Cerebral Venous Sinus Thrombosis (CVST)
Cerebral venous sinus thrombosis (CVST) is a rare form of stroke caused by a blood clot within the dural venous sinuses.
Relevant Anatomy
The brain is drained by a venous system
- Cerebral veins drain blood from the brain tissue itself
- Cerebral veins drain into the dural venous sinuses – large venous channels located between layers of the dura mater
- Dural venous sinuses also receive CSF via arachnoid granulations, and carry blood to the internal jugular vein
Key dural venous sinuses:
| Dural venous sinus | Location / anatomical relevance |
|---|---|
| Superior sagittal sinus | Runs along the top midline of the skull
Most commonly affected in CVST |
| Inferior sagittal sinus | Runs along the lower free edge of the falx cerebri |
| Straight sinus | Located at the junction of the falx cerebri and tentorium cerebelli
Receives venous drainage from the inferior sagittal sinus, then drains into the confluence of sinuses |
| Transverse sinuses | Run laterally from the back of the skull |
| Sigmoid sinuses | Continue from the transverse sinuses and drain into the internal jugular veins |
| Cavernous sinus | Either side of the sella turcica
Contains CN III, IV, V1, V2, VI and ICA |
Causes and Risk Factors
| Category | Risk factors |
|---|---|
| Oestrogen-related factors | The following contribute to marked female predominance (3x risk than men) in CVST cases among young adults (women of childbearing age account for 70-80% of cases)
|
| Infections |
|
| Thrombophilia |
|
| Direct injury and other triggers | Physical or mechanical disruptions can also provoke thrombosis
|
Clinical Features
Onset of CVST: [Ref]
- Subacute (over 48 hours and 4 weeks) in ~60% cases
- Acute (under 48 hours) in ~37% cases
Typical clinical features: [Ref]
- Headache – most common symptom (typically diffuse / generalised, worsening gradually over days and is not relieved by sleep)
- Focal neurological deficit (esp. motor weakness)
- Unlike in typical arterial strokes, neurological deficits in CVST do NOT localise to a single vascular territory
- Cerebral dysfunction (e.g. aphasia, neglect) may occur but are less typical than in arterial stroke
- Seizures (esp. focal seizure, which may progress into generalised seizure or status epilepticus)
- Signs of raised ICP (e.g. papilloedema, diplopia, nausea and vomiting)
Severe presentations may occur with straight sinus involvement, extensive thrombosis, or severe venous infarction with haemorrhagic transformation, leading to encephalopathy, reduced consciousness or coma.
Cavernous sinus thrombosis – a specific form of venous sinus thrombosis involving the cavernous sinus, typically presents as:
- Fever (often infective in origin, e.g. sinusitis)
- Periorbital swelling / oedema
- Proptosis, chemosis, ophthalmoplegia, diplopia
- Reduced visual acuity
- Reduced corneal reflex / facial sensory loss (from CN V1 and V2 involvement)
Secondary intracranial haemorrhage is an important complication of CVST, usually due to venous congestion and haemorrhagic venous infarction. [Ref]
It may present as intraparenchymal haemorrhage, subarachnoid haemorrhage or other patterns of intracranial bleeding. [Ref]
Investigation and Diagnosis
In short, investigation of choice: CT / MR venogram
- CT venogram is often performed initially, esp. in the acute setting
- MR venogram is the gold standard with superior sensitivity
- Diagnostic finding: filling defect or absent flow within a dural venous sinus or cortical vein
In practice, there are 2 main clinical scenarios:
| Scenario | Approach |
|---|---|
| CVST is strongly suspected based on clinical features and history | Investigation of choice: CT / MR venogram to confirm the diagnosis
A non-contrast CT head is usually performed together with the venogram to look for haemorrhage, mass effect and alternative diagnoses. |
| Acute stroke is suspected generally | Initial investigation: non-contrast CT head
If CT shows features suggestive of CVST (e.g. hyperdense clot within a dural venous sinus or cortical vein) → urgent CT / MR venogram to confirm the diagnosis |
Management
Primary initial treatment: full-dose anticoagulation with heparin
- It is very common for a CVST to cause a secondary cerebral haemorrhage
- Full-dose anticoagulation must still be given even if imaging shows a secondary cerebral haemorrhage
Long-term maintenance therapy:
- Warfarin for at least 3 months (target INR: 2-3)
The following are NOT recommended:
- DOACs (even though they are widely used as 1st line anticoagulation in VTEs)
- Corticosteroids
- Reperfusion therapy (thrombolysis and thrombectomy)