Superior Ophthalmic Vein Cannulation for Carotid Cavernous Fistula

The superior ophthalmic vein (SOV) approach for embolization of carotid-cavernous fistulas (CCFs) was first described over 25 years ago. CCFs are typically classified into 4 subtypes based on the etiology and nature of the lesion. Direct (Barrow type A) lesions involve an endothelial tear in the carotid artery itself, while indirect lesions (Barrow types B, C, or D) affect small branches of the internal or external carotid systems. Although 10% to 60% of CCFs may resolve spontaneously, and up to 30% of low-flow CCFs may improve with conservative management (carotid compression therapy), many progressive lesions require intervention.  Direct lesions are treatable with endoarterial procedures, whereas indirect lesions are best managed with transvenous embolization, with the ipsilateral inferior petrosal sinus (IPS) being the preferred access route. Initial reports characterized case series where the SOV route was used when traditional access through the IPS was unsuccessful. The SOV is typically accessed through the facial-angular venous system; however, vessel stenosis, hypoplasia, or tortuosity can sometimes prevent safe transvenous access via this route. Surgical cutdown for direct cannulation of the SOV is a safe and effective option when other endovascular approaches have been exhausted. Although advances in endovascular access techniques have reduced the need for this method, direct cannulation of the SOV via surgical cutdown remains a valuable technique in the surgical armamentarium. SOV cannulation for CCF is a critical but challenging procedure in the management of vascular abnormalities affecting the cavernous sinus. CCF is an abnormal communication between the carotid artery and the cavernous sinus, leading to increased venous pressure and subsequent orbital congestion, proptosis, conjunctival chemosis, and vision-threatening complications. Endovascular treatment has revolutionized CCF management, with transvenous embolization being the preferred approach. Although the femoral and jugular routes are standard access points, anatomical variations and venous thrombosis may necessitate alternative routes, among which SOV cannulation is a key option. The SOV is a vital orbital venous drainage pathway that connects the facial venous system to the cavernous sinus. However, its small caliber and anatomical variability make direct cannulation complex, requiring careful imaging guidance to ensure precise navigation and minimize complications. Despite these challenges, SOV access offers an invaluable route for embolization in cases where conventional venous access routes fail or are unavailable.  SOV cannulation is particularly indicated when the traditional transfemoral or transjugular approach is unsuccessful due to venous occlusion, thrombosis, or anatomic anomalies. Indirect dural CCFs with preferential drainage through the ophthalmic venous system also warrant SOV access for optimal embolization. Additionally, patients with severe proptosis and orbital venous congestion may require urgent intervention through SOV cannulation to prevent irreversible visual impairment. The procedure relies on detailed anatomical knowledge of the SOV, which originates from the angular vein near the medial canthus and courses posteriorly into the superior orbital fissure. Anatomical variations, tortuosity, and the close proximity to surrounding structures, such as the optic nerve and extraocular muscles, make precise catheterization crucial. The vein is usually accessed percutaneously via a medial canthal approach, with real-time imaging guidance from modalities such as ultrasound and fluoroscopy to confirm its patency and location. The procedure for SOV cannulation begins with meticulous preparation, including the administration of local or general anesthesia and the creation of a sterile field. Ultrasound is used to visualize the vein, ensuring accurate entry and minimizing the risk of complications. A micropuncture needle is introduced through a small medial canthal incision, and a guidewire is carefully threaded into the vein. Once access is secured, a microcatheter is advanced through the SOV into the cavernous sinus, guided by fluoroscopy and angiography. The final step involves embolization using coils, liquid embolic agents such as Onyx, or detachable balloons to occlude the fistulous communication. Postprocedural imaging is performed to confirm successful closure, and careful hemostasis is achieved to prevent venous leakage. Despite its advantages, SOV cannulation presents several technical challenges. Small, tortuous, or thrombosed veins can complicate access, often requiring advanced imaging techniques or alternative surgical exposure. The fragility of the SOV increases the risk of vein rupture and orbital hemorrhage, and improper needle placement may cause inadvertent arterial puncture or optic nerve injury. Incomplete embolization is another concern, as partial occlusion of the fistula can lead to symptom recurrence, necessitating repeat interventions. Infection and thrombophlebitis are additional risks, making postprocedural monitoring essential to ensure patient safety. Advancements in imaging, catheter technology, and minimally invasive techniques are continuously refining the approach to SOV cannulation for CCF treatment. Endoscopic-assisted visualization improves procedural accuracy, while robotic-assisted navigation enhances precision in catheter placement. The development of bioabsorbable embolic agents may reduce long-term complications, and artificial intelligence-assisted imaging analysis can optimize procedural planning, further improving success rates. These innovations are poised to make SOV cannulation safer and more effective, ultimately leading to better patient outcomes.