Figure 3.

Intraoperative angiography performed before (A) and after (B) microsurgical decompression of the left vertebral artery at the C4-5 level with the patient's head turned to the left. Prior to decompression (A), there is obstruction of flow through left vertebral artery at the caudal aspect of the C4 foramen transversarium (circle). Following decompression (B), including resection of the C4-5 osteophyte, partial C4-5 discectomy, and removal of a fibrous band overlying the vertebral artery, the luminal diameter of the vertebral artery at the C4-5 level is significantly improved with the neck in the left rotated position.