Do Arteriovenous Malformations (AVMs) pose a risk for the development of aneurysms?

Association Between AVMs and Aneurysms

Yes, arteriovenous malformations (AVMs) are significantly associated with aneurysms, with approximately 7-23.5% of AVM patients harboring associated aneurysms, which substantially increases hemorrhage risk and mortality. 1, 2, 3

Epidemiology and Classification

The association between AVMs and aneurysms is well-documented in the medical literature:

• Approximately 7-17% of AVM patients have associated intracranial aneurysms according to the American Stroke Association guidelines 1
• More recent studies report even higher rates:
  • 23.5% of AVM patients had associated aneurysms in a large series of 366 patients 2
  • A systematic review of 10,093 AVMs found that 20.2% harbored associated aneurysms 4

Types of AVM-Associated Aneurysms

Associated aneurysms can be categorized based on their location relative to the AVM:

• Feeding artery aneurysms (flow-related)
• Intranidal aneurysms (within the AVM nidus)
• Unrelated aneurysms (typically on the circle of Willis)

Clinical Significance and Hemorrhage Risk

The presence of aneurysms significantly increases the hemorrhage risk in AVM patients:

• In patients with both AVMs and aneurysms who present with hemorrhage, the aneurysm is the bleeding source in approximately 49.2% of cases 4
• Flow-related aneurysms are the most common source of hemorrhage (78.5%) among ruptured AVM-associated aneurysms 4
• Female patients with AVMs and associated aneurysms have a significantly higher risk of hemorrhage (odds ratio 8.53) 3
• Location matters: infratentorial AVM-associated aneurysms have a higher rupture risk (60%) compared to supratentorial lesions (29%) 4

Management Considerations

Given the increased hemorrhage risk, management of AVM-associated aneurysms requires special consideration:

• The American Stroke Association recommends that associated aneurysms be treated during the same surgery if the operative field is adequate, or separately with endovascular or open surgical obliteration 1
• Treatment priority should be given to the aneurysm before AVM treatment to reduce the risk of hemorrhage during or immediately after AVM treatment 3
• Treatment options include:
  • Endovascular coiling
  • Surgical clipping
  • Embolization with liquid agents (NBCA or Onyx)

Treatment Outcomes

• Endovascular treatment of AVM-associated aneurysms has shown:
  • 80% cure rate
  • 8.7% complication rate
  • 78.8% good neurological outcome rate 4
• However, if the AVM is not completely obliterated, there is a significant recurrence rate (37.5%) of treated aneurysms after endovascular coiling 5

Pitfalls and Special Considerations

• New aneurysms may develop in patients with high-flow AVMs, necessitating long-term follow-up 3
• Aneurysms can rupture before, during, or immediately after AVM treatment 3
• Meticulous blood pressure control during aneurysm surgery is critical to avoid hemorrhage from the AVM 3
• In cases of incomplete AVM obliteration, treated aneurysms should be closely monitored due to the risk of recurrence 5

Conclusion

The evidence clearly demonstrates that AVMs pose a significant risk for the development of aneurysms. These associated aneurysms substantially increase the risk of hemorrhage and should be addressed as part of the comprehensive management strategy for AVM patients.