What is the role of CT angiogram of the neck in diagnosing and managing suspected stroke?

CT Angiography of the Neck in Suspected Stroke

CTA of the neck is a rapid, highly sensitive imaging modality that should be performed in the acute stroke setting to evaluate extracranial vasculature for carotid stenosis, dissection, and other steno-occlusive diseases that guide treatment decisions and surgical planning for endovascular therapy. 1

Role in Acute Stroke Evaluation

Primary Indications

• CTA neck is the most rapid means of assessing extracranial vasculature in acute stroke and can be rapidly acquired together with CTA head to elucidate stroke etiology and facilitate endovascular surgical planning for large vessel occlusion (LVO). 1

• The degree of vascular tortuosity identified on CTA neck directly correlates with time from groin puncture to recanalization and must be factored into decision-making regarding indications and surgical approach, including choice of radial artery or direct carotid puncture access. 1

• CTA neck combined with CTA head provides comprehensive assessment of potential extracranial sources of thromboembolism in acute stroke evaluation. 2

Timing Recommendations

• The American Heart Association guidelines recommend noninvasive imaging of cervical carotid arteries within 48 hours of onset for patients with TIA or minor stroke who are candidates for carotid endarterectomy (CEA) or stenting. 1

• For patients with minor stroke who are CEA/stenting candidates, imaging should occur within 24 hours of hospitalization or 48 hours of symptom onset due to the high early risk of recurrent stroke in patients with symptomatic carotid stenosis. 1

Clinical Scenarios Where CTA Neck is Essential

Acute Ischemic Stroke

• CTA neck is useful for endovascular surgical planning in patients with LVO by identifying vessel tortuosity, stenosis, and anatomic variants that affect procedural approach. 1

• In late-presenting strokes, CTA neck rapidly evaluates for carotid stenosis and other cervical steno-occlusive disease, though the urgency of diagnosis is less well-defined compared to hyperacute presentations. 1

TIA and Minor Stroke

• CTA neck is a rapid means of evaluating extracranial vasculature and is useful in initial workup and triage of carotid territory TIA. 1, 3

• CTA has sensitivity and specificity approaching 98% for suspected cervical vascular dissection or injury. 2

Cryptogenic Stroke

• In cryptogenic stroke, CTA neck may diagnose unsuspected carotid webs or features of unstable plaque that would otherwise be missed. 1

Diagnostic Performance

Accuracy for Carotid Stenosis

• CTA demonstrates 100% sensitivity and high negative predictive value (100%) for detecting ≥70% internal carotid artery stenosis when compared to digital subtraction angiography. 4

• CTA provides twice the spatial resolution of MRA, approaching that of conventional angiography with modern multidetector scanners. 5

Detection of Vascular Pathology

• CTA allows detection of vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap in suspected cervical artery dissection. 2

• CTA has sensitivity 90-100% and specificity 98.6-100% for penetrating neck trauma evaluation. 2

Important Limitations and Pitfalls

Technical Limitations

• Heavy calcifications or calcified plaque on both sides of the lumen can lead to overestimation of stenosis, particularly in the setting of dense carotid calcification. 1, 2, 5

• CTA typically overestimates stenosis compared to carotid Doppler ultrasound, especially with bilateral disease or severe calcification. 1

• Streak artifact from metallic foreign bodies may limit evaluation in trauma patients. 2

Clinical Considerations

• Iodinated contrast requirement may be contraindicated in patients with severe renal impairment or contrast allergy, in which case MRA neck becomes the alternative. 2

• Radiation exposure is a consideration, especially for young patients or those requiring repeated imaging. 2

Alternative Imaging When CTA is Contraindicated

• MRA of the neck is an acceptable alternative if contraindications to CTA exist (renal impairment, contrast allergy), though it tends to overestimate the degree of carotid stenosis without contrast administration and is limited by respiratory motion artifacts in evaluating vertebral origin disease. 1, 5

• In the absence of bilateral disease, carotid Doppler ultrasound is more accurate than CTA in evaluating the degree of carotid stenosis. 1

Practical Implementation

Protocol Optimization

• A "one-stop-shop" protocol combining brain CTP and head-and-neck CTA can reduce imaging time by 43% and contrast dose by 40% without affecting image quality, using 256-detector CT systems. 6

• The examination should include both head and neck CTA when evaluating acute stroke to provide comprehensive vascular assessment from aortic arch to circle of Willis. 1

Integration with Stroke Workflow

• CTA neck should be performed immediately following noncontrast CT head in the acute stroke protocol to minimize time to treatment decision. 1

• The vascular information from CTA neck directly influences decisions regarding antiplatelet therapy, anticoagulation, and need for urgent revascularization procedures. 1