and Symptoms of Atlantoaxial Instability
The most common symptoms in people with atlantoaxial instability is a changing, intermittent picture of abnormal neurological symptoms. There may be generalized weakness or episodes of falling. There may be associated incoordination if the cerebellum is involved. Occasionally, there is compromise of the vertebral artery which passes along the side of the vertebral column. This is more common as we age due to degenerative disease of the spine and blood vessels. Symptoms caused by insufficiency of the vertebral arteries include dizziness, seizures, mental retardation and syncope.
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Medical Content Last Updated on 07/12/2008
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