2020–2021 BCSC Basic and Clinical Science Course™
7 Oculofacial Plastic and Orbital Surgery
Part I: Orbit
Chapter 5: Orbital Neoplasms and Malformations
Vascular Tumors, Malformations, and Fistulas
Arteriovenous malformations (AVMs) are high-flow developmental anomalies that, like venous malformations, result from vascular dysgenesis. They are characterized by rapid arterial flow through the nidus into the draining venous circulation and often occur at choke anastomotic zones. Dilated corkscrew episcleral vessels and pulsatile proptosis may be present, and vascular steal or shunting from the orbit may produce ischemic changes. Noninvasive imaging supports the diagnosis, with CT revealing diffuse enhancement and MRI showing flow voids (Fig 5-5).
Figure 5-5 Arteriovenous malformation. A, Arteriovenous malformation in the right eye causing proptosis and arterialization of conjunctival vessels. B, T1-weighted, gadolinium-enhanced MRI shows enhancing superolateral nidus of lesion (arrow).C, Angiogram shows enlarged ophthalmic artery (arrow).D, Proptosis and arterialized vessels resolved after embolization and excision of nidus.
(Courtesy of Julian D. Perry, MD, and Alexander D. Blandford, MD.)
AVMs gradually enlarge as they recruit more arterial feeders. They often require treatment, which involves preoperative selective angiography with embolization followed by resection of the nidus. Failure to completely resect the nidus may allow recurrence; however, complete resection of the nidus may not be possible without significant morbidity. Exsanguinating arterial hemorrhage can occur with surgical intervention, especially in unsuspected lesions without preoperative embolization.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.