Duration of Aspirin Therapy for Vertebral Artery Dissection
Continue aspirin therapy for at least 3 months after vertebral artery dissection, then transition to indefinite single antiplatelet therapy for secondary stroke prevention. 1
Initial Treatment Period: 3 Months Minimum
The 2021 AHA/ASA Stroke Prevention Guidelines establish that antithrombotic therapy for at least 3 months is indicated for patients with ischemic stroke or TIA after extracranial vertebral artery dissection to prevent recurrent stroke or TIA. 1 This represents a Class I, Level C-EO recommendation—the strongest level of guidance based on expert consensus. 1
Either aspirin or anticoagulation can be used during this initial 3-month period, as the CADISS trial demonstrated no significant difference in stroke or death rates between antiplatelet therapy (2% recurrence) versus anticoagulation (1% recurrence) at 1 year follow-up (OR 0.56,95% CI 0.10-3.21). 1, 2 The 2023 World Stroke Organization synthesis confirms this equipoise, stating that either antiplatelet therapy or oral anticoagulants are recommended for at least 3 months. 1
Optimal Aspirin Dosing Strategy
Use aspirin 75-100 mg daily for maintenance therapy after the acute phase. 1, 3 The 2015 Canadian Stroke Best Practice Recommendations specify that ASA 81-325 mg daily should be continued indefinitely or until an alternative antithrombotic regimen is started. 1 However, lower doses (75-100 mg) are preferred for long-term use as they provide equivalent cardiovascular protection with reduced bleeding risk. 3
For the acute loading phase, administer at least 160 mg of aspirin immediately after brain imaging excludes intracranial hemorrhage. 1
Transition to Long-Term Therapy After 3 Months
After completing the initial 3-month treatment period, continue single antiplatelet therapy indefinitely for secondary stroke prevention. 1 The rationale is that vertebral artery dissection causes stroke primarily through artery-to-artery embolism from intraluminal thrombus, and most dissections heal spontaneously within 3 months. 1
The Canadian guidelines explicitly state that ASA should be "continued indefinitely or until an alternative antithrombotic regime is started" after the acute phase. 1 This aligns with the World Stroke Organization recommendation that antiplatelet agents are indicated for secondary stroke prevention in patients with non-cardioembolic ischemic events. 1
Special Considerations for Your Patient
The hypertensive emergency context does not change the dissection treatment duration, but aggressive blood pressure control becomes critical for long-term management. 1 The dissection itself—not the hypertensive emergency—determines the antithrombotic strategy.
Monitor for dissection healing at 3 months with vascular imaging (CTA or MRA) to confirm resolution or stabilization. 1 If the dissection has healed and no other high-risk features are present, continue aspirin 75-100 mg daily as standard secondary stroke prevention. 1, 3
Evidence Supporting Low Recurrence Risk
The actual risk of recurrent stroke after vertebral artery dissection is remarkably low when treated with antithrombotic therapy. A 21-year retrospective study of 110 VAD patients found only one recurrent ischemic event during follow-up, with no difference between aspirin and anticoagulation groups. 4 Similarly, a larger study of 370 patients with carotid and vertebral dissections showed new or recurrent events in only 9.6% on antiplatelets versus 10.4% on anticoagulation—a non-significant difference. 5
The CADISS trial confirmed this low recurrence rate in a randomized setting, with only 2.5% experiencing recurrent stroke at 1 year. 2 This evidence supports the safety of aspirin monotherapy after the initial 3-month period.
Critical Pitfalls to Avoid
Do not discontinue aspirin after 3 months—this is when you transition from "dissection-specific" treatment to "secondary stroke prevention" treatment, not when you stop therapy entirely. 1 The 3-month mark represents the minimum duration for addressing the acute dissection, but lifelong antiplatelet therapy is required for stroke prevention. 1
Do not use aspirin doses above 325 mg for maintenance therapy, as higher doses increase bleeding risk without additional cardiovascular benefit. 3 The optimal maintenance dose is 75-100 mg daily. 1, 3
Do not combine antiplatelet therapy with anticoagulation unless there is a separate indication (such as atrial fibrillation), as combined therapy showed higher event rates (13.3-20%) compared to monotherapy in dissection patients. 5
Monitoring Strategy
Reassess at 3 months with clinical evaluation and vascular imaging to confirm dissection healing. 1 If imaging shows persistent pseudoaneurysm or progressive arterial complications despite antithrombotic therapy, consider consultation for potential endovascular intervention. 1
Continue aspirin 75-100 mg daily indefinitely as long as no contraindications develop (such as major bleeding requiring discontinuation). 1, 3 Annual follow-up should assess medication adherence, bleeding complications, and cardiovascular risk factor control. 3