What is the first-line imaging modality in the emergency department to distinguish hemorrhagic from ischemic stroke?

• A. MRI with diffusion weighting
• B. Lumbar puncture
• C. Non-contrast head CT
• D. CT angiography

Answer: (C)

In acute stroke evaluation, the priority is rapidly determining whether there is bleeding in the brain, because a bleed changes both prognosis and treatment. The quickest and most widely available test to accomplish this is a non-contrast head CT. It can detect acute intracranial hemorrhage and rule out bleed, enabling immediate decisions about reperfusion therapy for ischemic stroke without delay or the risks associated with contrast.

MRI with diffusion weighting is indeed highly sensitive for identifying early ischemia, but it typically takes longer, may be less accessible in the emergency setting, and can delay treatment. Lumbar puncture isn’t used to distinguish stroke type in the acute ED setting because it takes additional time and is invasive, and CT angiography, while valuable for assessing vascular occlusion or aneurysm, is usually added after the initial non-contrast CT if more detail about vessels is needed.

Thus, the first-line imaging modality to differentiate hemorrhagic from ischemic stroke in the emergency department is a non-contrast head CT.