21.3 Cerebral Venous Sinus Thrombosis (03.F)

Cerebral venous thrombosis (CVT) — also called cerebral venous sinus thrombosis (CVST) when the large sinuses are involved — is a clot in the cerebral veins or dural sinuses. Arterial stroke algorithms miss it because the infarct is often hemorrhagic, bilateral, or in a territory no named artery owns. Incidence is on the order of 1–2 per 100,000 per year in adults, with a strong tilt toward women of childbearing age. The International Study on Cerebral Vein and Dural Sinus Thrombosis (ISCVT) taught the modern natural history: most patients are young, headache is nearly universal, seizures are common (~40%), and about 80% regain independence — if you anticoagulate and treat intracranial hypertension instead of withholding heparin because the CT already shows blood.

The 2011 AHA/ASA scientific statement (Saposnik and colleagues) established heparin-despite-hemorrhage as standard teaching. The 2024 AHA scientific statement (Saposnik G et al., Stroke 2024;55:e77–e90) updates diagnosis and the oral-anticoagulant era, including direct oral anticoagulants (DOACs) as an option after the acute parenteral phase in selected patients. European Stroke Organization 2017 guidance and Canadian 2024 best-practice recommendations agree on the hemorrhage point: intracranial or subarachnoid blood is not a contraindication to anticoagulation.

Independent OpenExamPrep coverage of this ABIM Neurocritical Care disease should stay concrete: recognize the syndrome, pick the venogram, start heparin, hunt the cause, and reserve endovascular therapy for true rescue.

Clinical picture that is not an MCA occlusion

Headache is the dominant symptom and may be thunderclap, subacute, or chronic and papilledema-like. Seizure — including status epilepticus — is far more common than in arterial ischemic stroke. Focal deficits follow the occluded sinus:

Papilledema and a high opening pressure on lumbar puncture (once imaging has excluded a mass that forbids LP) mark the isolated-intracranial-hypertension phenotype, which can mimic idiopathic intracranial hypertension. A venous infarct that crosses arterial territories, is hemorrhagic from the start, or sits in the parasagittal or bithalamic regions is CVT until venography says otherwise.

Risk factors the exam expects you to name

A young woman with a new combined oral contraceptive, a week of headache, and a left temporal hematoma is a CVT stem, not a hypertensive ICH stem. Mastoiditis plus a transverse-sinus clot is infection plus thrombosis: drain the ear, culture, antibiotics, and anticoagulate.

Imaging: CTV, MRV, and the traps of noncontrast CT

Noncontrast CT is often the first scan and is frequently normal or nonspecific. Clues, when present:

• Hyperdense triangle (acute clot in the superior sagittal sinus)
• Empty delta sign on contrast CT (enhancing dura around a nonenhancing clot)
• Hemorrhagic infarct that is not wedge-shaped in an arterial map

Definitive noninvasive tests are CT venography (CTV) and MR venography (MRV). MRI also shows the parenchyma: DWI/ADC of venous infarction, blooming on susceptibility-weighted images in a cortical vein, and edema that looks "too much" for the amount of hypodensity. Time-of-flight MRV can overcall hypoplastic transverse sinuses; contrast-enhanced MRV or CTV helps. Catheter cerebral venography is reserved for diagnosis that remains uncertain or for endovascular treatment.

Do not wait for a perfect MRI in a seizing, herniating patient: CTV on the way to the ICU is enough to start heparin.

Anticoagulation even when there is blood

The clot is causing venous hypertension; the hemorrhage is often a venous hemorrhagic infarct. Leaving the sinus occluded lets edema and bleeding worsen. Randomized data are old and small (intravenous unfractionated heparin versus placebo; nadroparin versus placebo), but they, plus two decades of observational practice, underpin every major statement:

• Start therapeutic heparin — unfractionated heparin (UFH) infusion or low-molecular-weight heparin (LMWH).
• Presence of intracranial hemorrhage or convexity SAH is not a reason to withhold anticoagulation.
• UFH is convenient when an EVD, craniectomy, or other procedure is likely (short half-life).
• LMWH is reasonable in stable patients who are unlikely to need an immediate operation.
• Avoid heparin if there is heparin-induced thrombocytopenia; use an alternative anticoagulant with hematology.

After a parenteral lead-in (often several days to 2 weeks, individualized), transition to oral therapy. Traditional course: vitamin K antagonist with INR target 2–3 for 3–12 months if the trigger was transient, longer or indefinite if the thrombophilia or cancer is permanent. The 2024 AHA statement and subsequent summaries include DOACs as an alternative to warfarin in selected lower-risk patients, supported by small randomized trials (including RE-SPECT CVT with dabigatran) and observational series. DOACs are not first-line in antiphospholipid syndrome (warfarin remains preferred) or in pregnancy (LMWH). There is still insufficient evidence to skip parenteral therapy and start a DOAC as the very first anticoagulant in acute severe CVT.

Endovascular rescue, ICP, and seizures

The TO-ACT randomized trial of endovascular thrombolysis/thrombectomy plus anticoagulation versus anticoagulation alone did not show a benefit that would make catheter therapy routine. AHA 2024-era teaching: endovascular treatment is selected rescue — clinical deterioration from clot propagation or refractory intracranial hypertension despite anticoagulation, or perhaps a comatose deep-venous occlusion at a center that does this work. It is not the opening move for an awake patient with a transverse-sinus clot and a small hematoma.

Mass effect and herniation: osmotherapy as a bridge; decompressive craniectomy can be life-saving in young patients with large venous infarcts and is supported by registry data and European guidance even without a dedicated RCT. That is one of the better craniectomy stories in all of stroke.

Seizures: treat clinical seizures; prophylactic antiseizure drugs in patients who have not seized are not routinely recommended. Acute symptomatic seizures (within 7 days) get treated per usual ICU protocols.

Acetazolamide or therapeutic lumbar puncture may help the isolated-intracranial-hypertension phenotype after imaging clearance. Steroids are not a routine CVT treatment except when the cause is inflammatory disease that independently needs them.

Workup for cause

Once the patient is anticoagulated and the brain is not herniating, find why:

• History of OCP, pregnancy, miscarriage, cancer, IBD, ear infection
• CBC (myeloproliferative disease), pregnancy test
• Antiphospholipid antibodies (can be sent acutely)
• Inherited thrombophilia panel: some proteins fall in acute thrombosis, so protein C, protein S, and antithrombin are more reliable later, off anticoagulation, unless you use assays that heparin/DOAC do not wreck
• Blood cultures and ear imaging if fever or mastoid tenderness
• Age-appropriate cancer screening when unprovoked and older
• HIT/VITT testing only when the clinical context fits

Counsel estrogen users to stop combined contraceptives. Future pregnancy is not forbidden after CVT; it is a high-risk hematology/OB collaboration, usually with LMWH prophylaxis in subsequent pregnancies depending on the original trigger.

In practice

A 29-year-old on a combined oral contraceptive has a week of headache, then a seizure. CT shows a left temporal hematoma that does not look like an MCA wedge. CTV shows left transverse- and sigmoid-sinus thrombosis. You start unfractionated heparin despite the hematoma, treat the seizure, obtain MRI, and screen for thrombophilia and mastoid disease. If she later herniates from swelling, you consider decompression, not reversal of heparin as the first and only move. If she is stable after a heparin lead-in and has no antiphospholipid syndrome, a DOAC or warfarin for months is consistent with the 2024 AHA statement. If she deteriorates with expanding thrombosis despite therapeutic heparin, that is the setting for a selected endovascular rescue discussion — not TO-ACT-for-everybody.