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Background: Variations in bone are common. Atlas vertebrae are especially subject to variation and are of clinical importance because of its close relation to vertebral artery. Bony spur can arise from the posterior margin for the groove of vertebral artery and form bridges known as ponticles. The bridges can be posterior, lateral or posterolateral. If the bridge is complete it is known as arcuate foramen. These variations can predispose to vertebrobasilar insufficiency.