E3309. Persistent Carotid-Vertebrobasilar Anastomoses and Their Classic Appearance
  1. Abdurrahman Roussi; Wake Forest School of Medicine
  2. Kyle Atcheson; Atrium Health Wake Forest Baptist Hospital; Wake Forest School of Medicine
  3. Kevin Hiatt; Atrium Health Wake Forest Baptist Hospital; Wake Forest School of Medicine
Persistent carotid-vertebrobasilar (CVB) anastomoses are a rare form of communication between the anterior and posterior circulations due to abnormal embryological development. Around week 4, CVB anastomoses form and persist for about 1 week. They begin to regress as the posterior communicating artery and vertebral arteries form. First to regress is the otic (acoustic) artery, followed by the hypoglossal, trigeminal, and proatlantal arteries. The proatlantal artery consists of a type I and a type II variant leading to a total of five different variants of CVB anastomoses.

Educational Goals / Teaching Points
By the end of this exhibit, the participant should be able to demonstrate an understanding of the embryology of CVB anastomoses, identify the five types of persistent CVB anastomoses, and demonstrate an understanding of the clinical implications of CVB anastomoses.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Persistent CVB anastomoses are rare incidental findings encountered on CTA or MRA. While mostly benign, they are important for radiologists to identify. They are associated with various neurological diseases including aneurysm, vertebrobasilar insufficiency, and Moya-Moya disease. They may also complicate endovascular interventions if not properly identified. As such, confidently identifying these anastomoses is essential for a radiologist to ensure appropriate treatment. CVB anastomoses are named according to the corresponding cranial nerve that courses nearby. The proatlantal artery is an exception to that rule and is named relative to its position to the atlas (C1). All CVB anastomoses arise from the internal carotid artery, with the exception of type II proatlantal artery, which arises from the external carotid artery. The trigeminal artery is the most common anastomosis, and the otic (acoustic) artery is the least common.

Persistent CVB anastomoses are a rare, mostly benign, and typically incidental finding. Their significance emerges in the acute setting or when patients require endovascular interventions. Therefore, radiologists should be aware of the different types of CVB anastomoses and their clinical implications.