Cerebral Venous Thrombosis (CVT)

What happens in cerebral venous thrombosis

Blood leaves the brain through veins that drain into large channels called dural venous sinuses, which run between layers of tissue covering the brain and empty into the jugular veins in the neck. When a clot blocks a sinus or vein:

• blood backs up into the brain, causing swelling (edema)
• pressure inside the skull rises, causing headache and swelling of the optic nerves (papilledema)
• small veins may burst, causing bleeding into the brain (venous hemorrhage)
• the brain absorbs less cerebrospinal fluid

Because veins have many connections, symptoms often develop more gradually than in arterial strokes.

Symptoms

• Headache: present in about 9 in 10 people. Usually builds over days, can be severe, often worse lying down or with coughing. Less commonly it is sudden (thunderclap).
• Vision problems: blurred or double vision, temporary dimming, from raised pressure.
• Seizures: more common than in arterial stroke.
• Focal symptoms: weakness or numbness of one side, speech problems.
• Confusion, drowsiness or reduced consciousness.
• Nausea and vomiting.

Some people have only a headache with signs of raised pressure, which can look like idiopathic intracranial hypertension (pseudotumor cerebri).

Causes and risk factors

Most people have at least one identifiable risk factor:

• Hormonal factors: combined oral contraceptives, hormone therapy, pregnancy and especially the weeks after childbirth.
• Clotting disorders (thrombophilia): inherited, such as factor V Leiden, prothrombin gene mutation and protein C, protein S or antithrombin deficiency, or acquired, such as antiphospholipid syndrome.
• Infections: of the ear (mastoiditis), sinuses, face or brain coverings, and in children, dehydration with infections.
• Cancer and some cancer treatments.
• Inflammatory diseases: inflammatory bowel disease, lupus, Behçet's disease.
• Dehydration, obesity and anemia.
• Head injury, neurosurgery or lumbar puncture.
• Vaccine-induced immune thrombotic thrombocytopenia (VITT): a rare reaction to adenovirus-vector COVID-19 vaccines, involving clots with low platelets.

Diagnosis

CVT can be hard to spot because the headache resembles more common headaches. Clues include a progressive headache, papilledema seen on eye examination, and risk factors such as pregnancy or the pill.

• MRI with MR venography (MRV): the preferred test, showing the clot and any brain damage.
• CT with CT venography (CTV): quick and widely available, especially in emergencies.
• Blood tests: blood count (including platelets), clotting tests, inflammation markers, and later testing for thrombophilia when appropriate. A normal D-dimer makes CVT less likely but does not rule it out.
• Eye examination for papilledema, and sometimes a lumbar puncture to measure pressure once the clot is confirmed.

Treatment

• Anticoagulation (blood thinners): the main treatment. Heparin is started immediately, even when there is bleeding into the brain, because stopping clot growth reduces further bleeding. It is followed by oral anticoagulants, usually for 3 to 12 months, or longer if there is an ongoing clotting tendency or repeated clots.
• Treat the cause: antibiotics and sometimes surgery for infection, stopping estrogen-containing contraceptives, and hydration.
• Seizure control with anti-seizure medicines.
• Lowering pressure in the skull: medicines, removal of spinal fluid, or in severe cases surgery to relieve pressure (decompressive craniectomy).
• Endovascular therapy: removing or dissolving the clot through a catheter is considered for people who worsen despite anticoagulation.
• Vision monitoring if pressure has affected the optic nerves.
• VITT needs specific treatment, including avoiding heparin and giving IV immunoglobulin.

Outlook

Most people, roughly 8 in 10, recover well with treatment and become independent again. Headaches, tiredness, mood changes and concentration problems can persist for months. A small proportion have lasting disability or die, mainly those with deep vein involvement, coma, large bleeds or cancer. The risk of another clot is low but higher than average.

Pregnancy and contraception after CVT

Estrogen-containing contraceptives are usually avoided after CVT. Progestin-only methods and copper IUDs are generally considered safer options. Future pregnancy is usually possible, but preventive blood thinners (low molecular weight heparin) are often recommended during pregnancy and after delivery. Plan with your specialists.

Frequently asked questions

What are the symptoms of cerebral venous thrombosis?

The most common symptom is a headache that gets worse over days, often with nausea and vomiting and worse when lying down. Other symptoms include blurred or double vision, seizures, weakness or numbness on one side, speech problems and confusion. Any of these need urgent medical assessment.

What causes cerebral venous sinus thrombosis?

Common causes and risk factors include pregnancy and the period after childbirth, combined contraceptive pills, inherited or acquired clotting disorders, infections of the ear, sinuses or face, cancer, inflammatory diseases and dehydration. Many people have more than one factor.

Is cerebral venous thrombosis a stroke?

Yes. CVT is an uncommon type of stroke caused by a clot in the veins that drain the brain, rather than in the arteries that supply it. It accounts for a small fraction of all strokes and more often affects younger adults and women.

Can you recover from cerebral venous thrombosis?

Most people recover well with prompt anticoagulant treatment, and around 8 in 10 regain independence. Headaches, fatigue and concentration problems can linger for months. Outcomes are worse with severe bleeding, coma or underlying cancer.

Why are blood thinners used if there is bleeding in the brain?

In CVT, bleeding is caused by blocked veins backing up and bursting. Blood thinners stop the clot from growing and help the veins reopen, which lowers pressure and reduces further bleeding. Studies support using them even when a bleed is present.