Can transverse sinus stenosis cause Benign Intracranial Hypertension (BIH)?

Transverse Sinus Stenosis Can Cause Benign Intracranial Hypertension

Transverse sinus stenosis can both cause and result from benign intracranial hypertension (BIH), creating a potential bidirectional relationship that affects morbidity and mortality through increased intracranial pressure and vision loss. 1, 2

The Relationship Between Transverse Sinus Stenosis and BIH

Evidence for Causation

• Transverse sinus stenosis creates pressure gradients across the venous system:
  • Studies demonstrate significant pressure gradients (average 20 mmHg) across stenotic segments 3
  • These pressure gradients impair cerebral venous drainage and CSF resorption
  • Stenting of stenotic segments immediately eliminates the pressure gradient and improves symptoms 3, 4

Evidence for Secondary Effect

• Transverse sinus stenosis may also be a consequence of elevated intracranial pressure:
  • Some patients with BIH show no change in their transverse sinus stenosis despite clinical improvement with medical therapy 5
  • This suggests the stenosis may sometimes be a result rather than cause of the increased pressure

Prevalence Considerations

• Transverse sinus stenosis is common in the general population:
  • 33% of normal population has unilateral transverse sinus stenosis/hypoplasia
  • 5% have bilateral transverse sinus stenosis 1
  • This high prevalence in asymptomatic individuals suggests stenosis alone is not sufficient to cause BIH

Diagnostic Approach

Imaging Techniques

• CT venography (CTV) or MR venography (MRV) are recommended initial imaging studies:
  • CTV demonstrates transverse sinus narrowing in BIH patients with statistical significance compared to controls 6
  • However, non-invasive imaging has limitations:
    • MRV sensitivity <0.5 in detecting significant stenosis with pressure gradient 1
    • Only 65% of patients with abnormalities on CTV/MRV demonstrated actual venous abnormalities on catheter venography 1

Definitive Diagnosis

• Catheter venography with manometry is the gold standard:
  • Measures actual pressure gradients across stenotic segments
  • A pressure gradient ≥8 mmHg is considered significant for treatment 1
  • Some patients with apparent stenosis on imaging show no pressure gradient on manometry 1

Treatment Implications

Venous Sinus Stenting

• Venous sinus stenting is effective for BIH with confirmed transverse sinus stenosis:
  • Immediately eliminates pressure gradients
  • Rapidly improves symptoms and abolishes papilledema 3
  • Success rates are high - 49 of 52 patients (94%) cured of all symptoms in one study 3
  • Follow-up periods of up to 9 years show sustained improvement 2

Patient Selection for Stenting

• Recommended for patients who:
  • Have failed medical therapy and weight loss
  • Demonstrate significant pressure gradient (≥8 mmHg) across stenosis 1, 2
  • Have threatened vision or intolerable symptoms

Clinical Pearls and Pitfalls

Important Considerations

• Not all transverse sinus stenosis requires treatment:
  • Stenosis without pressure gradient may be incidental
  • Medical management should be first-line therapy for BIH
  • Acetazolamide is the recommended first-line medication 2

Potential Complications

• Stent placement complications include:
  • Recurrent stenosis adjacent to previous stent (11.5% of cases) 3
  • Need for additional stenting in some cases
  • Potential for stent thrombosis

Monitoring

• Regular ophthalmologic evaluations are essential:
  • Monitor papilledema, visual acuity, and visual fields
  • Extended follow-up (>5 years) is recommended as late recurrences can occur 2

In conclusion, while transverse sinus stenosis is frequently associated with BIH, the relationship is complex. Definitive diagnosis requires demonstration of a pressure gradient, and treatment with stenting can be highly effective in selected patients who have failed medical management.