Korean J Radiol.  2015 Apr;16(2):372-390. 10.3348/kjr.2015.16.2.372.

Imaging-Based Management of Acute Ischemic Stroke Patients: Current Neuroradiological Perspectives

• Na DG
• Sohn CH
• Kim EY

• KMID: 2070182
• DOI: http://doi.org/10.3348/kjr.2015.16.2.372

Abstract

Advances in imaging-based management of acute ischemic stroke now provide crucial information such as infarct core, ischemic penumbra/degree of collaterals, vessel occlusion, and thrombus that helps in the selection of the best candidates for reperfusion therapy. It also predicts thrombolytic efficacy and benefit or potential hazards from therapy. Thus, radiologists should be familiar with various imaging studies for patients with acute ischemic stroke and the applicability to clinical trials. This helps radiologists to obtain optimal rapid imaging as well as its accurate interpretation. This review is focused on imaging studies for acute ischemic stroke, including their roles in recent clinical trials and some guidelines to optimal interpretation.

Keyword

Stroke; Brain infarction; Multidetector-row computed tomography; Magnetic resonance imaging

MeSH Terms

Brain/blood supply/radiography
Brain Infarction/*radiography/*therapy
Cerebral Angiography/methods
Diagnostic Imaging
Diffusion Magnetic Resonance Imaging/*methods
Fibrinolytic Agents/*therapeutic use
Humans
Intracranial Hemorrhages/diagnosis/radiography
Fibrinolytic Agents

Figure

• 

  Fig. 1 Early ischemic changes on unenhanced head CT (3 different patients). Unenhanced head CT shows areas of loss of gray/white matter differentiation involving right insula and right temporal lobe (arrows) (A). 83-year-old female with last-seen normal time of approximately midnight underwent CT next day at 8 AM. Attenuation of lesion in right frontal lobe (arrow) is slightly lower than that of contralateral white matter but higher than that of cerebrospinal fluid, suggestive of frank hypodensity (B). Unenhanced CT demonstrates focal gyral swelling with obliteration of adjacent sulci on left (arrows) (C). Note there is no loss of gray/white matter differentiation.

• 

  Fig. 2 Alberta Stroke Program Early CT (ASPECT) Score. ASPECT scoring system is applied to both unenhanced CT and diffusion-weighted imaging (DWI). When this system was introduced, it measured scores only at basal ganglia and supraganglionic level. However, it has subsequently evolved to assess entire brain. Normal CT or DWI is scored 10 (3 from subcortical regions and 7 from cortical regions). One point is deducted for each area with abnormality (early ischemic change on CT or lesion showing diffusion restriction). In this particular patient, acute infarct is noted in right M1, M2, M3, M5, I, and L on DWI, yielding ASPECT score of 4. However, it is suggested that right M6 is also affected. This discrepancy may be because ASPECT score does not have landmarks that separate M2 and M3, and M5 and M6. Early ischemic change is also suspected in similar regions on unenhanced head CT (arrows). However, DWI is more sensitive and reliable than unenhanced CT.

• 

  Fig. 3 Diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) mismatch in 76-year-old female. Last-seen normal time was at 11:00 PM. MRI was obtained on next day at 9:42 AM. Acute infarcts are noted in right middle cerebral artery territory on DWI. However, most DWI lesions do not show hyperintensity in same regions on FLAIR imaging, suggesting that patient had acute infarct within 3 hours.

• 

  Fig. 4 Hyperintense vessels on fluid-attenuated inversion recovery (FLAIR). MR angiography shows occlusion in right M1 segment. Hyperintense vessels are noted in branches of right middle cerebral artery on FLAIR images (arrows).

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  Fig. 5 Signs of clot and transmedullary vein involvement on susceptibility-weighted imaging (SWI) in patient with occlusion in right M1 segment. A. Time-of-flight MR angiography demonstrates occlusion in region of right distal M1 segment. B. Hypointense clot (arrowhead) is noted at corresponding region of right middle cerebral artery on SWI. C. Several hypointense transmedullary veins (arrows) are more conspicuously visualized on right on SWI.

• 

  Fig. 6 Favorable diffusion-weighted imaging-perfusion-weighted imaging (DWI-PWI) mismatch pattern (large penumbra with small infarct). A. TOF MR angiography demonstrates occlusion in region of right distal M1 segment. B, C. Lesion on DWI is limited to right insula (B), whereas areas of hypoperfusion (defined by Tmax ≥ 6 seconds [red] and Tmax ≥ 4 seconds [yellow]) are much larger than DWI lesion, representative of favorable DWI-PWI mismatch (C).

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