Fig. 9.

Split atlas: axial CT image through the atlas (C1 vertebra) of the craniocervical junction of a 9-year-old female struck by a car and sustaining severe chest injuries. The victim was intubated at the roadside. A developmental “split atlas” is present with anterior and posterior rachischisis defects present (arrows)—this is an important but rare mimic of fracture of the C1 vertebra. There were no acute fractures of the craniocervical junction in this patient