What is cerebral venous sinus thrombosis?

Cerebral Venous Sinus Thrombosis (CVST)

Cerebral venous sinus thrombosis (CVST) is a rare form of stroke (0.5-1% of all strokes) caused by thrombosis in cerebral veins or dural sinuses, leading to impaired venous drainage and increased intracranial pressure, predominantly affecting young individuals under 50 years of age. 1, 2

Pathophysiology

• CVST occurs when blood clots form in cerebral veins or dural sinuses, causing venous congestion, increased intracranial pressure, and potential brain tissue damage 2
• Unlike arterial strokes, venous infarcts often cross arterial boundaries and are frequently hemorrhagic 2
• Venous occlusion leads to localized edema and potential hemorrhagic transformation due to increased venous pressure 3

Clinical Presentation

• Headache is the most common presenting symptom, typically diffuse and progressively worsening over days to weeks 2
• Presentation varies with 37% presenting acutely, 56% subacutely, and 7% chronically 2
• Seizures occur in approximately 40% of CVST patients, significantly higher than in arterial stroke 2
• Symptoms correlate with affected venous structures:
  • Superior sagittal sinus thrombosis: frontal, parietal, and occipital lobe symptoms 3
  • Lateral (transverse) and sigmoid sinus thrombosis: temporal lobe manifestations 3
  • Deep venous system thrombosis (vein of Galen or straight sinus): thalamic involvement, altered consciousness without focal signs 3, 2

Risk Factors

• Prothrombotic conditions: inherited thrombophilias (protein C/S deficiency, antithrombin III deficiency, factor V Leiden) 2
• Female-specific factors: oral contraceptive use, pregnancy, postpartum period 2
• Other factors: malignancy, inflammatory conditions, dehydration 2

Diagnosis

• MRI with MR venography is the preferred diagnostic modality, showing both venous occlusion and parenchymal changes 1, 2
• CT venography can be used if MRI is not readily available in emergency settings 1
• Gradient echo T2 susceptibility-weighted images combined with MR venography improve diagnostic accuracy 3, 1
• Non-contrast CT has limited sensitivity (abnormal in only 30% of cases) but may show:
  • "Empty delta" sign on contrast-enhanced CT (characteristic of CVST) 2
  • Hyperdensity of cortical vein or dural sinus in acute phase 2
• Catheter cerebral angiography may be necessary for inconclusive CTV or MRV results with high clinical suspicion 3, 1

Diagnostic Pitfalls

• Anatomic variants may mimic sinus thrombosis (sinus atresia/hypoplasia, asymmetrical sinus drainage) 3, 1
• Flow gaps commonly seen on TOF MRV images can affect interpretation 3
• Delayed diagnosis is common due to variable presentation and slower progression (median 7 days from symptom onset to diagnosis) 2
• CVST may be misdiagnosed as idiopathic intracranial hypertension, especially with isolated headache and papilledema 2

Treatment

• Immediate anticoagulation should be started with either intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin, even in patients with hemorrhagic lesions related to CVST. 1, 4
• Anticoagulation prevents thrombus propagation, increases recanalization, and reduces mortality and severe disability 1, 4
• Duration of anticoagulation depends on risk factors:
  • Transient reversible risk factors: 3-6 months of oral anticoagulation 1
  • Idiopathic CVST or mild thrombophilia: 6-12 months 1
  • High-risk inherited thrombophilia or recurrent events: Consider indefinite (lifelong) anticoagulation 1
• For severe cases with neurological deterioration despite anticoagulation, consider:
  • Endovascular thrombolysis 1, 2
  • Decompressive hemicraniectomy for severe mass effect 2

Management of Complications

• Elevated intracranial pressure: Consider dexamethasone (4-8 mg/day oral or IV) only for patients with significant white matter edema causing mass effect 1, 4
• Seizures: Treat aggressively with antiepileptic medications 1
• Follow-up imaging: CTV or MRV at 3-6 months to assess recanalization 3, 1
• Early follow-up imaging for persistent or evolving symptoms despite treatment 3, 1

Prognosis

• Favorable outcomes in most cases with early diagnosis and prompt treatment 5
• Mortality and severe disability rates have decreased significantly with modern management 6
• Approximately 25% of patients may still experience acute complications or chronic disability 7