Cerebral venous thrombosis
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Cerebral Venous Thrombosis (CVT)
Overview
CVT is an uncommon but serious cerebrovascular disorder, accounting for 0.5%-3% of all strokes. It predominantly affects young adults (mean age ~40 years), with 80% of cases presenting before age 50. Women are affected three times more often than men, largely due to pregnancy/puerperium and oral contraceptive use. The increasing recognition of CVT reflects improved clinical awareness and widespread use of MRI/MR venography.
- Bradley and Daroff's Neurology in Clinical Practice
- Tintinalli's Emergency Medicine
Anatomy
The cerebral venous system consists of dural venous sinuses (superior sagittal sinus, transverse sinuses, sigmoid sinuses, cavernous sinuses) and cortical/deep cerebral veins. The superior sagittal sinus is the most frequently involved site in CVT. Deep venous thrombosis can involve the internal cerebral veins and the vein of Galen.
Pathophysiology
Two main mechanisms lead to brain injury in CVT:
- Venous obstruction - impaired venous drainage raises venous and capillary pressure. Cerebral venous anastomoses can partially compensate, but when overwhelmed, the blood-brain barrier disrupts, cerebral perfusion pressure falls, and cerebral edema, infarction, and hemorrhage result.
- CSF outflow obstruction - thrombosis of the superior sagittal sinus (the main site of arachnoid granulations) impairs CSF resorption, causing intracranial hypertension.
Venous infarctions are typically multifocal, bilateral, involve both gray and white matter, and are often hemorrhagic (in nearly 40-50% of cases). They do not respect arterial territory boundaries.
- Tintinalli's Emergency Medicine
Etiology and Risk Factors
At least one risk factor is identified in 85% of patients; multiple risk factors in ~50%.
| Category | Examples |
|---|---|
| Thrombophilia | Factor V Leiden, prothrombin G20210A mutation, protein C/S deficiency, antithrombin III deficiency, antiphospholipid syndrome |
| Hormonal/Reproductive | Pregnancy, puerperium (especially days 7-14 postpartum), oral contraceptives |
| Infection | Otitis media/mastoiditis (lateral sinus), facial/orbital infection (cavernous sinus), skull osteomyelitis |
| Inflammatory disease | Behcet's disease, vasculitis, inflammatory bowel disease, SLE |
| Malignancy | Disseminated cancer, hematologic malignancies |
| Other | Dehydration, head trauma, recent lumbar puncture or neurosurgical procedures, sickle cell disease, SARS-CoV-2 infection |
No identifiable cause is found in approximately 15-20% of cases. Geographic variation is striking: India reports ~400-500 per 100,000 births for puerperal CVT (primarily from dehydration in home deliveries), versus ~9 per 100,000 in the United States.
- Bradley and Daroff's Neurology in Clinical Practice; Grainger & Allison's Diagnostic Radiology
Clinical Presentations
CVT produces four major overlapping syndromes:
| Syndrome | Features | Frequency |
|---|---|---|
| Isolated intracranial hypertension | Persistent/worsening headache, papilledema, decreased visual acuity | Most common |
| Focal neurological deficits | Motor weakness (may be bilateral), aphasia, sensory changes | ~30-40% |
| Seizures | Focal, generalized, or status epilepticus | ~30-40% |
| Encephalopathy | Confusion, altered mental status, coma | Less common, severe cases |
Key clinical features:
- Headache is the most common symptom and can be gradual or thunderclap (mimicking subarachnoid hemorrhage). It typically worsens with Valsalva maneuver.
- Superior sagittal sinus thrombosis causes bilateral leg weakness/sensory changes.
- Cavernous sinus thrombosis (usually septic) presents with proptosis, chemosis, and painful ophthalmoplegia.
- Lateral (transverse) sinus thrombosis (often from otitis media) causes headache, otalgia, fever, papilledema, and abducens palsy.
- Symptoms may be acute, subacute, or chronic in onset.
CVT should be high on the differential for young women presenting with stroke without conventional risk factors, unexplained new seizures, or refractory headaches.
- Tintinalli's Emergency Medicine; Rosen's Emergency Medicine
Diagnosis
Neuroimaging
MRI + MR venography (MRV) is the gold standard.
CT findings:
- "Cord sign": hyperdense clot in a cortical vein on non-contrast CT
- "Empty delta sign": filling defect within the superior sagittal sinus on contrast CT (posterior triangle of sinus enhances while the thrombus appears dark)
- Indirect signs: sulcal effacement, decreased grey/white matter differentiation
- Non-contrast CT may be completely normal
MRI findings:
- Loss of the normal flow void in a sinus
- Thrombus appears hyperintense on both T1 and T2 (subacute phase)
- Very acute thrombus can appear hypointense on T2 (risk of misdiagnosis as flow void)
- On SWI: "blooming" artifact from thrombus; prominent serpiginous veins indicating venous congestion
- Parenchymal edema: high T2/FLAIR signal; hemorrhagic transformation is common
MRV: Loss of flow signal, irregularity, or severe narrowing indicates thrombosis. Phase contrast technique with low-velocity encoding is used. Distinguishing thrombosis from a hypoplastic sinus or slow flow can be difficult.
CT venography has 75-100% sensitivity depending on anatomic location and is a reliable alternative to MRV (useful when MRI is unavailable).
Below is an MR venogram demonstrating absent flow in the right transverse and sigmoid sinuses (arrowhead) with intact left-sided flow (arrows):
Laboratory
- D-dimer: A normal D-dimer has a negative predictive value of ~99% for CVT, but a negative result should not solely exclude the diagnosis in high-risk patients.
- Thrombophilia screening: Protein C, protein S, antithrombin III activity, factor V Leiden, prothrombin G20210A, antiphospholipid antibodies. Test 2-4 weeks after completing anticoagulation (to avoid false-positive protein C/S results).
- CSF analysis: may help exclude meningitis/encephalitis; elevated opening pressure supports intracranial hypertension.
Treatment
Anticoagulation (cornerstone of therapy)
- Immediate anticoagulation is recommended even in the presence of intracranial hemorrhage - this counterintuitive recommendation is supported by evidence showing net benefit.
- LMWH (weight-adjusted subcutaneous) is preferred over unfractionated heparin (UFH) based on better outcomes and fewer hemorrhagic complications.
- Transition to warfarin (INR 2.0-3.0) after stabilization; duration typically at least 3 months, with longer therapy depending on the etiology and ongoing thrombophilic risk.
- DOACs: The 2024 AHA Scientific Statement notes that evidence for DOACs (rivaroxaban, dabigatran) vs. warfarin remains limited and inconclusive, though data in children suggests comparable efficacy to warfarin. DOACs should not replace standard therapy in most adult cases without further evidence.
Intracranial Pressure Management
- No strong evidence supports routine acetazolamide or corticosteroids for CVT-related ICP elevation.
- Measures to control ICP (head positioning, osmotic therapy) are used on a case-by-case basis.
Seizure Management
- Short-term antiepileptic drugs (AEDs) are recommended for supratentorial lesion patients who have had seizures to prevent early recurrent seizures.
- No evidence supports long-term prophylactic AEDs.
Endovascular Therapy
- Endovascular mechanical thrombectomy (EMT) or local thrombolytic infusion may be considered for severe or deteriorating cases despite maximal anticoagulation.
- A small trial found no benefit of endovascular therapy over medical therapy alone for average cases - reserve for refractory/severe disease.
Surgery
- Decompressive craniectomy may be required in selected cases with large hemorrhagic infarction and impending herniation.
- Septic CVT requires antibiotics targeting the underlying infection source.
Prognosis
- Overall mortality: approximately 10% from all causes.
- Death or dependence despite treatment: 10-15% of patients (2024 AHA statement).
- CVT associated with pregnancy/puerperium carries a more benign prognosis than non-pregnancy-associated CVT (Mexican cohort: 10% vs. 33% mortality).
- Peripartum CVT in the United States has demonstrated no deaths in a national survey of 4,454 patients.
Key Teaching Points
- CVT is easily overlooked - maintain high suspicion in young women with headache, seizures, or focal deficits without classical stroke risk factors.
- Non-contrast CT is often normal - MRI/MRV is mandatory if CVT is suspected.
- Anticoagulate even with hemorrhage on imaging.
- Screen all patients for thrombophilia (after completing anticoagulation).
- The 2024 AHA Scientific Statement provides an updated algorithm for management and guidance on progressive neurological deterioration.
Key References:
- Bradley and Daroff's Neurology in Clinical Practice, 8th ed.
- Tintinalli's Emergency Medicine, 9th ed.
- Rosen's Emergency Medicine, 10th ed.
- Goldman-Cecil Medicine, International Ed.
- Grainger & Allison's Diagnostic Radiology
- Saposnik et al., 2024 AHA Scientific Statement - Stroke (PMID: 38284265) - provides the most current management algorithm for CVT
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