Atlantoaxial Instability (AAI)


Etiology

Rheumatologic Disease

Other

  • Cartilage-Hair Hyperplasia
  • Cerebral Palsy (see Cerebral Palsy)
  • Chondrodysplasia Punctata
  • Congenital Scoliosis
  • Corticosteroid Therapy (see Corticosteroids)
  • Down Syndrome (see Down Syndrome)
    • Physiology: tranverse ligament laxity
  • Dwarfism (see xxxx)
  • Head and Neck Infection (Especially Pharyngeal Infection) (see Deep Neck Infection)
    • Physiology: transverse ligament inflammation, predisposing to atlantoaxial subluxation
  • Hypoplasia or Absence of Dens
  • Kniest Syndrome
  • Larsen Syndrome
  • Metatropic Dysplasia
  • Morquio Syndrome
  • Mucopolysaccharidoses
  • Neurofibromatosis (see Neurofibromatosis)
  • Odontoid Abnormalities
  • Os Odontoideum
  • Ossiculum Terminale
  • Osteogenesis Imperfecta
  • Pseudoachondroplasia
  • Scott Syndrome
  • Spondyloepiphyseal Dysplasia Congenita
  • Third Condyle
  • Trauma to Neck
  • Tumors
    • Physiology: may cause fracture of body of the axis

Physiology

Mechanisms of Atlantoaxial Instability

  • Bony Odontoid Abnormalities: may be due to either abnormal odontoid development/ossification or fracture
  • Fracture of Body of the Axis: may occur with tumors
  • Transverse Ligament Laxity/Inflammation: may occur with RA and infections

Clinical Manifestations

Neurologic Manifestations


References