Why do we order a CT (Computed Tomography) Angio (Angiography) head and neck in patients presenting with stroke-like symptoms?

CT Angiography of Head and Neck in Stroke-Like Symptoms

CT Angiography (CTA) of the head and neck is ordered in patients with stroke-like symptoms to rapidly identify large vessel occlusions, evaluate the etiology of stroke, and guide appropriate treatment decisions including eligibility for endovascular therapy. 1

Primary Purposes of CTA Head and Neck

1. Identification of Large Vessel Occlusions (LVOs)

   • CTA has high sensitivity and specificity for detecting intracranial LVOs 1
   • Rapid identification is critical as LVO strokes are medical emergencies requiring immediate intervention
   • Guides eligibility for endovascular thrombectomy, especially within the critical time windows

2. Evaluation of Vascular Anatomy

   • Assesses both intracranial and extracranial vasculature in a single examination
   • Identifies stenosis, occlusion, dissection, or other vascular abnormalities 1
   • Evaluates collateral circulation, which correlates with outcomes after thrombolytic therapy 2

3. Treatment Planning

   • Informs eligibility for specific interventions:
     • Endovascular thrombectomy for LVOs
     • Carotid endarterectomy or stenting for significant carotid stenosis
   • Helps determine surgical approach based on vascular tortuosity 1

Imaging Protocol in Acute Stroke

The American College of Radiology recommends the following sequence 1:

1. Non-contrast CT head - First to:

   • Exclude hemorrhage (absolute contraindication to thrombolytics)
   • Assess for early ischemic changes
   • Evaluate ASPECTS score to determine extent of completed infarct

2. CTA head and neck - Immediately following non-contrast CT:

   • Rapidly acquired in the same session without moving the patient
   • Provides comprehensive vascular assessment in minutes

Timing Considerations

• 0-4.5 hour window: CTA helps determine eligibility for IV thrombolysis and endovascular therapy
• 6-24 hour extended window: CTA combined with CT perfusion helps identify patients who may benefit from late endovascular therapy 1
• TIA or minor stroke: Current AHA guidelines recommend vascular imaging within 24 hours of hospitalization or 48 hours of symptom onset 1

Advantages of CTA Over Other Modalities

• Speed: Faster acquisition than MRA, critical in time-sensitive stroke care 1
• Availability: More widely available in emergency settings
• Sensitivity: High sensitivity (100%) and negative predictive value for carotid stenosis 3
• Compatibility: No contraindications related to implanted devices (unlike MRI)

Common Pitfalls and Limitations

• Contrast-related issues:

  • Potential for contrast-induced nephropathy in patients with renal impairment
  • Allergic reactions to iodinated contrast

• Technical limitations:

  • Heavy calcifications can lead to overestimation of carotid stenosis 1
  • Motion artifacts can degrade image quality

Special Considerations

• In patients with renal impairment or contrast allergy, MRA without contrast may be an alternative 1
• For patients with suspected LVO but contraindications to CTA, proceeding directly to cerebral angiography after non-contrast CT may be considered in select cases 1

CTA head and neck has become an essential component of acute stroke imaging protocols, providing critical information that directly impacts treatment decisions and patient outcomes. Its rapid acquisition and high diagnostic accuracy make it invaluable in the time-sensitive management of stroke.