Atlantooccipital Dislocation

KEY FACTS

Terminology

• Disruption of stabilizing ligaments between occiput and C1

Imaging

• Widened prevertebral soft tissues (nonspecific)

• Condylar sum > 4.2 mm has 100% sensitivity, 69% specificity, and 76% accuracy

• Increased basion-dens interval (BDI) distance > 8.5 mm (CT in adults)

• Widened unilateral atlantooccipital interval > 2 mm

  • Widened, fluid-filled facet joints between condyles and C1

• STIR/T2WI MR best show ligamentous injury

Top Differential Diagnoses

• Occipital condyle fracture

• C1 Jefferson fracture

• Odontoid fracture

• Rheumatoid arthritis, adult

Pathology

• High-speed motor vehicle accident

• Associated injuries

  • Brainstem and cranial nerve injury

  • Fractures of occipital condyles, C1 and C2

Clinical Issues

• < 1% of acute cervical spine injuries

• Often immediately fatal; however, may have good outcome with recognition and fixation

Diagnostic Checklist

• No imaging sign 100% sensitive

• Condylar sum > 4.2 mm most sensitive CT sign of atlantooccipital dislocation

• Powers ratio not recommended (has low sensitivity and specificity)

• Detection of subarachnoid hemorrhage at craniocervical junction should direct search for atlantooccipital injuries

TERMINOLOGY