Transverse sinus thrombosis is a blood clot in one of the two transverse sinuses, large venous channels at the back of the skull that carry blood out of the brain. It usually causes a worsening headache, and sometimes vision problems, seizures, or weakness. It is diagnosed with MR or CT venography and treated first with anticoagulant (blood-thinning) medication. Most people who are diagnosed promptly and treated make a good recovery, which is why recognizing the warning signs matters.
Transverse sinus clots are a form of cerebral venous sinus thrombosis (CVST), and the transverse sinus is one of the sites most often involved. Below, I walk through the anatomy, causes, symptoms, tests, and treatment from a hematologist’s point of view.
What Is Transverse Sinus Thrombosis?
The brain’s blood drains through a network of dural venous sinuses, channels that sit between layers of the tough membrane lining the skull. Blood from the top of the brain flows back through the superior sagittal sinus to a junction at the back of the head, then divides into the left and right transverse sinuses. Each transverse sinus curves forward into the sigmoid sinus, which empties into the internal jugular vein in the neck.
When a clot blocks a transverse sinus, blood backs up. Pressure inside the skull can rise, and the veins that drain into that sinus, including the large vein of Labbé over the temporal lobe, can become congested. In more serious cases this leads to swelling, a venous infarct (tissue damage from poor drainage), or bleeding into the brain.
The two transverse sinuses are often unequal in size. A naturally small, or hypoplastic, transverse sinus is a common normal variant, and it can be mistaken for a clot on imaging. Radiologists take care to distinguish the two.
Causes and Risk Factors
Like other venous clots, transverse sinus thrombosis usually results from a combination of factors that make blood more likely to clot, slow the flow, or damage the vessel wall. Often more than one is present.
| Category | Examples |
|---|---|
| Hormonal | Combined oral contraceptives, pregnancy, the weeks after childbirth, estrogen therapy |
| Inherited thrombophilia | Factor V Leiden, prothrombin gene mutation, deficiencies of protein C, protein S, or antithrombin |
| Acquired clotting disorders | Antiphospholipid syndrome, cancer, myeloproliferative neoplasms, nephrotic syndrome |
| Local causes | Middle ear infection or mastoiditis spreading to the nearby sinus, head injury, neurosurgery |
| General conditions | Severe dehydration, inflammatory bowel disease, lupus, some infections, anemia from iron deficiency |
Because the transverse and sigmoid sinuses lie right next to the mastoid bone, ear infections are a classic cause of clotting on one side, sometimes called lateral sinus thrombosis. In adults, hormonal factors are among the most frequent triggers, which is one reason the condition is seen more often in younger women.
Symptoms and Clinical Presentation
Headache is the most common symptom. It often builds over days, may be worse lying down or on waking, and does not respond well to usual painkillers. Occasionally it starts suddenly, like a thunderclap.
Other features depend on how much pressure builds up and whether brain tissue is affected:
- Raised intracranial pressure: blurred or double vision, nausea, vomiting, and swelling of the optic discs (papilledema) seen by an eye examination.
- Seizures: focal or generalized, more likely if there is a venous infarct or bleed.
- Focal neurological signs: weakness, numbness, or, with left temporal lobe involvement, difficulty with speech and language.
- Reduced alertness or confusion in more severe cases.
- Ear symptoms: ear pain, discharge, or fever when infection is the cause.
Diagnosis and Testing
The key tests are imaging of the veins. MR venography (MRV) combined with MRI of the brain is often the preferred study, as it shows the clot and any effect on brain tissue. CT venography is fast, widely available, and highly accurate, making it a common first test in the emergency department. A plain CT scan may be normal or show subtle signs, so it cannot rule out the diagnosis on its own.
Blood tests support the workup. A normal D-dimer makes a clot less likely, but it does not exclude one, particularly when headache is the only symptom or symptoms have been present for some time. A full blood count can reveal clues such as a raised platelet count or hemoglobin pointing to a myeloproliferative neoplasm. Thrombophilia testing, pregnancy testing, and checks for infection or inflammation are tailored to the individual. The broader picture of sinus thrombosis diagnosis and emerging treatments is covered in a companion article.
Treatment and Recovery
Anticoagulation is the cornerstone of treatment. Low molecular weight heparin or intravenous unfractionated heparin is started as soon as the diagnosis is confirmed. This is true even when there is some bleeding in the brain caused by the venous blockage, because stopping the clot from growing is the best way to relieve the pressure that caused the bleed. Anticoagulants do not dissolve the clot directly; they prevent extension and let the body’s own systems gradually reopen the vessel.
After the acute phase, treatment usually continues with an oral anticoagulant, either warfarin or, increasingly, a direct oral anticoagulant. Typical durations are:
- 3 to 6 months when there was a clear temporary trigger, such as pregnancy or an infection.
- 6 to 12 months when no cause is found.
- Longer or indefinite treatment for recurrent clots or severe inherited or acquired thrombophilia.
Supportive care matters too: seizure medication when seizures occur, treatment of infection (sometimes with ear surgery), stopping estrogen-containing medicines, and monitoring of vision if pressure is high. For the small number of patients who worsen despite anticoagulation, specialist centers may consider endovascular treatment to remove or dissolve the clot, and decompressive surgery is reserved for life-threatening brain swelling. You can explore related topics in our blood clotting guide.
When to See a Doctor
Seek urgent medical care for a new, severe, or steadily worsening headache, especially if it comes with vision changes, vomiting, a seizure, weakness, confusion, or if you are pregnant, recently gave birth, or take hormonal contraception. A headache alongside a painful, discharging ear and fever also needs prompt review. Early treatment makes a meaningful difference to recovery.
Frequently Asked Questions
Is transverse sinus thrombosis a stroke?
It is considered an uncommon type of stroke because it can damage brain tissue. Unlike the more common arterial stroke, the problem is blocked drainage rather than blocked blood supply. It tends to affect younger people and often has a better outlook when treated early.
Can the clot come back?
Recurrence is possible but not common, and it is more likely with an ongoing risk factor such as a strong thrombophilia. Your hematologist will weigh this when deciding how long to continue anticoagulation.
Can I use hormonal contraception again afterward?
Estrogen-containing contraceptives are generally avoided after a cerebral venous clot. Progestogen-only and non-hormonal options are usually preferred, and the choice should be discussed with your doctor.
Will the sinus fully reopen?
Many sinuses partly or fully recanalize over the following months, but some remain narrowed without causing symptoms. Good recovery depends more on symptom resolution than on the sinus looking completely normal on follow-up imaging.
