What is the latest approach in imaging for a suspected stroke patient?

Latest Approach in Imaging for Suspected Stroke Patients

All patients with suspected acute stroke should undergo immediate non-contrast CT (NCCT) of the head as the first-line imaging modality to differentiate hemorrhagic from ischemic stroke, with imaging completed and interpreted within 45 minutes of emergency department arrival. 1

Initial Imaging Strategy

The primary goal is rapid exclusion of hemorrhage and assessment for early ischemic changes to determine treatment eligibility. 1

For IV Thrombolysis Candidates (0-4.5 hour window):

• Perform NCCT immediately without waiting for additional imaging to assess eligibility for IV tPA 1
• NCCT must exclude intracranial hemorrhage and assess for early ischemic changes (hypodensity, loss of gray-white differentiation, sulcal effacement) 1
• Initiate IV tPA based on NCCT alone—do not delay treatment waiting for vascular imaging 1
• Frank hypodensity involving >1/3 of middle cerebral artery territory is a relative contraindication due to hemorrhagic transformation risk 2

For Endovascular Therapy Candidates (0-6 hour window):

Immediately follow NCCT with CT angiography (CTA) from aortic arch to vertex to identify large vessel occlusions amenable to mechanical thrombectomy. 1 This combined protocol should not delay IV tPA administration if the patient is eligible. 1

Three acceptable imaging pathways exist for endovascular consideration: 1

• NCCT followed immediately by digital subtraction angiography
• NCCT plus CTA with or without CT perfusion
• MRI plus MR angiography with or without perfusion imaging

Use a validated triage tool such as ASPECTS to rapidly identify EVT candidates who may require transfer to comprehensive stroke centers. 1

Advanced Imaging Considerations

CT Perfusion (CTP):

• May be considered for patient selection but must not substantially delay treatment decisions 1
• Most valuable for late-window patients (>6 hours) or unknown onset to identify salvageable tissue 1, 2
• Has technical failure rates up to 30% and lacks standardized quantification across vendors 1
• Not necessary for clinical decision-making within the 6-hour window when NCCT and CTA are adequate 1

Multiphase CTA:

• Provides information about collateral circulation status and procedural planning 1
• Offers valuable data on extracranial vessel tortuosity for intervention planning 1

MRI as Alternative Initial Imaging

While MRI with diffusion-weighted imaging (DWI) is superior to CT for detecting acute ischemia (sensitivity 83% vs 26% for any acute stroke), 3, 4 CT remains the preferred initial modality in most centers due to: 1

• Faster acquisition time (critical for treatment window)
• 24/7 availability in most emergency departments
• No contraindications (pacemakers, metallic implants)
• Less susceptibility to patient motion
• Easier interpretation for providers with limited expertise

MRI can be used as the primary imaging modality if immediately available and does not delay treatment, particularly in centers with streamlined protocols achieving 10-minute acquisition times. 2, 3

Hemorrhagic Stroke Imaging

If NCCT demonstrates intraparenchymal hemorrhage (15% of all strokes): 1

• Perform CTA of intracranial arteries acutely to evaluate for underlying vascular malformation or aneurysm 1
• Consider MRI with contrast in subacute phase (once hematoma resorbs) to assess for underlying neoplastic or vascular mass, microhemorrhages suggesting amyloid angiopathy, or other etiologies 1

Critical Pitfalls to Avoid

The most critical error is delaying IV tPA while waiting for advanced imaging—if the patient presents within 4.5 hours with no contraindications on NCCT, initiate thrombolysis immediately. 2 Additional vascular imaging can be obtained concurrently or immediately after tPA bolus. 1

Do not use CTP as a reason to exclude patients from treatment based on apparent large core volumes, as the core-penumbra concept has been challenged and some "core" regions may have selective neuronal loss rather than pan-necrosis. 1

Avoid performing contrast-enhanced CT or MRI as initial imaging—it provides no additional benefit for acute stroke diagnosis and delays treatment. 2

Optimal Practical Protocol

The most efficient approach combines NCCT followed immediately by multiphase CTA 1:

1. NCCT to exclude hemorrhage and estimate ischemic core using ASPECTS
2. Multiphase CTA to detect/localize occlusion, estimate collaterals, and enable procedural planning
3. This protocol is fast, available 24/7, inexpensive, robust against patient motion, and easy to interpret 1

This streamlined approach provides all necessary information for both IV thrombolysis and endovascular therapy decisions without treatment delays. 1