How well can an intracranial bleed or hematoma be visualized on a computed tomography (CT) head scan with versus without contrast?

Intracranial Hemorrhage Visualization: Non-contrast CT vs Contrast-enhanced CT

Non-contrast CT is superior to contrast-enhanced CT for visualizing intracranial hemorrhage or hematoma, as contrast administration may obscure subtle hemorrhages due to enhancement. 1

Imaging Approach for Intracranial Hemorrhage

First-line Imaging

• Non-contrast head CT is the gold standard and first-line imaging test for detecting acute intracranial hemorrhage 1, 2
  • Highly sensitive for acute hemorrhage
  • Rapid acquisition time
  • Can identify location, size, and mass effect
  • Acute hemorrhage appears hyperdense (50-100 Hounsfield units)
  • Recommended by the American College of Radiology (ACR) for evaluation of head trauma 2

Why Contrast May Obscure Hemorrhage

• Contrast enhancement can mask or obscure subtle hemorrhages 1
• Administering contrast before initial non-contrast CT can lead to missed diagnoses 1
• The use of contrast-enhanced head CTs as a first-line test in acute settings does not add significant value over non-contrast head CT examinations 2

When Contrast-Enhanced CT Is Appropriate

• After hemorrhage has been identified on non-contrast CT
• When evaluating for underlying structural lesions such as:
  • Intracranial infection
  • Tumor
  • Inflammatory pathologies 2
• When isodense subdural hematoma is suspected, especially in anemic patients 1

Advanced Imaging Considerations

Follow-up Imaging Options

• If vascular abnormality is suspected:

  • CT angiography (CTA) should be performed after non-contrast CT 1
  • CTA has >90% sensitivity and specificity for identifying vascular lesions 1

• For better characterization of hemorrhage:

  • MRI with gradient echo (GRE) or susceptibility-weighted imaging 1
  • MRI is more sensitive than CT for:
    • Prior hemorrhage
    • Small bleeds (particularly in posterior fossa or brainstem)
    • Subacute and chronic subdural collections 1

Special Considerations

• Small hemorrhages in the posterior fossa may be missed on non-contrast CT 1
• Chronic subdural hematomas appear hypodense on CT with density similar to CSF 1
• A common practice is to perform a non-contrast screening head CT followed by MRI brain examination with and without contrast when needed 2

Clinical Implications

• Accurate detection of intracranial hemorrhage is critical for patient management and outcomes
• Misdiagnosis due to improper imaging technique can lead to delayed treatment and poorer outcomes
• For patients with suspected stroke, focal neurologic deficit, seizure, head trauma, or headache, non-contrast CT remains the initial imaging study of choice 2

In conclusion, non-contrast CT should always be performed first when intracranial hemorrhage is suspected, with contrast-enhanced studies reserved for specific follow-up indications after hemorrhage has been identified or ruled out.