Atlantoaxial instability Subluxation

• Facts:
  Malformation seen in 10-15% of Down's syndrome patients
  
  Most commonly due to excessive laxity in the posterior transverse ligament, which causes increased mobility between the atlas (C1) and the axis (C2)
• History / PE:
  Behavioral changes
  Toricolis
  Urinary incontinence
  Vertebrobasiliar symptoms (dizziness, vertigo, diplopia)
  Upper motor neuron symptoms (leg spasticity, positive Babinski)
• Diagnosis:
  Lateral radiographs
• Treatment:
  Surgical fusion of C1 and C2
• Associated With:
  Down's syndrome