In a young patient with acute stroke symptoms and a normal non‑contrast CT brain, why is a computed tomography angiography (CTA) of the brain and neck indicated, and which vascular anomalies might be responsible?

Why CTA Brain and Neck is Essential in Young Stroke Patients

In young stroke patients with normal non-contrast CT, CTA of the brain and neck is critical to identify large vessel occlusions requiring endovascular therapy and to detect specific vascular anomalies that are common stroke etiologies in this age group—particularly arterial dissection, which accounts for approximately 15% of young strokes 1, 2.

Primary Indications for CTA in Young Stroke

Detection of Large Vessel Occlusion

CTA rapidly identifies intracranial vessel occlusions with 92-100% sensitivity and 82-100% specificity 1. This is crucial because:

• The majority of large strokes result from large vessel occlusion
• Early identification determines eligibility for mechanical thrombectomy
• CTA provides this information without delaying treatment (no significant difference in door-to-needle times compared to non-contrast CT alone) 3

Identification of Age-Specific Stroke Etiologies

In young adults (18-50 years), the diagnostic yield reveals distinct patterns:

Cervical arterial dissection is the most common vascular abnormality identified:

• Found in 14.7% of young stroke patients on ipsilateral CTA 2
• Significantly more common than contralateral dissections (2.9%, p=0.001) 2
• Often occurs in the absence of traditional atherosclerotic risk factors

Other critical findings include:

• Carotid webs: 2.2% of cases, exclusively ipsilateral to infarct 2
• Atherosclerotic stenosis: Mean ipsilateral stenosis of 14.1% vs 6.5% contralateral (p=0.006), with 17.9% showing ≥50% stenosis 2, 4
• Vulnerable plaque: Present in 42.9% of young stroke patients 4
• Intracranial vascular malformations: Including arteriovenous malformations and aneurysms (sensitivity >90% for detection) 5

When Non-Contrast CT is Normal: What CTA Reveals

A normal non-contrast CT does not exclude:

1. Acute large vessel occlusion - May not show parenchymal changes in hyperacute phase (<3 hours)
2. Small cortical or posterior fossa infarcts - Below CT resolution
3. Underlying vascular pathology causing the stroke:
   • Arterial dissection (no hemorrhage visible on plain CT)
   • High-grade stenosis without completed infarction
   • Intracranial atherosclerosis
   • Moyamoya syndrome
   • Reversible cerebral vasoconstriction syndrome

Clinical Algorithm for CTA Utilization

Perform CTA brain and neck emergently when:

• Age <50 years with stroke symptoms
• Non-contrast CT shows no hemorrhage
• Patient is within potential treatment window for thrombectomy (up to 24 hours in selected cases)
• Need to determine stroke mechanism for secondary prevention

The combined head and neck CTA protocol is superior to head alone because:

• Cervical dissection extends from neck vessels into intracranial circulation
• Carotid webs occur at the carotid bulb (cervical location)
• Atherosclerotic disease often involves both cervical and intracranial segments
• Treatment planning for endovascular intervention requires visualization of access route 5

Safety Considerations

Renal safety is not a barrier to emergent CTA:

• No significant difference in acute kidney injury rates between CTA and non-contrast CT groups (5 vs 7 cases, p=0.422) 3
• No significant change in serum creatinine at 24-48 hours (ΔCr: -0.07 CTA vs -0.11 non-contrast, p=0.489) 3
• Do not delay CTA for laboratory confirmation of renal function in the acute stroke setting 3

Common Pitfalls to Avoid

1. Assuming normal non-contrast CT excludes treatable pathology - CTA identifies actionable findings in 35% of cases (high-grade stenoses/occlusions) plus 10.2% vascular anomalies 3

2. Ordering head CTA without neck imaging - This misses cervical dissections and carotid webs, the most common young stroke etiologies 2

3. Delaying CTA for renal function testing - This is unnecessary and delays critical treatment decisions 3

4. Relying on clinical examination alone - Vascular imaging is essential to establish stroke mechanism and prevent recurrence 1

The number needed to scan is only 14 to find a vascular abnormality, making CTA highly efficient in the young stroke population where therapeutic consequences are significant 6.