Atlantoaxial instability: causes

Common causes include :Down syndromeRheumatoid ArthritisTraumaAnkylosing spondylitisThere are many potential causes of atlantoaxial instability. They are listed below with most common ones listed in bold:Rheumatoid ArthritisAchondroplasiaDown Syndrome (occurs less frequently than atlantooccipital instability 10-20% vs 60%) (1)Grisel SyndromeMorquio SyndromeCongenital scoliosisOsteogenesis imperfectaNeurofibromatosisLarsen syndromeSpondyloepiphyseal dysplasia congenitaChondrodysplasia punctataMetatropic dysplasia (a rare syndrome that can present with AAI)Kniest syndrome (also can present with AAI; a workup must be performed prior to any operative interventions)Odontoid abnormalitiesOs odontoideumOssiculum terminaleThird condyleHypoplasia or absence of the densPseudoachondroplasiaCartilage-hair hyperplasiaAnkylosing spondylitisScott syndromeInfections of the head and neckTumorsTraumaCerebral palsySteroid therapy