Fig. 6.

Posterior rachischisis: axial CT image through the atlas (C1 vertebra) of the craniocervical junction of a road traffic accident victim (pedestrian versus car with “bullseye” impact of the victim’s head against the windscreen of the car) demonstrating a developmental posterior rachischisis (arrow) which should not be confused with an acute fracture. The well-corticated margin of the cleft should alert one to the developmental nature of the anomaly in addition to the typical location and unity of the defect compared to a traumatic aetiology