Diagnosis of cerebral venous sinus thrombosis

David Goldemund M.D.
Updated on 08/05/2024, published on 07/04/2020
  • establishing the diagnosis of Cerebral Venous Sinus Thrombosis (CVST) is often difficult in the early stages; the temporal course and clinical symptoms are variable and often nonspecific
  • focal neurological symptoms typically occur in association with venous infarcts
  • exclude CVST in the presence of:
    • intracranial hypertension syndrome
    • atypical ischemias – especially those with atypical localization, not respecting traditional arterial territories, and featuring a hemorrhagic component or edema
    • first epileptic seizure (especially in young women)
    • hyperdense sign on noncontrast CT
  • if CVST is suspected, imaging modalities such as MR imaging and MR venography (MRV) or CT venography (CTV) can help confirm the diagnosis


  • neuroimaging is essential for the diagnosis of cerebral venous sinus thrombosis
  • CT is widely available and is the most commonly used baseline imaging modality, although MRI with venous TOF sequence is preferred (especially in pregnancy)
When should you think about cerebral venous sinus thrombosis?
Direct signs of thrombus in the vein/dural sinus
dense clot sign (delta sign)   Dense clot sign (75HU) on NCCT - thrombosis of the right transverse sinus Dense clot sign (delta sign) - thrombosis of the superior sagittal sinus
cord sign Cord sign - thrombosis of the superficial cerebral veins
empty delta sign (contrast-enhanced CT) Empty delta sign on postcontrast CT scan
absent flow void in T2/FLAIR Absence of flow void in the left sigmoid sinus (FLAIR)
Indirect signs
  • lateral, parasagittal, and bithalamic infarcts with/without hemorrhage  Hemorrhagic infarction in thrombosis of the left transverse and sigmoid sinus The straight sinus thrombosis with bithalamic venous infarction Venous infarction (NCCT)
  • cortical edema
  • peripheral lobar hematomas  Thrombosis of the left ascendent vein   Hemorrhagic venous infarction in thrombosis of transverse and superior sagittal sinus

CT + CT venography

  • non-contrast CT scan (NCCT) of the brain is normal in up to 30% of cases
  • always evaluate separately
    • non-contrast CT images (hyperdensity sign – cord sign, dense clot sign) – positive in 25% of cases
    • contrast-enhanced CT images (empty delta sign) – positive in 16-46%
  • indirect signs of thrombosis include edema, an atypically located infarct, often with a hemorrhagic component
  • a hyperdense sign may be false-positive; additional signs are required for diagnosis
    • a false-positive finding in cases of polyglobulia
    • typical values with CVT are > 70 HU  The right sigmoid and transverse sinus thrombosis - hyperdense sign with 80HU  Thrombosis of the right transverse sinus (maximum density 83 HU)  [Black, 2011]
  • a CT scan may detect associated inflammatory changes (such as otitis, mastoiditis, sinusitis)
Transverse, sigmoid and superior sagittal sinus thrombosis (NCCT)

Transverse and superior sagittal sinus thrombosis

Straight sinus thrombosis (NCCT)

  • CT venography (CTV) is a reliable alternative to MR venography (MRV) or digital subtraction angiography (DSA) (ESO guidelines 2017)
    • a time delay of 25-45 seconds compared to CTA is recommended
    • sensitivity for dural sinus thrombosis is up to 95% compared to DSA
    • alternative to MRV – MRI offers superior visualization of thrombus and parenchymal changes
    • disadvantages:
      • difficulty distinguishing between sinus hypoplasia and aplasia (5-20% of cases)
      • exposure to radiation and contrast media
      • limited diagnostic value in cortical vein thrombosis
Hyperdense sign on NCCT (left), CT venography with defective contrast filling of the right transverse and sigmoid sinuses
The right sigmoid and transverse sinus thrombosis. Non-contrast CT shows a hyperdense sign with 80 HU. CT venography confirmed sinus thrombosis

MRI + MR venography

  • hyperintense venous infarct in an atypical location, often with a hemorrhagic component and edema Lesions in the posterior part of the right temporal lobe (mixed signal in FLAIR, blood on GRE). The right transverse and sigmoid sinus do not appear as a result of thrombosis Venous infarction in patient with the superior sagittal and right transverse sinus thrombosis
    • typically found in parasagittal and temporal regions
    • DWI may show decreased, normal, increased, or a mixture of diffusivity in areas of venous infarction
    • hemorrhage may vary from large hematomas to petechial hemorrhages within edematous tissue
  • T2 and FLAIR sequences typically demonstrate the absence of a flow void (sinuses are usually hypointense)   Absence of flow void in the left sigmoid sinus (FLAIR)
    • thrombosis < 24h or > 3 days
  • thrombus in the acute stage (within 3 days) can be confused with normal flow void, as it is T1/T2 hypointense during this period
  • from day 4, the thrombus should become hyperintense (bright)  Thrombosis of the right transverse sinus
  • beware of potential confusion with hypoplasia (assess the size of the jugular foramen for differentiation)
  • on GRE/SWI, the thrombus appears hypointense in the vein or sinus  (DDx of a small SAH) The straight sinus thrombosis (hypointense on GRE) Cord sign on GRE Superficial vein thrombosis, superior sagittal sinus and the left transverse sinus (GRE)
  • MR venography (MRV) uses the time-of-flight (TOF) technique; the assessment may be complicated by sinus hypo- or aplasia or asymmetric flow The transverse sinus thrombosis (MR venography)
    • MRV is considered a reliable alternative to DSA for diagnosing cerebral venous sinus thrombosis  (ESO guidelines 2017)
Superior sagittal and transverse sinus thrombosis

Transverse sinus thrombosis

Superior sagittal sinus and transverse sinus thrombosis (FLAIR)

The superior sagittal sinus and the right transverse sinus thrombosis in a 24-year-old female patient. Hyperintense sinuses in T2 , T1 and FLAIR, hypointensities in the thrombosed sinuses on GRE and absence of sinus filling on MR venography

Digital subtraction angiography

  • consider possible anatomical variants of the venous system, including hypoplasia or the absence of some vessels
  • a specific indicator for CVST diagnosis is the presence of a “stop sign” (abrupt termination of a sinus or vein) accompanied by collateral circulation and congestion of cortical veins (characterized by dilation, tortuosity)  The right transverse and sigmoid sinus thrombosis The superior sagittal sinus thrombosis on DSA
  • DSA may show associated cortical vein thrombosis and possibly arterio-venous fistula as well as deep vein thrombosis
  • in addition, DSA shows the dynamics and drainage pattern in the occluded area
    • after applying the contrast agent, the venous system is completely visualized within 7-8 seconds
    • in cases of thrombosis, the filling of the veins is delayed or absent
  • currently, MRV and CTV dominate the diagnostic workup, and DSA is reserved for interventional procedures when conservative therapy fails


  • the method has low sensitivity and specificity
    • indirect signs are mostly evaluated: flow acceleration (> 40 cm/s) due to collateral circulation
  • sigmoid sinus (SS) thrombosis may be monitored by examining flow in the ipsilateral internal jugular vein (IJV) Occlusion of the right sigmoid sinus and IJV
  • more information on TCCD examination of cerebral veins and sinuses is here

Additional diagnostic studies


  • normal D-dimer levels: 0.068-0.494 mg/L
  • may serve as an important screening tool (with sensitivity > 95%); testing D‐dimer together with fibrinogen may increase specificity
    • the sensitivity and specificity using D-dimer alone were 94·1% and 97·5%, whereas those for D-dimer + fibrinogen were 67·6% and 98·9%  [Meng,2013]
    • elevated levels can occur in various conditions, including infection, trauma, or malignancy
  • a normal D-dimer level makes the diagnosis of acute thrombosis unlikely but does not definitively exclude it (AHA/ASA 2011 IIb/B) [Kosinki, 2005] [Lalileve,2003]
    • positive in ~ 94% of patients with CVT (ESO guidelines 2017)
    • a false-negative result may be seen in cases of isolated headache and prolonged thrombosis (lasting > 1 week)
  • on the other hand, false-positive results are common (see below)
  • after anticoagulation therapy, D‐dimer levels gradually normalize;  fibrinogen levels may remain elevated for several weeks
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Lumbar puncture

  • perform a lumbar puncture to rule out an infectious etiology (if suspected)
  • drainage of ∼ 20-30 mL of cerebrospinal fluid (CSF) may alleviate pain or prevent vision loss
  • typical signs of venous thrombosis include increased opening pressure, proteinorhachia, and occasionally mild pleocytosis
    • mild pleocytosis may lead to misdiagnosis of neuroinfection
  • lumbar puncture is contraindicated in the presence of an expansive parenchymal lesion

Other laboratory studies

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  • pathological findings are predominantly associated with parenchymal lesions
  • if mental status is altered, nonconvulsive status epilepticus (NCSE) should be excluded

Differential diagnosis

  • high-flow dural A-V fistula can lead to venous congestion and subsequent hemorrhagic infarction (which can be difficult to distinguish from a venous thrombosis)
  • headache and encephalopathy are less common in ischemic stroke
  • compared to ischemic stroke, infarct lesions in CVST differ in shape and location
  • in CVST, hemorrhagic transformation and collateral edema are commonly observed on baseline imaging
  • look for signs of inflammation – fever, leukocytosis with elevated CRP and ESR
  • positive CSF findings (pleocytosis, elevated protein level)
  • consider a combination of venous thrombosis and neuroinfection (in such instance, thrombosis is likely triggered by the infection)
  • typical symptoms and signs of IIH include
    • headache
    • abducens palsy
    • papilledema, visual disturbances (e.g., transient visual obscurations)
  • venous thrombosis should be excluded via MR venography (MRV) or CT venography (CTV)
  • lumbar puncture rules out infection and confirms elevated CSF pressure (through direct measurement of the opening pressure)
  • symptoms atypical for IIH:
    • encephalopathy
    • focal neurological deficits
    • seizures


  • common symptoms include headache, often severe and persistent, especially if worsening over time
  • other symptoms may include focal neurological deficits (such as visual disturbances), seizures, altered mental status, and other signs of intracranial hypertension
  • the clinical presentation can be varied and depends on the location and extent of thrombosis; a high index of suspicion is necessary, especially in patients with risk factors such as pregnancy, oral contraceptive use, prothrombotic conditions, or recent head injury
  • diagnosis is typically confirmed through imaging studies such as magnetic resonance imaging (MRI) or computed tomography (CT) venography, which can visualize the thrombosed veins and sinuses
  • MRI combined with MRV is the diagnostic imaging of choice for CVST as it provides detailed visualization of cerebral veins and sinuses and brain parenchyma
  • CTV is an alternative, especially when MRI is contraindicated or unavailable, but it is less sensitive in detecting acute thrombosis in smaller veins.
  • there is no specific laboratory test confirming the diagnosis
  • elevated D-dimer levels can suggest thrombosis, they are not specific for CVST and can be elevated in various conditions
  • normal D-dimer levels may help exclude CVST in patients with a low pre-test probability, but due to its limited sensitivity, a normal D-dimer level cannot definitively rule out CVST
  • lumbar puncture is not primarily used to diagnose CVST
  • it may be performed to analyze the cerebrospinal fluid (CSF) for signs of inflammation, infection or subarachnoid hemorrhage and to confirm increased intracranial pressure
  • proceed with caution due to the risk of herniation if significant mass effect is present
  • imaging may reveal absence of flow within affected veins or sinuses, filling defects representing thrombi, and signs of venous congestion such as engorgement of cortical veins or dilated deep veins
  • the “empty delta sign” on contrast-enhanced CT is a characteristic finding, representing a non-opacified thrombosed sinus surrounded by contrast
  • key radiological signs of CVST on MRI/MRV include the absence of flow void in the affected sinuses, the presence of a filling defect, and evidence of venous infarction or hemorrhage
  • transcranial Doppler ultrasound may be used to assess cerebral blood flow velocity and detect abnormal flow patterns suggestive of venous obstruction
  • however, it is less sensitive than imaging modalities such as MRI or CT venography and may not reliably visualize the thrombosed veins or sinuses
  • while clinical suspicion is important, the diagnosis typically requires confirmation through imaging studies
  • in rare cases where imaging is inconclusive, further evaluation with repeat imaging or digital subtraction angiography may be necessary
  • understanding the location and extent of CVST is fundamental for predicting clinical outcomes, guiding management strategies, assessing treatment response, and monitoring for potential complications
  • while anticoagulation is the cornerstone of treatment, extensive or strategically located thromboses (such as deep venous system) may warrant more aggressive interventions, including endovascular procedures or neurosurgical interventions

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