The occipital artery: a microanatomical study.

Objective: We performed a systematic microanatomical study of the occipital artery (OA) and its branches to describe the course, diameter, and branches of this vessel as well as the presence and pattern of anastomotic channels between the OA and the vertebral artery.

Methods: Twelve occipital arteries (6 adult cadaveric heads injected with colored latex) were studied using the surgical microscope. Particular attention was given to the course and branching pattern of the artery as well as the presence and type of anastomotic channels between the occipital artery and vertebral artery.

Results: Based upon anatomical considerations, the course of the occipital artery was divided into three segments. The first, or digastric segment, extends from the origin to the exit off the occipital groove of the mastoid process. The second segment, or suboccipital, extends from the occipital groove to the superior nuchal line. The third, or terminal segment, corresponds to the subgaleal segment just above the superior nuchal line up to the vertex. Two main descending branches of the second segment or suboccipital were identified. The superficial descending branch (SDB) runs between the splenium capitis and semispinalis capitis while the deep descending branch (DDB) enters the suboccipital triangle. Anastomotic vessels between one of these two descending branches and branches of the vertebral artery were found in 11 out of the 12 OAs dissected (91%).

Conclusion: Detailed knowledge of the OA anatomy is helpful in choosing this vessel as a donor for extra-intracranial bypasses. More importantly, knowledge and understanding of the type and pattern of anastomoses between the OA and the vertebral artery are critical to avoid disastrous complications (i.e., posterior circulation stroke) during embolization of vascular or neoplastic processes fed by distal OA branches.