Why is vertebral artery dissection treated with Aspirin (acetylsalicylic acid) and Plavix (clopidogrel) as if it were a stroke?

Why Vertebral Artery Dissection is Treated with Antiplatelet Therapy

Vertebral artery dissection is treated with antiplatelet agents (aspirin and/or clopidogrel) because the primary mechanism of stroke is artery-to-artery embolism from intraluminal thrombus formation, not the hemorrhagic dissection itself within the arterial wall. 1

The Pathophysiology Drives Treatment Choice

The key to understanding this treatment approach is recognizing that while dissection is a hemorrhagic process within the arterial wall, stroke occurs through a thrombotic mechanism:

• Artery-to-artery embolism is the dominant mechanism causing cerebral ischemia in vertebral artery dissection, accounting for stroke in 50-95% of cases 1
• The dissection creates an intraluminal thrombus that serves as an embolic source 1
• Hemodynamic compromise from vessel narrowing is a less common mechanism 1
• This embolic pathophysiology provides the rationale for antithrombotic therapy to prevent stroke 1

Guideline-Recommended Treatment Approach

First-Line Antithrombotic Therapy

For patients with ischemic stroke or TIA after vertebral artery dissection, antithrombotic therapy for at least 3 months is indicated (Class I recommendation). 1

The specific regimen options include:

• Either antiplatelet therapy OR anticoagulation is reasonable for the first 3 months, as they have equivalent efficacy 1
• Antiplatelet options: aspirin 50-325 mg daily or clopidogrel 75 mg daily 1
• Anticoagulation option: heparin followed by warfarin (INR 2.0-3.0) 1

The Evidence Supporting Equipoise

The landmark CADISS trial definitively established that antiplatelet and anticoagulation therapies are equivalent:

• 250 patients randomized within 7 days of symptom onset 2, 3
• Stroke or death occurred in 2% of antiplatelet patients vs 1% of anticoagulation patients (not statistically significant, p=0.63) 1, 2
• At 1-year follow-up: 3.2% events with antiplatelets vs 1.6% with anticoagulation (p=0.51) 1
• Most importantly, the overall recurrent stroke rate was remarkably low at only 2-2.5%, much lower than previously reported in observational studies 3

Why Dual Antiplatelet Therapy (Aspirin + Clopidogrel)?

While the question specifically asks about aspirin and Plavix together, guidelines do not routinely recommend dual antiplatelet therapy for vertebral artery dissection:

• The standard recommendation is for either aspirin or clopidogrel as monotherapy 1
• Dual antiplatelet therapy (aspirin + clopidogrel) increases hemorrhage risk and is not routinely recommended for standard ischemic stroke prevention 1
• The exception would be if the dissection is being treated similarly to acute ischemic stroke protocols in the first 21-90 days, though this is not specifically addressed in dissection guidelines 1

Clinical Decision Algorithm

When choosing between antiplatelet vs anticoagulation therapy:

1. Check for contraindications to anticoagulation:

   • Subarachnoid hemorrhage from intracranial extension of dissection (absolute contraindication to anticoagulation) 1
   • Risk of hemorrhagic transformation (though this risk is low at <5% with heparin) 1

2. If no contraindications exist, either approach is acceptable based on CADISS trial results 1, 2

3. Practical considerations favoring antiplatelet therapy:

   • Simpler administration and monitoring 1
   • No INR monitoring required 1
   • Lower bleeding risk profile 1
   • Equivalent efficacy to anticoagulation 1, 3

4. Duration: 3-6 months of antithrombotic therapy 1, 4

The Natural History Supports Conservative Medical Management

Understanding the benign natural history helps explain why aggressive intervention isn't needed:

• Recurrent stroke risk is remarkably low: 1-4% over 2-5 years 1
• Anatomic healing with recanalization occurs in 72-100% of patients 1
• Dissections that don't fully heal are not associated with increased recurrent stroke risk 1
• The greatest stroke risk is in the first few days after initial vascular injury 1

Critical Pitfalls to Avoid

Don't Rush to Endovascular Intervention

• Endovascular therapy (stenting) should be reserved only for patients with persistent or recurrent symptoms despite antithrombotic therapy 1
• It is not indicated as initial treatment given the low recurrence rates with medical therapy alone 1

Don't Use Anticoagulation if Intracranial Extension Exists

• Anticoagulation may adversely affect outcomes if subarachnoid hemorrhage occurs from intracranial extension 1, 4
• Intracranial vertebral dissections carry higher rupture risk 1

Don't Forget Comprehensive Vascular Risk Factor Management

Beyond antithrombotic therapy, patients require:

• High-intensity statin therapy to reduce LDL below 70 mg/dL (Class I recommendation) 4
• Blood pressure control with target systolic <140 mmHg 4, 5
• Smoking cessation 4
• These interventions address the systemic atherosclerotic risk that often coexists 4

Why the Prognosis is Usually Favorable

With appropriate antithrombotic treatment:

• The prognosis is typically excellent 1, 4
• Good functional outcome (modified Rankin Score ≤2) occurs in approximately 75% of patients 6
• The actual stroke recurrence rate in randomized trials is much lower than feared from older observational data 3