Is there a risk of Onyx (ethylene-vinyl alcohol copolymer) migration into the vein of Labbe during embolization of a fistula located at the 12 o'clock position of the left transverse sigmoid sinus junction?

Risk of Onyx Migration into the Vein of Labbe During Dural Arteriovenous Fistula Embolization

Yes, there is a significant risk of Onyx migration into the vein of Labbe during embolization of a fistula at the left transverse sigmoid sinus junction, especially given the anatomical relationship you've described. This risk requires careful consideration during procedural planning and execution.

Anatomical Risk Assessment

• The fistula is located at the 12 o'clock position of the left transverse sigmoid sinus junction
• The vein of Labbe inserts at the 2-3 o'clock position of the same junction
• Cortical venous reflux from the fistula merges with the vein of Labbe before insertion

This configuration creates a high-risk scenario for inadvertent Onyx migration for several reasons:

• Proximity: The close anatomical relationship between the fistula and the vein of Labbe insertion point (approximately 2-3 hours apart on the clock face)
• Venous drainage pattern: The described cortical venous reflux that merges with the vein of Labbe creates a direct pathway for potential Onyx migration
• Flow dynamics: During embolization, pressure changes can redirect embolic material along paths of least resistance

Technical Considerations

When performing embolization with Onyx for this type of fistula:

1. Visualization requirements:

   • Biplanar fluoroscopy is essential to adequately visualize Onyx migration in multiple planes 1
   • Single-plane fluoroscopy has been associated with inadvertent venous migration of Onyx with catastrophic consequences 1

2. Injection technique:

   • The "plug-and-push" technique should be used with extreme caution
   • Slow, controlled injection with frequent pauses to assess for unexpected Onyx migration
   • Be prepared to pause injection if any concerning patterns of flow are observed 2

3. Blood pressure management:

   • Consider induced hypotension during critical phases of Onyx injection
   • Hypotension slows flow through the fistula and provides more controlled deposition of embolic material 3

Risk Mitigation Strategies

To minimize the risk of Onyx migration into the vein of Labbe:

• Pre-procedural planning:

  • Detailed angiographic assessment of all feeding arteries and draining veins
  • Consider 3D rotational angiography to better understand the complex anatomy
  • Map the exact relationship between the fistula, the vein of Labbe, and the transverse sinus

• Procedural approaches:

  • Consider protective coiling of the vein of Labbe prior to Onyx injection if technically feasible
  • Use staged embolization with smaller volumes of Onyx per session
  • Consider alternative embolic agents if the risk is deemed too high

• Monitoring during injection:

  • Continuous assessment of Onyx cast formation
  • Immediate cessation of injection if any unexpected Onyx migration is observed
  • Be vigilant for any Onyx patterns that suggest it may be approaching the vein of Labbe

Potential Complications

If Onyx migrates into the vein of Labbe, potential complications include:

• Venous infarction of the temporal lobe
• Hemorrhagic conversion of venous infarct 1
• Permanent neurological deficits
• Potential mortality in severe cases

Conclusion

The anatomical configuration you've described presents a significant risk for Onyx migration into the vein of Labbe. While embolization can be performed, it requires meticulous technique, appropriate visualization equipment (biplanar fluoroscopy), and readiness to abort the procedure if concerning patterns of Onyx migration are observed. The risk is heightened by the described cortical venous reflux that directly connects with the vein of Labbe.