What is the next step if beading is seen on Computed Tomography Angiography (CTA) of the head and neck?

Beading on CTA Head/Neck: Next Imaging Step

When beading is identified on CTA of the head and neck, the next step is catheter cerebral angiography (digital subtraction angiography), which is the gold standard for definitive diagnosis and characterization of vasculitis and other arteriopathies causing this appearance. 1

Understanding the Clinical Context

Beading on CTA—characterized by alternating areas of arterial narrowing and dilatation—is a classic finding suggestive of:

• Central nervous system (CNS) vasculitis (primary angiitis or secondary to systemic disease) 1
• Fibromuscular dysplasia 2
• Arterial dissection (though typically presents with other features) 1
• Reversible cerebral vasoconstriction syndrome 1

Why Catheter Angiography is Essential

Catheter angiography (arteriography cervicocerebral) receives the highest appropriateness rating (9/9 - "usually appropriate") for evaluation of suspected CNS vasculitis and vascular malformations. 1

Key advantages include:

• Superior spatial and temporal resolution compared to CTA or MRA, allowing detection of subtle vessel irregularities that may be missed on noninvasive imaging 2
• Dynamic flow assessment that provides true anatomical depiction rather than just a flow map 2
• Ability to detect small vessel involvement that falls below the resolution threshold of CTA/MRA 1
• Definitive characterization of vessel wall abnormalities, stenosis severity, and collateral circulation 1, 2

Complementary MRI/MRA Considerations

While proceeding to catheter angiography, MRI head without and with IV contrast (rated 8/9) plus MRA head without and with IV contrast (rated 8/9) should be strongly considered as complementary studies if not already performed: 1

• MRI with contrast is superior for detecting parenchymal complications including infarcts, hemorrhage, and inflammatory changes in vessel walls 1
• Vessel wall imaging sequences (fat-suppressed T1-weighted) can directly visualize mural hematoma in dissection with sensitivity and specificity superior to CT 1
• MRA can be useful for problem-solving after initial CTA, though it has lower sensitivity (77%) compared to CTA (100%) for dissection 1

Clinical Algorithm

1. Immediate assessment: Evaluate for acute stroke symptoms requiring emergent intervention 1

2. Proceed to catheter angiography for definitive diagnosis when beading is seen on CTA 1, 2

3. Obtain MRI/MRA (if not contraindicated) to assess parenchymal injury and provide complementary vascular information 1

4. Consider clinical context:

   • Recent trauma → dissection more likely 1, 3
   • Headache with neurologic symptoms → vasculitis or reversible vasoconstriction 1
   • Young patient → fibromuscular dysplasia or moyamoya 1

Critical Pitfalls to Avoid

• Do not rely solely on CTA or MRA for definitive diagnosis of vasculitis, as these modalities can miss small vessel disease and provide false negatives 1, 2
• Do not delay catheter angiography in stable patients when beading is identified, as this is the only technique that adequately defines the vascular pathology 1, 2
• Remember that MRA shows flow maps, not true anatomy—slow flow can cause signal loss and lead to false positive interpretations 2
• Beware that noninvasive imaging may underestimate the extent of vascular involvement, particularly in small vessel vasculitis 1