Best Imaging for Vertebral Artery Occlusion
CT angiography (CTA) of the head and neck with IV contrast is the preferred initial imaging modality for vertebral artery occlusion, offering 100% sensitivity and the fastest time to diagnosis in the acute setting. 1, 2
Primary Imaging Recommendation
CTA head and neck with IV contrast should be performed immediately as the first-line diagnostic study. 3, 1, 4, 2 This modality provides:
- 100% sensitivity for vertebral artery occlusion compared to 77% for MRA and 71% for Doppler ultrasound 1, 2
- Rapid acquisition time critical for time-dependent treatment decisions 3
- Comprehensive visualization from aortic arch origin through the basilar artery in a single acquisition 3, 1, 2
- Direct visualization of the occlusion site, dissection flap, luminal filling defects, and vessel caliber 1, 4, 2
- Concurrent evaluation of both extra- and intracranial vasculature 3
The imaging protocol must include coverage from the aortic arch to the circle of Willis, as symptomatic vertebral artery pathology can occur at any level. 1, 4, 2
Alternative Imaging When CTA is Contraindicated
MRA of the head and neck should be used when iodinated contrast is contraindicated (renal insufficiency or contrast allergy). 3, 2
- Time-of-flight (TOF) MRA can be performed without contrast 3
- Sensitivity is 77% compared to conventional angiography 1, 2
- Contrast-enhanced MRA provides better spatial resolution and vessel evaluation 2
- MRA with vessel wall imaging sequences adds diagnostic capability for dissection characterization 4
However, MRA may delay endovascular therapy in acute large vessel occlusion, which represents a critical harm given the time-dependent nature of stroke treatment. 3
Role of Catheter Angiography
Digital subtraction angiography (DSA) should be reserved for specific situations: 1, 4, 2
- When CTA and MRA are inconclusive 3, 1
- When endovascular intervention is being considered 3, 1, 2
- To evaluate collateral circulation via the circle of Willis 2
- For dynamic assessment of rotational vertebral artery occlusion with head turning 5, 6, 7
DSA offers the highest spatial and temporal resolution but is invasive and no longer first-line given the comparable accuracy of modern multidetector CTA. 3
Complementary Non-Contrast CT
Non-contrast CT head should be obtained concurrently to: 3, 4
- Exclude hemorrhagic stroke, which fundamentally changes management 3
- Assess for mass effect in the posterior fossa 4
- Evaluate extent of early ischemic changes 3
The radiation dose of combined non-contrast CT plus CTA is approximately 8.5 mSv, which is acceptable given the diagnostic necessity. 3
Doppler Ultrasound Limitations
Doppler ultrasonography has limited utility as a primary diagnostic modality: 2
- Sensitivity of only 71% for vertebral artery dissection 2
- Cannot visualize dissections above the angle of the mandible 2
- More operator-dependent than CTA or MRA 2
- Does not provide information necessary to determine eligibility for endovascular therapy 3
Critical Clinical Pitfalls
Maintain high suspicion for vertebral artery occlusion in patients under 45 years with posterior circulation symptoms, as dissection accounts for 10-15% of strokes in this age group. 1, 4, 2
Dynamic angiography with head rotation is essential when rotational vertebral artery occlusion is suspected, as static imaging may miss the true level of obstruction. 5, 6, 7 Standard CTA performed in neutral head position may not demonstrate compression that occurs only with rotation. 7
The entire vertebral artery course must be imaged, as misdiagnosis of the occlusion level or missing a second occlusive site can lead to inappropriate treatment. 1, 2, 7
Time-Critical Considerations
In acute stroke due to large vessel occlusion, imaging protocols must be streamlined to avoid treatment delays that directly worsen outcomes. 3 The rapidity of CTA acquisition (typically <5 minutes) makes it strongly preferable to MRI in the hyperacute setting, where every minute of delay increases morbidity and mortality. 3