Acute Stroke Diagnosis and Imaging

Initial Imaging Assessment

The primary goal of imaging in acute stroke is to distinguish between hemorrhagic and ischemic stroke, which is crucial for treatment decisions, as recommended by the American College of Radiology 1, 2
Non-contrast CT (NCCT) remains the most widely used initial imaging modality due to its rapid acquisition (seconds) and excellent sensitivity for detecting hemorrhage, with a sensitivity supported by the American Heart Association 3, 4
MRI with diffusion-weighted imaging (DWI) is more sensitive than NCCT for early detection of ischemic changes but should not delay treatment if not immediately available, according to the American Stroke Association 5, 6

For patients within 4.5-hour window (IV tPA candidates), either NCCT or MRI is recommended to exclude intracranial hemorrhage before IV tPA administration, as suggested by the American College of Cardiology 6
If MRI can be performed without delaying treatment, it offers superior sensitivity for detecting early ischemia, with evidence from the American Heart Association 6
Vascular imaging (CTA, MRA, or conventional angiography) is strongly recommended during initial evaluation for patients who are endovascular therapy candidates, as recommended by the American College of Radiology 2, 7

Non-contrast CT (NCCT) excludes hemorrhage, identifies early ischemic changes, and excludes stroke mimics, with evidence from the American Stroke Association 4, 6
CT Perfusion (CTP) differentiates between infarcted core and salvageable penumbra, and is essential for selecting patients beyond 6 hours from symptom onset, as suggested by the American College of Radiology 4, 6

Diffusion-weighted imaging (DWI) is most sensitive for early infarct detection, with evidence from the American Heart Association 4
Perfusion-weighted imaging identifies tissue at risk, with support from the American Stroke Association 3, 4

For patients beyond 6 hours from symptom onset, multimodal imaging with perfusion assessment is essential for treatment selection, as recommended by the American College of Cardiology 5
In TIA patients, multimodal MRI is preferred over NCCT due to higher sensitivity in detecting subtle lesions, with evidence from the American College of Radiology 1, 2
DWI positivity in TIA patients indicates higher risk for recurrent ischemic events, as suggested by the American Heart Association 2

Focusing solely on NCCT without vascular imaging may miss large vessel occlusions requiring endovascular therapy, with evidence from the American College of Radiology 2, 7
Delaying treatment for advanced imaging must be balanced against time-sensitive nature of reperfusion therapies, as recommended by the American Stroke Association 7