Figure 10 The carotid artery is immediately anterior to the C1 lateral masses. The vertebral artery takes two 90 degree turns at the level of C1. The carotid artery is immediately anterior to the C1 lateral masses. The vertebral artery takes two 90 degree turns at the level of C1. The first involves posterior turn just cephalad of the transverse foramina of C2. The second turn involves a turn toward the midline at the level of the posterior arch of C1. Level: Structures: Other Structures: Pathology: Procedure: View: Entire occipitocervical junction Neural: C1 Dura Vascular: Carotid artery and vertebral arteries None Normal None Composite (3/4), Front, Lateral, Caudal