Atlantoaxial instability: causes

Common causes include :

1. Down syndrome
2. Rheumatoid Arthritis
3. Trauma
4. Ankylosing spondylitis

There are many potential causes of atlantoaxial instability. They are listed below with most common ones listed in bold:

• Rheumatoid Arthritis
• Achondroplasia
• Down Syndrome (occurs less frequently than atlantooccipital instability 10-20% vs 60%) (1)
• Grisel Syndrome
• Morquio Syndrome
• Congenital scoliosis
• Osteogenesis imperfecta
• Neurofibromatosis
• Larsen syndrome
• Spondyloepiphyseal dysplasia congenita
• Chondrodysplasia punctata
• Metatropic 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 abnormalities
• Os odontoideum
• Ossiculum terminale
• Third condyle
• Hypoplasia or absence of the dens
• Pseudoachondroplasia
• Cartilage-hair hyperplasia
• Ankylosing spondylitis
• Scott syndrome
• Infections of the head and neck
• Tumors
• Trauma
• Cerebral palsy
• Steroid therapy