Can cerebral arteriovenous malformation (AVM) cause syncope?

Can Cerebral Arteriovenous Malformations Cause Syncope?

Yes, cerebral arteriovenous malformations (AVMs) can cause syncope, though it is not among their common presenting symptoms, with the mechanism likely related to seizure activity rather than direct hemodynamic effects.

Pathophysiology of Syncope in Cerebral AVMs

Cerebral AVMs are abnormal tangles of blood vessels characterized by direct arteriovenous connections without an intervening capillary bed 1. While they most commonly present with intracranial hemorrhage (>50% of cases), seizures (20-25%), headaches (15%), or focal neurological deficits (<5%) 2, syncope is a rare manifestation.

The mechanism of syncope in patients with cerebral AVMs appears to be primarily related to:

1. Epileptogenic activity: AVMs can trigger seizures that may lead to syncope through ictal or post-ictal mechanisms 3. This is supported by case reports where antiepileptic therapy resolved syncope episodes in patients with AVMs 3.

2. Vascular steal phenomena: Though uncommon, AVMs can occasionally cause focal neurological deficits by altering perfusion in surrounding brain tissue 2. In rare cases, this could theoretically affect areas involved in consciousness maintenance.

3. Hemorrhagic events: Acute bleeding from an AVM could potentially cause transient loss of consciousness, though this would typically present with additional neurological symptoms 2.

Diagnostic Considerations

When evaluating syncope in a patient with a known or suspected cerebral AVM:

• Comprehensive evaluation: According to the ACC/AHA/HRS guidelines on syncope, a detailed assessment is needed to differentiate between cardiovascular, neurogenic, and other causes 2.

• Imaging: MRI and cerebral angiography are essential for diagnosing and characterizing AVMs 1. MRI can identify the AVM and potential hemosiderin deposits suggesting prior hemorrhage, while angiography remains the gold standard for defining arterial and venous anatomy 2.

• EEG monitoring: May help identify seizure activity as the cause of syncope in AVM patients 3.

Management Implications

For patients with cerebral AVMs presenting with syncope:

• Antiepileptic therapy: If seizure activity is suspected as the mechanism, antiepileptic drugs should be considered 1, 3.

• AVM treatment decision: The management approach should weigh the natural history risk against treatment risks:

  • Annual risk of initial hemorrhage: 2-3% for unruptured AVMs 2
  • Mortality from first hemorrhage: 10-30% 2
  • Long-term disability among survivors: 10-20% 2

• Treatment options include:

  • Microsurgical resection (first-line for accessible Spetzler-Martin grade I-II AVMs)
  • Stereotactic radiosurgery (for small AVMs in eloquent areas)
  • Embolization (as part of a complete treatment plan)
  • Conservative management 1

Clinical Pitfalls

• Misattribution of syncope: Assuming cardiovascular causes without considering neurological etiologies like AVMs in patients with recurrent syncope.

• Incomplete evaluation: Failing to perform adequate neuroimaging in patients with atypical syncope features.

• Overlooking seizures: Not recognizing that syncope may be a manifestation of seizure activity in patients with AVMs.

• Partial treatment: Performing partial embolization without a complete obliteration plan, which may not reduce hemorrhage risk 1.

In summary, while syncope is not a common presentation of cerebral AVMs, it can occur primarily through epileptogenic mechanisms. When identified, management should focus on treating the underlying AVM according to established guidelines while addressing the specific mechanism of syncope.