Cerebral Venous Sinus Thrombosis
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Direct answer
Cerebral venous sinus thrombosis is obstruction of the dural sinuses or cortical veins by thrombus, causing raised intracranial pressure, venous infarction and haemorrhage, most often in young women on oral contraceptives or in the puerperium. Headache with focal features, seizures or papilloedema points toward it, and MR venography confirms it, after which anticoagulation is given even when the infarct is haemorrhagic.
What you must remember
- Commonest site: the superior sagittal sinus, followed by the lateral transverse sinuses; thrombosis of the deep cerebral veins involving the thalami causes bilateral features.
- Risk factors: oral contraceptives, pregnancy and puerperium, dehydration, ear or sinus infection, malignancy, and thrombophilia such as factor V Leiden or antiphospholipid syndrome.
- Presentation: headache is commonest, with seizures, focal deficits, papilloedema and reduced consciousness; onset can be subacute over days.
- Empty delta sign: on contrast CT, an empty triangular filling defect is outlined by enhancing dura within the sinus; on non-contrast CT a hyperdense sinus is the cord sign.
- Best test: MR venography or CT venography confirms the diagnosis; a normal conventional CT does not exclude thrombosis.
- Anticoagulation: heparin, then warfarin (or a DOAC in many centres) for a defined period, is given even with haemorrhagic infarction, unless the bleed is large enough to contraindicate it.
- Raised pressure: repeated lumbar puncture, acetazolamide and, if the patient deteriorates, endovascular therapy or decompressive surgery.
- Seizures: treated with antiseizure drugs; prophylaxis is not routinely given to patients who have never had a seizure.
Worked example: headache and a seizure after delivery
A 27-year-old woman three weeks after delivery presents with a severe headache that has worsened over five days, then a focal seizure involving the right arm. She is conscious, with papilloedema on fundoscopy and mild right arm weakness, and her initial CT is reported as normal, a reason for caution rather than reassurance.
- Refuse false reassurance: A normal conventional CT does not exclude thrombosis, so venous imaging is still needed.
- Image the venous system: MRI with diffusion imaging and MR venography show thrombosis of the superior sagittal sinus with a small haemorrhagic venous infarct over the left parietal lobe.
- Anticoagulate despite the bleed: She receives therapeutic low-molecular-weight heparin, since haemorrhagic infarct alone does not stop anticoagulation.
- Treat the seizure: An antiseizure drug is started for the seizure.
- Defer the lumbar puncture: Lumbar puncture waits until imaging is complete, because herniation risk is why imaging comes first.
- Defer thrombophilia testing: Thrombophilia screening waits for the acute phase, since results change little while the thrombus is active.
- Plan the follow-up: Follow-up imaging checks recanalisation and sets the anticoagulation duration, which depends on whether the thrombosis was provoked. Heparin and warfarin are both compatible with breastfeeding.
Where the diagnosis is missed
A normal scan often misses this thrombosis, and the same few errors recur in examinations.
- Trap: accepting a normal CT as excluding the diagnosis. Correct: venous imaging is needed, since a normal conventional CT does not exclude thrombosis.
- Trap: confusing the empty delta sign with the cord sign. Correct: the empty delta is a contrast CT filling defect, whereas the cord sign is a hyperdense sinus on non-contrast CT.
- Trap: withholding anticoagulation because of bleeding on imaging. Correct: standard teaching is to anticoagulate unless the bleed is large or the patient is deteriorating.
- Trap: missing the trigger hidden in the stem. Correct: oral contraceptives, the puerperium or a dehydrated patient with an ear or sinus infection should be named, as part of the answer.
Frequently asked questions
Which imaging test confirms cerebral venous sinus thrombosis?
MR venography, or CT venography, confirms cerebral venous sinus thrombosis by showing absent flow in the affected sinus. MRI with diffusion imaging adds information on venous infarction and haemorrhage, and a normal conventional CT does not exclude the diagnosis.
What is the empty delta sign in cerebral venous sinus thrombosis?
The empty delta sign is a triangular filling defect within a dural sinus on contrast-enhanced CT, outlined by enhancing dura around the thrombus. It is a classic sign of cerebral venous sinus thrombosis and is distinct from the cord sign seen on non-contrast CT.
Is anticoagulation given in cerebral venous sinus thrombosis with haemorrhage?
Anticoagulation is generally given in cerebral venous sinus thrombosis even when there is haemorrhagic venous infarction, because the thrombus is the cause and stopping treatment risks extension. It is withheld only when the bleed is large or the patient deteriorates despite treatment.
Which risk factors predispose young women to cerebral venous sinus thrombosis?
Oral contraceptive use, pregnancy and the puerperium are the commonest risk factors for cerebral venous sinus thrombosis in young women. Dehydration, ear or sinus infection and inherited thrombophilia such as factor V Leiden also raise the risk.
Which symptoms of cerebral venous sinus thrombosis should prompt urgent imaging?
Headache with seizures, focal deficits, papilloedema or reduced consciousness should prompt urgent imaging for cerebral venous sinus thrombosis. A severe or progressive headache in a young woman using oral contraceptives or in the puerperium is a further reason to image the venous system.