Exploiting the Non-dilated Superior Ophthalmic Vein for Embolization of Carotid-Cavernous Fistula: Systematic Review on Presentation, Clinical and Angiographic Outcomes

Technical Summary: Exploiting the Non-dilated Superior Ophthalmic Vein for Embolization of Carotid-Cavernous Fistula

Problem Statement
Carotid-cavernous fistulas (CCFs), particularly indirect types, are typically treated via transvenous embolization, with the inferior petrosal sinus (IPS) serving as the preferred initial route. However, the IPS is inaccessible in approximately 31% of cases due to hypoplasia, thrombosis, or complex plexiform architecture. In such scenarios, the superior ophthalmic vein (SOV) serves as a critical alternative anterior transvenous route. Traditionally, endovascular surgeons have favored SOV access only when the vein is visibly dilated, arterialized, and clearly opacified on imaging. Consequently, a non-dilated, stenosed, thrombosed, or angiographically occult SOV is often viewed as an absolute barrier to treatment, potentially leaving patients with progressive ocular morbidity and dangerous intracranial venous reflux with limited therapeutic options. The central clinical question addressed is whether unfavorable SOV morphology precludes successful fistula access or if these veins remain surgically identifiable and catheterizable.

Methodology
The authors conducted a PRISMA 2020-compliant systematic review of literature published up to April 2026. The search encompassed MEDLINE, CINAHL, PsycINFO, EMBASE, the Cochrane Library, and Scopus.

• Inclusion Criteria: Studies reporting original clinical data on CCF or cavernous sinus dural arteriovenous fistulas treated or attempted via direct puncture, surgical exposure, cutdown, or cannulation of a non-dilated SOV (defined as normal caliber, small, stenosed, narrowed, thrombosed, or occluded).
• Exclusion Criteria: Cases where the SOV was merely a drainage pathway rather than the access site, cases involving dilated SOVs, or cases where access was obtained via other routes (e.g., IPS, facial vein) even if the SOV was occluded.
• Data Synthesis: The review included five published reports contributing eight eligible access attempts. An institutional illustrative case (an 82-year-old woman with a Barrow type D indirect CCF and non-dilated SOV) was presented separately to demonstrate the technique but was excluded from the quantitative synthesis.
• Quality Assessment: Methodological quality was assessed using Joanna Briggs Institute (JBI) tools, acknowledging the inherent limitations of case reports and small series.

Key Contributions and Results
The review identified eight access attempts in non-dilated SOVs across five reports. The cohort consisted entirely of indirect CCFs (100%), with 87.5% of cases having prior failed or infeasible conventional access attempts (e.g., failed IPS, facial vein, or transarterial routes).

• SOV Status: In 62.5% (5/8) of cases, the SOV was thrombosed or occluded. In the remaining 37.5% (3/8), the vein was progressively stenosed or non-dilated.
• Technical Success: Direct SOV access was successful in 6/8 attempts (75%). The two failures were attributed to severe stenosis/atresia preventing cannulation.
• Technique: All successful attempts involved direct surgical exposure (e.g., frontotemporal craniotomy with orbital wall deroofing, anterior orbitotomy, or upper-eyelid incision) often coordinated with oculoplastic surgeons. Cannulation techniques varied, including the use of 18G/20G angiocatheters, microguidewires, and balloon-tipped catheters. In cases of thrombosis, catheters were advanced through the thrombosed segment.
• Embolization Strategy: Coils were the primary embolic agent, used in 83.3% (5/6) of successful cases. Coil-only embolization was performed in 66.7% (4/6) of successful cases.
• Outcomes:
  • Angiographic: Immediate complete angiographic cure (fistula obliteration) was achieved in 100% (6/6) of technically successful cases.
  • Clinical: 100% of successful cases demonstrated clinical improvement, including resolution of proptosis, chemosis, and diplopia. Visual acuity improved in all 5 cases with extractable data.
  • Safety: No access-related complications, periprocedural strokes, or recurrences were reported among the successful cases with available follow-up (mean 9.8 months).
• Illustrative Case: The institutional case demonstrated successful coil embolization through a surgically exposed, non-dilated SOV (2.13 mm diameter) after failed IPS access, resulting in complete shunt obliteration and symptom resolution at 3-month follow-up.

Significance and Claims
The paper posits that a non-dilated, stenosed, or even thrombosed SOV should not be considered an absolute contraindication for transvenous embolization. The authors claim that:

1. Feasibility: Unfavorable angiographic morphology does not necessarily equate to anatomical inaccessibility. These veins can remain surgically identifiable and catheterizable.
2. Salvage Strategy: Direct SOV access should be considered a viable salvage strategy when conventional transvenous routes (like the IPS) are unavailable or have failed.
3. Multidisciplinary Requirement: Successful execution relies on a specific technical framework: planned orbital exposure with an oculoplastic surgeon, secure venous control (e.g., clipping, sutures), fluoroscopic navigation, and a defined hemostatic exit strategy.
4. Cautious Optimism: The authors emphasize that while the results are promising, the evidence base is small and derived from highly selected cases. They do not advocate for this as a first-line treatment but rather as a critical option for carefully selected patients facing progressive morbidity due to inaccessible standard routes. The study highlights that the "non-dilated" status is a relative, not absolute, barrier to treatment.