Should a CT (Computed Tomography) scan with or without contrast be used for Transient Ischemic Attack (TIA) assessment?

CT With or Without Contrast for TIA Assessment

For initial TIA evaluation, use noncontrast CT head without IV contrast to exclude hemorrhage and stroke mimics, followed immediately by CTA head and neck with IV contrast to evaluate for treatable vascular lesions. 1

Initial Imaging: Noncontrast CT Head is Essential

Noncontrast CT head without IV contrast is the mandatory first imaging study in all TIA patients. 1, 2, 3 This serves several critical functions:

• Excludes intracranial hemorrhage, which is an absolute contraindication to thrombolytics, anticoagulants, and antiplatelet agents used to prevent recurrent stroke 1, 3
• Identifies stroke mimics including intracranial masses, infections, and other alternative etiologies that can present with TIA-like symptoms 1
• Detects early ischemic changes that correlate with subsequent stroke risk, regardless of chronicity 1

CT Head With IV Contrast Alone Has No Role

The American College of Radiology explicitly states there is no relevant literature supporting the use of CT head with IV contrast in TIA evaluation. 1, 3 Contrast administration may actually obscure early complications such as hemorrhage, making it counterproductive. 3

When to Add CTA (With Contrast)

After excluding hemorrhage on noncontrast CT, immediately proceed to CTA head and neck with IV contrast for vascular evaluation. 1, 2

CTA Head With IV Contrast:

• Rapidly evaluates intracranial vasculature for atherosclerosis and steno-occlusive disease that may guide treatment decisions 1
• Useful in secondary workup and triage of TIA patients 1

CTA Neck With IV Contrast:

• Essential for carotid territory TIAs to evaluate extracranial vasculature 1
• American Heart Association guidelines recommend noninvasive carotid imaging within 48 hours for patients who are candidates for carotid endarterectomy or stenting 1, 2
• The 90-day risk of ipsilateral stroke in symptomatic carotid disease is 20.1%, making rapid vascular imaging critical 1, 2

Common pitfall: Heavy calcifications can lead to overestimation of stenosis severity on CTA. 1

Alternative Vascular Imaging in Special Circumstances

For patients with renal impairment, contrast allergy, or repeat presentations, use MRA head and neck without IV contrast instead of CTA. 1, 4

• Time-of-flight (TOF) MRA is sufficiently sensitive to screen for culprit intracranial and extracranial lesions 1, 4
• Important caveat: Noncontrast MRA tends to overestimate stenosis severity, particularly in high-grade stenosis 1, 4
• Ultrasound duplex carotid Doppler is another noninvasive alternative for extracranial vascular evaluation 1, 4

CT Perfusion Has Limited Role

CT perfusion with IV contrast is not typically used for initial TIA assessment. 1 While it can identify perfusion abnormalities in up to one-third of TIA cases, selection of patients for revascularization based on hemodynamic compromise does not improve outcomes. 1

Critical Timing Considerations

Imaging must be performed urgently to prevent recurrent stroke:

• Stroke risk after TIA is 8.8% at 7 days and 11.6% at 90 days 1, 2
• Patients should have access to imaging within 12 hours of presentation 2
• Carotid imaging should be completed within 48 hours for surgical candidates 1, 2

Delaying imaging beyond 48 hours significantly increases recurrent stroke risk. 2

Practical Algorithm

1. Start with noncontrast CT head in all suspected TIA patients to exclude hemorrhage and mimics 1, 2, 3
2. If hemorrhage is excluded, immediately add CTA head and neck to evaluate for treatable vascular lesions 1, 2
3. For patients with renal impairment (eGFR <30) or contrast allergy, substitute MRA without contrast or ultrasound duplex 1, 4
4. Complete vascular imaging within 48 hours for all carotid territory TIA patients 1, 2