Can a Cognard type 3 (Dural Arteriovenous Fistula) DAVF (Dural Arteriovenous Fistula) cause a subdural hemorrhage?

Cognard Type 3 Dural Arteriovenous Fistulas and Subdural Hemorrhage

Yes, Cognard type 3 dural arteriovenous fistulas (DAVFs) can cause subdural hemorrhage, as they have cortical venous drainage which significantly increases hemorrhagic risk. 1, 2, 3

Understanding Cognard Type 3 DAVFs

Cognard type 3 DAVFs are characterized by:

• Direct cortical venous drainage without venous ectasia
• Absence of dural sinus drainage
• Higher risk of hemorrhagic complications compared to lower Cognard grades

Hemorrhagic Risk Profile

DAVFs with cortical venous reflux (including Cognard type 3) present a significant risk of hemorrhage 1. While most DAVF-related hemorrhages are intracerebral, they can also manifest as:

• Subarachnoid hemorrhage (most common)
• Intracerebral hemorrhage
• Subdural hemorrhage (rare but documented)

Evidence for Subdural Hemorrhage in DAVFs

Several case reports have documented subdural hemorrhage as a complication of DAVFs:

• A 69-year-old patient presented with spontaneous right-sided symptomatic chronic subdural hematoma that was later found to be caused by an occipital tentorial DAVF Cognard type 3 1
• Another case report described a rare presentation of a patient with spontaneous subdural hemorrhage that was diagnosed as a DAVF after cerebral angiography 2
• A review of cases found that isolated subdural hematoma is a rare but recognized complication of DAVFs 3

Pathophysiological Mechanism

The mechanism for subdural hemorrhage in DAVFs likely involves:

1. High pressure in the cortical veins due to arterial blood reflux
2. Rupture of fragile cortical veins that traverse the subdural space
3. Direct bleeding into the subdural compartment rather than into brain parenchyma

Diagnostic Approach for Suspected DAVF

When a patient presents with spontaneous subdural hemorrhage without trauma history:

• Initial CT or MRI to identify the hemorrhage
• CT angiography to look for dilated convoluted vessels and enlarged feeding arteries
• Cerebral angiography (gold standard) to definitively diagnose and classify the DAVF 4

Treatment Considerations

For Cognard type 3 DAVFs with subdural hemorrhage:

• Endovascular embolization is considered first-line therapy 5
  • Transarterial approach for accessible feeding arteries
  • Transvenous approach when arterial access is limited
• Surgical intervention may be necessary when:
  • Endovascular access is limited
  • Previous embolization failed to obliterate the fistula
  • The DAVF has complex angioarchitecture 5, 1

Clinical Implications

• Careful preoperative investigation is needed for relatively young patients presenting with idiopathic or atypical subdural hematoma 3
• Even "benign" types of DAVFs without cortical venous drainage might be complicated with subdural hemorrhage 3
• Long-term monitoring is necessary after treatment to detect recurrence 5

Conclusion

The presence of cortical venous drainage in Cognard type 3 DAVFs significantly increases the risk of intracranial hemorrhage, including rare but documented cases of subdural hemorrhage. This underscores the importance of thorough vascular imaging in cases of spontaneous subdural hemorrhage without clear traumatic etiology.