What is the recommended initial imaging and laboratory evaluation approach to diagnose hemorrhagic vs embolic stroke?

Clinical Diagnosis of Hemorrhagic vs Embolic Stroke

Non-contrast CT scan of the brain is the initial imaging modality of choice to distinguish between hemorrhagic and ischemic stroke, followed by vascular imaging with CT angiography from aortic arch to vertex. 1

Initial Imaging Approach

Primary Imaging

1. Non-contrast CT brain - Must be performed immediately for all suspected stroke patients 1

   • Gold standard for detecting acute hemorrhage 1
   • Should be completed within 25 minutes of arrival 1
   • Identifies hemorrhagic stroke with high sensitivity
   • Rules out hemorrhage before thrombolytic therapy consideration

2. CT Angiography (CTA) - Should be performed immediately after non-contrast CT 1

   • Include extracranial and intracranial arteries ("aortic arch-to-vertex") 1
   • Identifies large vessel occlusions
   • Helps determine eligibility for endovascular therapy
   • Can identify contrast extravasation within hematoma, suggesting risk of hematoma expansion 1

Alternative or Supplementary Imaging

• MRI with diffusion-weighted imaging (DWI) and gradient echo (GRE) or T2* sequences
  • As sensitive as CT for detecting acute hemorrhage 1
  • More sensitive for identifying prior hemorrhage 1
  • Better for posterior circulation strokes and small infarcts
  • May be necessary for wake-up strokes or anterior circulation strokes with large infarcts 1

Laboratory Evaluation

The following laboratory tests should be performed as part of the initial evaluation 1:

1. Complete blood count - Evaluates for thrombocytopenia or polycythemia
2. Coagulation studies - INR, aPTT to identify coagulopathies
3. Electrolytes - Identifies metabolic abnormalities
4. Blood glucose - Rules out hypoglycemia mimicking stroke
5. Renal function - Creatinine, eGFR (especially if contrast agents will be used)
6. Electrocardiogram (ECG) - Identifies cardiac arrhythmias or evidence of structural heart disease

Distinguishing Features on Imaging

Hemorrhagic Stroke Features

• Hyperdense area on non-contrast CT representing acute blood 1
• Well-defined borders initially
• May have surrounding edema
• Location can provide clues (basal ganglia, thalamus, cerebellum, and lobar regions are common)
• Mass effect may be present
• On MRI: hyperintense on T1-weighted images (subacute phase) and hypointense on T2* sequences

Ischemic/Embolic Stroke Features

• Early signs on CT may be subtle:
  • Loss of gray-white matter differentiation
  • Hyperdense vessel sign (indicating thrombus in artery)
  • Insular ribbon sign
  • Obscuration of lentiform nucleus
• On MRI: hyperintense on DWI with corresponding hypointensity on apparent diffusion coefficient (ADC) maps
• Vascular imaging may show arterial occlusion or stenosis

Pitfalls and Caveats

1. Timing matters: CT may not show ischemic changes in the first few hours after symptom onset

   • 28-38% of patients with ICH imaged within 3 hours show hematoma expansion on follow-up CT 1

2. Hemorrhagic transformation of ischemic stroke:

   • Can be confused with primary hemorrhagic stroke
   • More common in embolic strokes (22%) than thrombotic strokes (10%) 2
   • Often occurs between 12-48 hours after stroke onset 3
   • Associated with large infarcts (82% of cases) 3

3. Secondary causes of hemorrhage:

   • Unusual hematoma shape, presence of subarachnoid hemorrhage, or edema out of proportion to timing should raise suspicion 1
   • Consider arteriovenous malformations, tumors, cerebral vein thrombosis

4. Stroke mimics:

   • Approximately 20-30% of cases initially labeled as stroke or TIA are actually mimics 1
   • Close working relationship between emergency department staff and stroke specialists is essential

Algorithm for Diagnosis

1. Immediate non-contrast CT brain on arrival

2. If hemorrhage present → Manage as hemorrhagic stroke

   • Consider CTA to evaluate for underlying vascular abnormalities
   • Consider MRI/MRV if cerebral venous thrombosis is suspected

3. If no hemorrhage → Proceed with CTA from aortic arch to vertex

   • If large vessel occlusion identified → Consider eligibility for thrombolysis/thrombectomy
   • If no large vessel occlusion → Consider additional imaging based on clinical suspicion:
     • MRI with DWI for small or posterior circulation infarcts
     • Cardiac evaluation (ECG, echocardiogram) for embolic source
     • Carotid imaging if not already obtained with CTA

By following this systematic approach, clinicians can rapidly distinguish between hemorrhagic and embolic strokes, allowing for appropriate treatment decisions and improved patient outcomes.