Can cerebral venous sinus thrombosis cause syncope?

Cerebral Venous Sinus Thrombosis as a Cause of Syncope

Cerebral venous sinus thrombosis (CVST) can cause syncope, particularly through mechanisms involving increased intracranial pressure that leads to transient cerebral hypoperfusion. While syncope is not a common presenting symptom of CVST, it can occur in specific circumstances.

Pathophysiological Mechanisms

The relationship between CVST and syncope involves several potential mechanisms:

1. Increased intracranial pressure (ICP):

   • CVST causes venous outflow obstruction leading to elevated ICP
   • Paroxysmal elevations in ICP can temporarily reduce cerebral perfusion pressure
   • When cerebral perfusion falls below critical thresholds (approximately 20% reduction in cerebral oxygen delivery), syncope can occur 1

2. Venous congestion:

   • Thrombosis of major venous sinuses causes venous congestion and cerebral edema
   • This can lead to decreased cerebral blood flow and subsequent syncope

3. Anatomical considerations:

   • Patients with hypoplastic contralateral venous sinuses are at higher risk of developing elevated ICP when the dominant sinus is thrombosed 2
   • This anatomical variation reduces compensatory venous drainage capacity

Clinical Presentation and Diagnosis

When evaluating syncope potentially related to CVST:

• Associated symptoms that suggest CVST rather than other causes of syncope:

  • Headache (often severe and persistent)
  • Visual disturbances
  • Focal neurological deficits
  • Seizures
  • Altered mental status

• Diagnostic approach:

  • MRI with MR venography (MRV) is the preferred imaging modality 3
  • CT venography (CTV) is an alternative when MRI is contraindicated
  • Direct cerebral venography may be performed during endovascular procedures
  • Cerebral angiography is reserved for inconclusive cases or when endovascular treatment is being considered 3

Differentiation from Other Causes of Syncope

According to European Heart Journal guidelines, syncope is categorized into:

1. Neurally-mediated (reflex) syncope
2. Orthostatic hypotension
3. Cardiac arrhythmias
4. Structural cardiac disease
5. Cerebrovascular causes (including vascular steal syndromes) 3

CVST falls under cerebrovascular causes but is not explicitly listed in standard syncope classifications. The European Heart Journal guidelines note that "neurological referral is warranted when syncope may be due to a cerebrovascular cause" 3.

Case Evidence

The connection between CVST and syncope is supported by case reports:

• A documented case describes "recurrent syncope due to refractory cerebral venous sinus thrombosis and transient elevations of intracranial pressure" 1
• This demonstrates that intermittent elevations in ICP can lead to syncopal episodes in patients with venous sinus thrombosis

Management Implications

When CVST is identified as the cause of syncope:

1. Anticoagulation therapy is the first-line treatment for CVST 4
2. Management of increased ICP is crucial
3. Treatment of underlying causes (prothrombotic states, infection, etc.)
4. Consideration of more aggressive therapies in refractory cases:
   • Endovascular thrombolysis
   • Thrombectomy
   • Decompressive craniectomy 5, 6

Clinical Pearls and Pitfalls

• Pitfall: Failing to consider CVST in patients with atypical syncope, especially when accompanied by headache or neurological symptoms
• Pitfall: Relying solely on non-contrast CT, which may miss CVST
• Pearl: Consider CVST particularly in young adults and women with risk factors (oral contraceptives, pregnancy, thrombophilias)
• Pearl: Recent COVID-19 infection or vaccination has emerged as a potential risk factor for CVST 5

In conclusion, while CVST is not among the common causes of syncope, it should be considered in the differential diagnosis when syncope is accompanied by headache, neurological deficits, or occurs in patients with risk factors for venous thrombosis. Prompt diagnosis and treatment are essential to prevent potentially serious outcomes.