Do you perform a CT (Computed Tomography) scan in a wake-up stroke?

CT Imaging for Wake-Up Stroke

Yes, all patients with wake-up stroke should undergo immediate non-contrast CT imaging as the initial diagnostic test, followed by CT angiography to guide treatment decisions. 1

Initial Imaging Protocol for Wake-Up Stroke

Primary Imaging (Required)

1. Non-contrast CT (NCCT) - Must be performed immediately to:

   • Rule out hemorrhage
   • Evaluate for early ischemic changes
   • Assess ASPECTS score (Alberta Stroke Program Early CT Score)
   • Guide eligibility for thrombolysis and endovascular therapy 1

2. CT Angiography (CTA) - Should be performed immediately after NCCT:

   • Identifies large vessel occlusions
   • Evaluates from arch-to-vertex including extra- and intra-cranial circulation
   • Essential for determining eligibility for endovascular thrombectomy 1

Advanced Imaging (Recommended for Wake-Up Strokes)

1. CT Perfusion (CTP) or multiphase/dynamic CTA:
   • Particularly valuable in wake-up strokes to assess salvageable brain tissue
   • Helps identify patients who may benefit from treatment despite unknown onset time
   • Should not substantially delay treatment decisions 1

Rationale for Imaging in Wake-Up Stroke

Wake-up strokes represent approximately 25% of all ischemic strokes 2. Since the exact time of symptom onset is unknown, imaging becomes critical for treatment decisions. Evidence suggests that many wake-up strokes occur close to awakening, meaning patients may still be within treatment windows when they present 3.

The considerable prevalence of CT perfusion mismatch and intracranial artery occlusions in wake-up stroke patients suggests that arterial and perfusion imaging is particularly important in this population 2. Studies have shown that clinical and imaging characteristics of wake-up stroke patients are often similar to those with known onset times who are eligible for treatment 4.

Treatment Considerations Based on Imaging

• For thrombolysis candidates: NCCT is essential to exclude hemorrhage and evaluate early ischemic changes 1, 5
• For endovascular therapy candidates: Both NCCT and CTA are required to identify large vessel occlusions 1
• For patients >6 hours from last known well: Advanced imaging with CTP is recommended to identify salvageable tissue 1

Important Considerations

• The ASPECTS score from NCCT is a validated tool to rapidly identify patients who may be eligible for treatment 1
• Studies show that 85.2% of wake-up stroke patients have favorable NCCT ASPECTS >7, and 75% have both favorable ASPECTS and good collateral filling 4
• Observational studies suggest that thrombolysis can be safely administered to wake-up stroke patients with normal non-contrast brain CTs 6

Pitfalls to Avoid

1. Delaying treatment: Imaging should be performed rapidly and should not substantially delay treatment decisions 1, 5
2. Overreliance on time windows: For wake-up strokes, tissue status on imaging may be more important than time since last known well 3
3. Missing posterior circulation strokes: NCCT has limited sensitivity for detecting small acute infarcts or those in the posterior fossa 1, 5
4. Ignoring early ischemic signs: Subtle signs like hyperdense middle cerebral artery sign, loss of gray-white differentiation, and sulcal effacement are important to identify 1, 5

By following this imaging protocol, clinicians can make informed decisions about treatment options for wake-up stroke patients, potentially expanding treatment opportunities for this substantial group of stroke patients.