Pseudonotch of the atlas vertebra simulating fracture with computed tomographic diagnosis. A case report.

Pseudonotch of the atlas represents a normal variation of the atlas related to a notched protuberance of the medial surface of its lateral masses. A case is presented in which cervical spine roentgenography revealed a prominent pseudonotch that mimicked a fracture of the lateral masses of the atlas. Minimal rotation of C-1 on C-2 was present without apophyseal joint subluxation. Computed tomography imaging provided an accurate diagnosis.