1.0 Clinical Presentation

1. i. Awareness of CVT as a possible differential diagnosis is an important part of maintaining an appropriate index of clinical suspicion. Front-line physicians and other healthcare professionals should receive education related to the clinical presentation and diagnosis of this condition [Strong recommendation; Low quality of evidence].

2. ii. In considering a diagnosis of CVT, healthcare professionals should consider both the individual’s symptoms and CVT risk factors [Strong recommendation; Moderate quality of evidence].

Refer to Table 1 – Common Clinical Features at the Time of Presentation with CVT

Refer to Figure 1 – Patient Characteristics, Risk Factors, and Conditions Associated with Cerebral Venous Thrombosis

1.1 Initial Clinical Assessment of Symptomatic CVT

1. i. Symptomatic CVT is a medical emergency. Individuals with confirmed or suspected CVT should receive urgent and appropriate neuroimaging and clinical evaluation [Strong recommendation; Low quality of evidence]. Refer to Section 1.2 for more information on imaging.

2. ii. Individuals with confirmed or suspected CVT should be assessed for ongoing clinical stability (airway, breathing, circulation), active seizures, and increased intracranial pressure including fundoscopy [Strong recommendation; Moderate quality of evidence].

1.2 Diagnosis of CVT and Other Investigations

1.2.1 Imaging Recommendations

1. i. Individuals with a suspected diagnosis of CVT should receive both parenchymal and neurovascular imaging (non-contrast CT and CT venography or MRI brain and MR venography as described in 1.2.1.ii) immediately following clinical stabilization to confirm diagnosis [Strong recommendation; Moderate quality of evidence].

2. ii. Individuals with a suspected diagnosis of CVT should undergo either contrast-enhanced CT venography or contrast-enhanced MR venography for diagnosis of CVT [Strong recommendation; Moderate quality of evidence].

   1. a. Isolated non-contrast CT head is not recommended as it is not sufficient to rule in or rule out a diagnosis of CVT [Strong recommendation; Moderate quality of evidence].

3. iii. Contrast-enhanced MR venography is recommended over time-of-flight MR venography due to the possibility of false positive diagnoses as a result of flow-related artifacts [Strong recommendation; Moderate quality of evidence].

   1. a. Time-of-flight MR venography without contrast is not recommended as it is insufficiently sensitive for the diagnosis of cortical vein thrombosis [Strong recommendation; Moderate quality of evidence].

   2. b. For individuals with a suspected diagnosis of isolated cortical vein thrombosis not confirmed with first-line imaging, additional imaging with MRI gradient echo or susceptibility-weighted imaging is recommended [Strong recommendation, Moderate quality of evidence].

1.2.2 Other Investigations

1. i. D-dimer measurement has limited diagnostic utility for the assessment of individuals with suspected CVT due to insufficient sensitivity to exclude cases where pre-test probability of a CVT diagnosis is lower. Using the results of D-dimer testing to determine whether neuroimaging should be performed in individuals with suspected CVT is not recommended [Strong recommendation; Moderate quality of evidence].

2. ii. Routine lumbar puncture is not recommended for the diagnosis of CVT [Strong recommendation; Very low quality of evidence].

3. iii. The following laboratory investigations should be routinely considered in individuals with CVT as part of the initial evaluation: hematology (complete blood count), electrolytes, coagulation (activated partial thromboplastin clotting time, International Normalized Ratio), renal function (creatinine, estimate glomerular filtration rate), random glucose, alanine transaminase, thyroid stimulating hormone, and beta human chorionic gonadotropin pregnancy test in individuals able to become pregnant [Strong recommendation; Low quality of evidence].

Section 1.2: Clinical Consideration

1. 1. Symptomatic CVT can be challenging to diagnose in the absence of appropriate clinical suspicion, and without appropriate neurovascular imaging.

Refer to Section 3.1 for additional laboratory tests related to hypercoagulability workup and recommended timing.

Refer to online supplemental information in Appendix One for other laboratory tests which may be considered in specific circumstances, depending on clinical presentation and risk profile; and Appendix Two for Antiphospholipid Antibody Testing in CVT flowsheet.

Notes

These recommendations refer to initial acute management of CVT. Outpatient management of CVT in the post-acute phase is discussed in Section 3.

Anticoagulation treatment: Anticoagulation management for CVT can be categorized into 3 phases: (1) acute management, which is immediately around the initial diagnosis; (2) “primary” management, which is the period of time when a person is treated with therapeutic anticoagulation for their initial CVT; (3) “secondary prevention,” which is any further antithrombotic therapy after the primary phase aimed at preventing VTE recurrence (ASH Guideline 2020).^{Reference Ortel, Neumann and Ageno48}

Symptomatic CVT - where the diagnosis is associated with neurological symptoms such as headache, focal neurological symptoms, seizure, or signs of increased intracranial pressure.

2.0 Stroke Unit Management

1. i. Individuals with a diagnosis of CVT requiring inpatient management should receive routine stroke unit care [Strong recommendation; High quality of evidence]. Refer to CSBPR Acute Stroke Management module, Section 8 for additional information.

2. ii. Individuals with CVT should receive supportive care with hydration, management of intracranial pressure, headache, nausea and vomiting, and seizures [Strong recommendations; Low quality of evidence]. Refer to Section 3 for additional information on late seizures and epilepsy and post-acute headaches. Refer CSBPR Acute Stroke Management module, Section 9 for additional information on post stroke complications and management.

2.1 Antithrombotic Management

1. i. Therapeutic-dose subcutaneous low-molecular-weight heparin (LMWH) or intravenous unfractionated heparin (UFH) should be initiated as soon as possible following diagnosis of symptomatic CVT [Strong recommendation; Moderate quality of evidence].

   1. a. Subcutaneous LMWH is preferred over intravenous UFH infusion for most individuals with CVT due to more reliable and longer duration of anticoagulant effect, predictable pharmacokinetics enabling administration of fixed doses without laboratory monitoring, and lower risk of heparin-induced thrombocytopenia [Conditional recommendation; Moderate quality of evidence]

   2. b. Intravenous UFH is typically reserved for individuals with CVT who have severely impaired renal function or require a surgical or invasive procedure [Conditional recommendation; Low quality of evidence].

   3. c. If using intravenous UFH, it should be administered as a bolus followed by infusion and adjusted based on institutional protocols [Conditional recommendation; Low quality of evidence].

   4. d. Heparin should be avoided in individuals with CVT with a history of heparin-induced thrombocytopenia (HIT) [Strong recommendation; Moderate quality of evidence].

   5. e. For any individuals with CVT with a history of HIT consider consulting hematology to discuss anticoagulant management [Strong recommendation; Low quality of evidence].

2. ii. There is currently insufficient evidence to recommend the routine use of direct oral anticoagulants (DOACs) as the initial antithrombotic of choice (i.e., without parenteral lead-in anticoagulation) in the acute management of CVT [Conditional recommendation; Low quality of evidence].

3. iii. The presence of intracranial or subarachnoid blood is not a contraindication to anticoagulation [Strong recommendation; Moderate quality of evidence].

4. iv. Systemic intravenous thrombolysis is not recommended in the acute treatment of CVT [Strong recommendation; Low quality of evidence].

Section 2.1 Clinical Considerations

1. 1. There may be rare cases where there are concerns regarding the safety of anticoagulation (e.g., large or rapidly expanding intracranial hemorrhage, anticipated emergency surgical intervention, meningitis/encephalitis with cortical venous hemorrhage) that will require case-by-case collaborative decision-making by neurology, neurosurgery and hematology/thrombosis. The benefits of anticoagulation should be weighed against the risks of symptomatic hemorrhage and should be regularly re-evaluated based on clinical and neuroimaging reassessment. If experts are not available on site, arrangements should be in place to contact the nearest center providing these services. Refer to Section 2.7 on “Surgical Management, Clinical Consideration 2” for additional information.

2. 2. The presence of concurrent head or neck infection is not an absolute contraindication to anticoagulation.

3. 3. There is insufficient evidence to support routine use of DOACs as first-line anticoagulation for CVT, although first-line DOAC may be considered on a case-by-case basis.

2.2 Inpatient Seizure Management

1. i. In individuals with CVT who have not had clinical seizures, use of prophylactic anti-seizure medications (ASMs) is not recommended [Strong recommendation; Low quality of evidence].

2. ii. Acute symptomatic seizure(s) (occurring within 7 days of presentation) requires management with ASMs per local protocols to prevent further acute symptomatic seizures [Strong recommendation; Low quality of evidence].

3. iii. Late seizures (occurring after 7 days of presentation), regardless of the presence or absence of acute symptomatic seizures, may require long-term management with ASMs [Strong recommendation; Moderate quality of evidence].

4. iv. Status epilepticus should be treated as per accepted local protocols [Strong recommendation; High quality of evidence].

5. v. Electroencephalography should be considered for individuals with episodic or prolonged unexpected alterations in level of consciousness to rule out non-convulsive seizures or status epilepticus [Strong recommendation; Low quality of evidence].

Section 2.2 Clinical Considerations

1. 1. The choice of ASMs will be dependent on individual factors including co-morbidities and interactions with other treatments including anticoagulation. The duration of treatment with ASMs will be person-dependent. Long-term management with ASMs (greater than 3 months) may not be required.

2.3 Acute Headache Management

Note, no evidence-based recommendations included for this section.

Section 2.3 Clinical Considerations:

1. 1. Headache from CVT is most commonly secondary to increased intracranial pressure or intracranial hemorrhage. Early treatment with anticoagulation to reduce venous hypertension may help with headache management.

2. 2. It is reasonable to treat headache secondary to increased intracranial pressure with acetazolamide.

3. 3. The use of prolonged nonsteroidal anti-inflammatory drugs for headache management while taking concurrent anticoagulation should be avoided given the risk of bleeding.

Refer to Section 3 for additional information on longer-term management of chronic headaches.

2.4 Vision

Section 2.4 Vision

1. i. Individuals with visual symptoms or signs of increased intracranial pressure (ICP) on the initial treating physician’s bedside examination should have an urgent ophthalmologic assessment, ideally within 24–48 hours of CVT diagnosis [Strong recommendation; Low quality of evidence].

Section 2.4 Clinical Considerations:

1. 1. All individuals with a new diagnosis of CVT should have an initial ophthalmological assessment including fundus examination and assessment for papilledema, visual fields and enlarged blind spots at the time of their diagnosis.

   1. a. Individuals with evidence of visual abnormalities or severe papilledema should receive an urgent ophthalmology assessment and be started on acetazolamide.

2. 2. Individuals without visual symptoms or signs of increased ICP should have an ophthalmologic assessment, ideally within 7 days of CVT diagnosis.

3. 3. Individuals without ophthalmic abnormalities related to the CVT on initial assessment should have a subsequent ophthalmologic assessment to rule out development of later-onset papilledema (as outlined above).

4. 4. The initial formal ophthalmological assessment should be performed by a neuro-ophthalmologist or ophthalmologist.

   1. a. If there are no ophthalmologists locally accessible, then an optometrist capable of performing a dilated fundus examination can perform the initial assessment with an ophthalmologist or neuro-ophthalmologist consulted remotely for advice.

5. 5. Ophthalmologic assessment should include:

   1. a. Best-corrected visual acuity and color vision

   2. b. Dilated fundus examination with stereoscopic viewing of the fundus.

   3. c. If papilledema is present, there should be automated threshold visual field testing with standard automated perimetry with white-on-white stimuli, which has the best evidence base for reliable, operator-independent longitudinal assessment of vision changes secondary to increased ICP. Papilledema can be graded using the modified Frisén scale for longitudinal follow-up.

6. 6. In the case of ophthalmologic diagnostic uncertainty as to whether there is papilledema secondary to increased intracranial pressure (vs. drusen, crowded discs, hyperopia), lumbar puncture with opening pressure and cerebrospinal fluid analysis should only be undertaken to clarify the presence of increased intracranial pressure if the benefits are deemed to outweigh the potential risks related to herniation and/or disrupting anticoagulation.

7. 7. Optimal timing for ophthalmologic reassessment is unclear; follow-up can be considered at 4 weeks and 3–6 months following diagnosis to exclude later-onset papilledema or vision loss.

2.4.1 Management of Papilledema

1. i. Acetazolamide may be initiated with dose escalation depending on the response of the papilledema to therapy. The risks of acetazolamide therapy, including fluid loss, metabolic acidosis, and hypokalemia, should be monitored, and individuals with CVT should be counseled to be aware of paresthesia as a common side effect with higher doses [Strong recommendation; Low quality of evidence].

2. ii. If, despite optimal medical management with anticoagulation and acetazolamide, there are either (1) worsening of visual field deficits, acuity, or color vision; or (2) severe visual field loss or abnormal acuity; then surgical intervention should be considered. The optimal approach (i.e. optic nerve sheath fenestration or cerebrospinal fluid diversion with shunting) can be considered as a shared decision with relevant experts (i.e. ophthalmologists, neurosurgeons) [Strong recommendation; Low quality of evidence].

Section 2.4.1 Clinical Considerations:

1. 1. Individuals with papilledema or visual symptoms that could be attributed to increased intracranial pressure should be managed by a neuro-ophthalmologist or ophthalmologist.

2.5 Neurocritical Care Management for CVT

1. i. Individuals with CVT should be routinely and regularly monitored clinically for signs or symptoms of increased intracranial pressure [Strong recommendation; Low quality of evidence].

2. ii. Individuals with CVT identified to have elevated ICP should be treated emergently based on the severity of signs and symptoms using standard protocols [Strong recommendation; Low quality of evidence].

   1. a. Those who fail medical management for elevated ICP and are at risk of life-threatening increased ICP should be considered for surgical and/or endovascular management, as appropriate [Strong recommendation; Low quality of evidence]. Please refer to Endovascular (Section 2.6) and Surgical management (Section 2.7) sections for additional information.

Section 2.5 Clinical Considerations:

1. 1. For signs and symptoms of ICP elevation, acetazolamide could be considered.

2. 2. Appropriate referrals to critical care and neurosurgical services should be considered for management of worsening ICP.

3. 3. Noninvasive or invasive ICP monitoring technologies can be considered in comatose patients.

2.6 Endovascular Management

1. i. Endovascular therapy should not be routinely used as first-line therapy for the acute treatment of cerebral venous thrombosis [Conditional recommendation; Moderate quality of evidence].

Section 2.6 Clinical Considerations

1. 1. The optimal candidates for endovascular therapy (EVT) for CVT are not known.

2. 2. The optimal technical approaches for endovascular therapy for CVT, if any, are not known, and the procedure should be performed by an experienced neurointerventionalist.

3. 3. The optimal timing for EVT, if any, is not known.

   1. a. Endovascular therapy (EVT) may be considered for treatment of cerebral venous thrombosis in cases where there is clinical deterioration despite optimal medical therapy and mechanical recanalization is considered to be of potential benefit.

   2. b. In select cases where the treating physician and neurointerventionalist agree that the benefits of early intervention are highly likely to exceed potential risks, EVT may be considered alongside anticoagulation as first-line therapy for the acute treatment of CVT.

4. 4. EVT should be considered as a complement, and not a substitute, to anticoagulation unless anticoagulation is otherwise contraindicated (e.g., active and uncontrolled bleeding).

2.7 Surgical Management

1. i. Decompressive hemicraniectomy should be considered in cases of life-threatening malignant mass effect due to venous infarction and/or hemorrhage [Strong recommendation; Moderate quality of evidence].

Section 2.7 Clinical Considerations:

1. 1. Insertion of an external ventricular drain can be considered as a treatment and/or monitoring option for elevated ICP and/or hydrocephalus.

2. 2. If anticoagulation must be disrupted for a neurosurgical procedure, the approach to restarting anticoagulation should be made on a case-by-case basis in discussion with a neurosurgeon and with review of repeat neuroimaging with relevant specialists involved (e.g., stroke neurology, hematology).

3. 3. Long-term management of chronically elevated ICP may require surgical management including insertion of a shunt (ventriculoperitoneal or lumboperitoneal); or optic nerve sheath fenestration.

3.1 Factors Related to Clinical Decision-Making for Anticoagulation

1. i. Vitamin K antagonists (dose-adjusted to target INR 2.0–3.0) and/or DOACs are suitable options for oral anticoagulation for individuals with CVT. [Strong recommendation; Moderate quality of evidence].

2. ii. Vitamin K antagonists are the preferred standard of care for individuals with a confirmed diagnosis of antiphospholipid antibody syndrome, and always for those with triple antiphospholipid antibody positivity. [Strong recommendation; Moderate quality of evidence].

Section 3.1 Clinical Considerations

1. 1. Unless there is a clear indication for ongoing parenteral anticoagulation (e.g., pregnancy), individuals with CVT should be transitioned to an oral anticoagulant for primary treatment once clinically stable.

2. 2. Anticoagulation should be continued for a minimum of 3 months. The optimal duration of primary anticoagulation is not known. The net clinical benefit of long-term anticoagulation for secondary prevention of idiopathic CVT after initial 3 to 12 months of primary treatment is also not known.

3. 3. In making decisions around duration of anticoagulation, individuals with CVT can be stratified according to the presence or absence of transient and chronic thrombotic risk factors, as well as other factors known to be associated with recurrent CVT and/or VTE (e.g., unprovoked event, male sex), which influence the risk of recurrence after discontinuation of anticoagulation.

   1. a. Individuals with CVT associated with a major transient risk factor (e.g., isolated oral contraceptive use, early post-partum period) should receive primary anticoagulation treatment for at least 3 to 6 months. Refer to CVT and Pregnancy (Section 4) for additional information on thromboprophylaxis.

   2. b. Individuals with a first episode of CVT without a prior history of VTE, or other identifiable risk factors, should receive primary anticoagulation treatment for 6 to 12 months. Decisions regarding further extension of anticoagulation for secondary prevention should be based on the estimated risk of recurrent CVT and/or VTE and bleeding, and with shared clinical decision-making in conjunction with the individual and with thrombosis expertise when necessary.

   3. c. Individuals with a major chronic thrombotic risk factor (e.g., active cancer), recurrent CVT, recurrent VTE, or high-risk thrombophilia (antiphospholipid antibody syndrome, homozygous factor V Leiden, homozygous prothrombin gene mutation, combination inherited thrombophilia, deficiencies of natural anticoagulants [protein C, protein S, antithrombin]) should be considered for indefinite anticoagulation, without disruption between the primary treatment and secondary prevention phases of therapy. Consider consultation with a clinician with thrombosis expertise for ongoing management.

4. 4. Recommendations for ongoing antithrombotic therapy for secondary prevention and choice of agent should be made on a case-by-case basis based on the estimated risk of recurrent CVT and/or VTE and bleeding, and with shared clinical decision-making in conjunction with the individual with CVT and with thrombosis expertise when necessary.

3.1.1 CVT Workup: Cancer Screening and Hypercoagulability Testing

1. i. Individuals with CVT should be assessed for additional risk factors for CVT and managed as per usual care, including ensuring guideline-recommended age-appropriate cancer screening is up to date. [Strong recommendation; Moderate quality of evidence].

3.1.2 Inherited Thrombophilia

Note, no evidence-based recommendations included for this section.

Section 3.1.2 Clinical Considerations

1. 1. Limited observational data suggest that inherited thrombophilia may increase the risk of VTE recurrence after CVT.

   1. a. Testing for inherited thrombophilia and the spectrum of thrombophilia workup is an area of ongoing controversy, as is decision-making around testing.

   2. b. Current guidelines from the International Society on Thrombosis and Hemostasis recommend testing for inherited thrombophilia in individuals with CVT who would otherwise not have an indication for indefinite anticoagulation.

2. 2. Screening for inherited thrombophilia should include testing for antithrombin-3, protein C, and protein S deficiencies, factor V Leiden, and prothrombin gene mutation (G20210A) according to ISLH guidelines.^{Reference Marlar, Gausman and Tsuda73,Reference Barbhaiya, Zuily and Naden74}

   1. a. Levels of antithrombin, protein C and protein S can be affected by acute thrombosis, anticoagulation, and pregnancy/puerperium. Therefore, testing is not recommended in the acute setting (based on ISLH guidelines), and rather when making the decision as to if or when to transition to anticoagulation for secondary prevention.

3. 3. Consultation with hematology/thrombosis should be considered for guidance regarding the appropriateness, timing and interpretation of testing.

3.1.3 Antiphospholipid Antibody Syndrome (APS)

1. i. Individuals with CVT without a known history of antiphospholipid antibody syndrome should be tested for antiphospholipid antibodies as it may influence antithrombotic decision-making (choice of antithrombotic agent or duration of treatment) [Strong recommendation; Low quality of evidence]. Refer to Online Supplement, Appendix Two for additional information.

   1. a. As per the 2023 American College of Rheumatology/European Alliance of Associations for Rheumatology criteria, an individual must meet required clinical and laboratory criteria for a diagnosis of APS. Testing includes measurement of nonspecific inhibitor (lupus anticoagulant), anticardiolipin antibody, and anti-beta2 glycoprotein-I antibody according to guidelines [Strong recommendation; Low quality of evidence].^{Reference Marlar, Gausman and Tsuda73,Reference Tripodi, Cohen and Devreese75–Reference Baker, Platton and Gibson77}

   2. b. Testing for a nonspecific inhibitor (lupus anticoagulant) should be conducted prior to initiation of anticoagulation, which interferes with the results of testing. Anticoagulation should not be delayed pending testing [Strong recommendation; Low quality of evidence].

3.2 Role of Routine Follow-up Vascular Neuroimaging

Section 3.2 Follow-Up Neurovascular Imaging

1. i. Routine follow-up vascular neuroimaging should be repeated within 3 to 6 months after initiating anticoagulation [Strong recommendation; Low quality of evidence].

Section 3.2 Clinical Considerations

1. 1. The ideal timing of follow-up vascular neuroimaging is uncertain.

2. 2. Although the role of late venous recanalization in predicting outcomes or guiding anticoagulation strategy is uncertain, repeat neuroimaging allows the treating clinician to visualize changes in thrombus burden over time and to establish a newer baseline if there are additional concerns about recurrent thrombosis in the future.

3. 3. Ideally, repeat vascular neuroimaging should be performed with either CT or MRI contrast-enhanced vascular imaging.

4. 4. Beyond six months of treatment, the role of routine subsequent vascular neuroimaging is uncertain but can be considered if it will change antithrombotic treatment considerations (i.e., duration of treatment).

5. 5. In the clinically stable individual with CVT who has completed primary treatment with anticoagulation, with no recurrent symptoms and recanalization of a chronic stable thrombus, the role of ongoing surveillance with vascular neuroimaging is unlikely to be of benefit.

6. 6. There is no indication for routine surveillance imaging after CVT in asymptomatic individuals to rule out development of dural arteriovenous fistula.

7. 7. Choice of modality for repeat neuroimaging (i.e., CT vs MR), particularly in instances where there will be multiple follow-ups, should be considered in the context of resources (i.e., availability and wait-lists) as well as risks of repeat radiation exposure, particularly in younger individuals.

3.3 Management of Other Post-acute Sequelae of Cerebral Venous Thrombosis

3.3.1 Post-CVT Management

Note, individuals with CVT tend to be younger than other individuals with lived experience of stroke. Their post-CVT care needs are unique, less studied and will vary depending on their individual work, school and home situations. Cognitive complaints, headaches and fatigue may be significantly disabling without radiologic evidence of residual CVT sequalae. Some basic principles do apply to all individuals post CVT.

1. i. All individuals with CVT should be assessed for mood, cognition, fatigue, functional impairments (including visual deficits), headache and rehabilitation needs at the time of their event and throughout their recovery [Strong recommendation; Low quality of evidence].

2. ii. All individuals with CVT with functional impairments and rehabilitation goals should undergo early rehabilitation as per Canadian Stroke Best Practice Recommendations [Strong recommendation; Moderate quality of evidence]. Refer to CSBPR Rehabilitation, Recovery and Community Participation Following Stroke for additional information. ^{Reference Teasell, Salbach and Foley78}

3. iii. Individuals with mood disturbance following CVT should be treated and referred to appropriate mental health support services [Strong recommendation; Moderate quality of evidence].

4. iv. Individuals with post-CVT fatigue should be assessed for reversible causes and be advised on pharmacologic and non-pharmacologic strategies for management [Strong recommendation; Low quality of evidence].

5. v. Individuals with CVT with cognitive concerns should be screened with validated screening tools [Strong recommendation; Low quality of evidence]. Refer to CSBPR Vascular Cognitive Impairment module for additional information. ^{Reference Lanctôt, Lindsay and Smith79}

   1. a. Further neuropsychological evaluation is recommended if impairments are identified on screening, or the individual continues to have subjective cognitive complaints which are interfering with their daily functioning. This is especially important in individuals who are still working or in school, to establish the degree and severity of deficits, in order to inform return to work and school, and to determine what accommodations can be made [Strong recommendation; Low quality of evidence].

6. vi. Individuals with CVT should be assessed for return to work or school at follow-up and throughout transitions of care [Strong recommendation; Low quality of evidence]. Refer to CSBPR Rehabilitation, Recovery and Community Participation Following Stroke for additional information.^{Reference Mountain, Patrice Lindsay and Teasell80}

7. vii. Individuals with CVT with residual impairments and/or seizures should be assessed for return to driving when appropriate. Recommendations for return to driving should be guided by provincial licensing requirements [Strong recommendation; Low quality of evidence]. Refer to CSBPR Rehabilitation, Recovery and Community Participation Following Stroke ^{Reference Teasell, Salbach and Foley78}

8. viii. Individuals with lived experience of CVT should be advised about what is known regarding the natural history of post-CVT sequalae and should be made aware of peer support groups [Strong recommendation; Low quality of evidence].

3.3.2 Late Seizures and Epilepsy

1. i. Individuals with CVT who develop late seizures (>7 days post-diagnosis) should be treated with appropriate ASM per standard guidelines [Strong recommendation; Moderate quality of evidence].

2. ii. Most late post-CVT seizures will be associated with an elevated risk of recurrent seizures (epilepsy) related to chronic structural lesions (e.g. encephalomalacia). This will likely require long-term management with ASM, which is to be reviewed as part of routine clinical follow-up [Strong recommendation; Moderate quality of evidence].

Section 3.3 Clinical Considerations

Post-Acute Symptoms

1. 1. Individuals with CVT with an adverse change in headache pattern, worsening seizures, new focal deficits, visual symptoms, or pulsatile tinnitus following initial CVT should be evaluated clinically and with repeat parenchymal and vascular neuroimaging to exclude complications including CVT recurrence, intracranial hypertension or dural arteriovenous fistula.

2. 2. After the acute phase, individuals with CVT who continue to experience headaches should be assessed and treated according to chronic headache management principles. If after standard management, the individual with CVT continues to have persistent and debilitating headaches, consider referral to a practitioner with expertise in treatment of headaches.

4.1 Cerebral Venous Thrombosis and Pregnancy

1. i. A history of CVT is not a contraindication to pregnancy [Strong recommendation; Moderate quality of evidence].

2. ii. Individuals with a history of CVT who are not receiving long-term anticoagulation, and, who become pregnant, should receive prophylactic low-dose thromboprophylaxis with low-molecular-weight heparin during their pregnancy and during the first six weeks postpartum, and should receive an assessment by a thrombosis specialist and/or obstetric medicine specialist [Strong recommendation; Moderate quality of evidence].

3. iii. Individuals who develop CVT during pregnancy should be anticoagulated with therapeutic Low Molecular Weight Heparin and receive follow-up by a Thrombosis and/or Obstetric Medicine specialist during their pregnancy [Strong recommendation; Moderate quality of evidence].

   1. a. A thrombosis specialist and/or obstetric medicine specialist should also be involved in anticoagulation management around the time of delivery [Conditional recommendation; Low quality of evidence].

4. iv. Direct oral anticoagulants (DOACs) and warfarin should not be used for anticoagulation in individuals who are pregnant [Strong recommendation; Low quality of evidence].

5. v. DOACs should not be used in individuals who are breastfeeding [Strong recommendation; Low quality of evidence].

Refer to CSBPR Acute Stroke Management during Pregnancy module for additional information. ^{Reference Ladhani, Swartz and Foley92}

Section 4.1 Clinical Considerations

4.1.1 CVT and Pregnancy

1. 1. There is uncertainty regarding the optimal mode of delivery in pregnant women with CVT. Discussion among the clinical team including neurology and obstetrics is recommended.

4.1.2 Anticoagulation and heavy menstrual bleeding

1. 1. Individuals who menstruate who are initiating anticoagulation should be counseled around the possibility of heavy menstrual bleeding on anticoagulation and should be referred to a thrombosis specialist if this issue arises.

2. 2. Referral to gynecology should be made for definitive management of heavy menstrual bleeding or any post-menopausal vaginal bleeding on anticoagulation.

3. 3. Use or continuation of OCP is acceptably safe if the individual is being concurrently anticoagulated. However, OCP should be discontinued if anticoagulation is discontinued.

4. 4. Individuals with a history of CVT should be counseled to be vigilant for venous thromboembolism symptoms and should be assessed for thromboprophylaxis for venous thromboembolism during higher-risk scenarios (e.g., hospitalization, post-operative).

5.1 Trauma-Associated CVT

Note, no evidence-based recommendations included for this section.

Section 5.1 Clinical Considerations

1. 1. The antithrombotic management of individuals with CVT in the context of major head trauma should be managed with multidisciplinary expertise on a case-by-case basis. Management decisions may evolve over time and should incorporate clinical reassessment, when possible, and repeat neuroimaging.

2. 2. The need for anticoagulation should be assessed in the context of whether the CVT is clinically symptomatic, demonstrates extension on follow-up vascular neuroimaging, and/or is associated with signs of parenchymal changes independently attributable to the CVT (i.e., venous edema/infarction, venous hemorrhage), as opposed to from an evolving traumatic brain injury.

3. 3. The benefits of anticoagulation and dosing should be weighed against risks of intracranial or extracranial hemorrhage related to the traumatic brain injury and/or other extracranial injuries.

5.2 Incidentally Diagnosed Cerebral Venous Thrombosis

Note, no evidence-based recommendations included for this section.

Section 5.2 Clinical Considerations

1. 1. The clinical relevance of incidentally detected CVT in the context of vascular neuroimaging performed for other indications is not known. Indications for hypercoagulable testing should be the same as in symptomatic CVT.

2. 2. Individuals with incidentally diagnosed CVT should be referred for routine thrombosis and ophthalmology assessments.

3. 3. Suitability for primary anticoagulation and secondary prevention should be considered on a case-by-case basis in clinical and radiologic context.

4. 4. It should be noted that dural arteriovenous fistula is associated with CVT and definitive investigations and management are outside the scope of this guideline. Individuals with dural arteriovenous fistula without definite preceding history of CVT should be evaluated by a multidisciplinary team to determine if there is any clinical suspicion of preceding history of CVT which will guide further investigations and management.

5.3 COVID-19-associated Cerebral Venous Thrombosis

Note, no evidence-based recommendations included for this section.

Section 5.3 Clinical Considerations

1. 1. Severe acute respiratory syndrome coronavirus 2 (COVID-19) infection may be associated with an increased risk of CVT. CVT in the context of COVID-19 infection should not be managed differently than other cases of CVT. All recommendations and consensus statements in this module should be applied where appropriate.

2. 2. Testing for COVID-19 infection in the context of CVT should be performed as per local protocols.

3. 3. For individuals with CVT who have an indication for ritonavir, the treating physician should be aware of a potential drug-drug interaction with DOACs with increased anticoagulant effect. An individualized approach should be considered in adjusting management.

5.4 Vaccinations and Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT) - Associated CVT

Note, no evidence-based recommendations included for this section.

Section 5.4 Clinical Considerations

1. 1. A history of CVT is not a contraindication to receiving mRNA vaccinations against COVID-19 or vaccinations against other diseases. Anticoagulant therapy is not a contraindication to receiving vaccinations. Application of prolonged pressure at the injection site following vaccination is recommended to reduce bruising.

2. 2. VITT as the cause of CVT is extremely rare. Cases should only be considered in the specific context of recent adenovirus vector-based COVID-19 vaccination (AstraZeneca/Oxford ChadOx1 nCov-19 or Janssen/Johnson & Johnson Ad26.COV2.S).

3. 3. Diagnostic criteria for VITT have varied depending on timing of publication, concurrent state of knowledge, and local clinical environment. Common elements of most diagnostic criteria include elevated D-dimer, reduced fibrinogen, positive anti-Platelet Factor 4-antibodies by enzyme-linked immunosorbent assay testing, thrombocytopenia and onset of symptoms after 4 days of adenovirus vector-based COVID-19 vaccination. Diagnosis as per local protocols is advised.

4. 4. Management of VITT-associated CVT is distinct from other types of CVT. Treatment guidelines have been published by several national and international societies and generally involve use of high-dose intravenous immunoglobulin, use of non-heparin anticoagulation, and avoidance of platelet transfusions unless there is life-threatening bleeding or immediate major surgery is indicated.

5. 5. In cases of CVT where VITT is a potential consideration, expert thrombosis consultation should be sought immediately and prior to the initiation of therapy. Transfer to an EVT-capable center should also be considered.