How to investigate for vertebral artery dissection?

Investigation of Vertebral Artery Dissection

CT angiography (CTA) of the head and neck with IV contrast is the preferred initial diagnostic modality for investigating vertebral artery dissection due to its highest reported sensitivity (100%) compared to MRA (77%) and Doppler ultrasound (71%). 1, 2

Diagnostic Imaging Options

First-Line Imaging

• CT Angiography (CTA) of Head and Neck with IV Contrast
  • Highest sensitivity (100%) for vertebral artery dissection compared to other modalities 1
  • Allows evaluation of course and luminal caliber of arteries 1
  • Can detect luminal filling defects including dissection flaps, thrombus, and vascular webs 1
  • Should include the entire vertebral artery from origin at aortic arch to basilar artery 1

Alternative Imaging Options

• MR Angiography (MRA) of Head and Neck

  • Sensitivity of approximately 77% compared to conventional angiography 1, 2
  • MRA of the neck is best performed with contrast for better evaluation of vessels with increased spatial resolution 1
  • Addition of nonluminal vessel wall imaging sequences may improve detection of nonstenotic arterial dissection 1
  • Contrast-enhanced MRA has shown sensitivity, specificity, and accuracy as high as 97%, 98%, and 93% respectively for vertebral artery origin stenosis 1

• Doppler Ultrasonography

  • Lowest sensitivity (71%) among the three main imaging modalities 1, 2
  • May identify dissection flap and differential flow in true and false lumens 1
  • Limited utility for dissections beginning above the angle of the mandible 1
  • More operator-dependent than CTA or MRA 2

Advanced/Specialized Imaging

• Catheter-based Digital Subtraction Angiography
  • Traditional gold standard but now largely supplanted by CTA and MRA 1
  • May be necessary in select cases to delineate collateral filling via circle of Willis 1
  • Reserved for cases where non-invasive imaging is inconclusive or when endovascular intervention is being considered 1, 3

Common Imaging Findings in Vertebral Artery Dissection

• Vertebral artery stenosis (51% of cases) 2
• String and pearls appearance (48% of cases) 2
• Arterial dilation (37% of cases) 2
• Arterial occlusion (36% of cases) 2
• Pseudoaneurysm, double lumen, and intimal flap (22% each) 2

Clinical Pearls and Pitfalls

• No single radiographic sign is present in the majority of vertebral artery dissection patients, making diagnosis challenging 2
• Because symptomatic dissection may involve any portion of the vertebral artery, imaging should include the entire vessel from origin to basilar artery 1
• Maintain high index of suspicion in younger patients with posterior circulation stroke symptoms, as vertebral artery dissection accounts for 10-15% of ischemic strokes in patients under 45 years 1, 3
• Nonspecific radiographic signs predominate, requiring careful interpretation by experienced radiologists 2, 4
• Initial negative imaging does not exclude dissection; follow-up imaging may be necessary if clinical suspicion remains high 5

Diagnostic Algorithm

1. Begin with CTA head and neck with IV contrast as first-line imaging due to highest sensitivity 1, 2
2. If CTA is contraindicated or unavailable, proceed with contrast-enhanced MRA of head and neck 1
3. If both CTA and MRA are unavailable, Doppler ultrasonography may be used with awareness of its limitations 1, 2
4. Consider catheter-based angiography only if non-invasive imaging is inconclusive or intervention is planned 1
5. Include vessel wall imaging sequences when using MRI/MRA to improve detection of non-stenotic dissections 1