Pediatric Atlanto Occipital Instability

  • Etiology: ligamentous laxity of cruciform ligament causes occiput-C1 + C1-C2 instability in Trisomy 21
  • Imaging: Predental space (atlanto-dental interval) should be < 4 mm — Occiput-C1 instability – posterior translation of opisthion on extension, see incongruence of Wackenheim’s line — C1-C2 instability – see widening of atlanto-dens interval on flexion, atlanto-dens interval > 5 mm on any lateral c-spine is abnormal, if there is any motion at atlanto-dens interval between flexion + extension it is abnormal
  • Clinical: can be exacerbated after minor trauma, can cause chronic cord injury with cord narrowing

Radiology Cases of Atlanto Occipital Instability

Radiograph of atlanto occipital instability
Lateral radiograph of the cervical spine in flexion (left) shows a normal atlanto dens interval and normal relationship of the occipital condyles to the lateral masses of C1 while on extension (right) there is posterior translation of the occipital condyles in relation to the lateral masses of C1.