Use of Imaging to Select Patients for Late Window Endovascular Therapy

Gregory W. Albers, MD


Stroke. 2018;49(9):2256-2260. 

In This Article

MRI Findings After Reperfusion

At stroke onset, early cytotoxic edema causes restricted water proton movement, which is reflected by an immediate decline in the ADC value. Reperfusion is associated with an increase in ADC values, even in regions of brain that are irreversibly injured (Figure 3). The magnitude of the rise in ADC values is variable and frequently is nonuniform within an individual ischemic lesion. Frequently, after reperfusion, the ADC increases to values >620×10−3 mm/s in part or all of the ischemic lesion. This increase in ADC typically does not indicate tissue salvage. Because of the variable rise in ADC after reperfusion, the volume of tissue with a low ADC frequently underestimates the ischemic lesion that is visible on the DWI or fluid-attenuated inversion recovery (FLAIR) after reperfusion has occurred. Therefore, after reperfusion, infarct volume should be assessed from the DWI or FLAIR maps rather than the ADC volumes.

Figure 3.

The first set of 3 images was obtained 2 hours after symptom onset in a patient with an acute right middle cerebral artery (MCA) occlusion. The top image, a FLAIR sequence is normal; however, the diffusion-weighted lesion (DWI) map, identifies regions of severe ischemia with low apparent diffusion coefficient (ADC) values adjacent to the right lateral ventricle (shown in pink). On the Tmax perfusion image, shown immediately below the DWI map, the green region corresponds to a large portion of the MCA vascular territory with severe hypoperfusion. Four hours after symptom onset, the patient experienced complete reperfusion of the MCA occlusion. After reperfusion, the ADC values (shown by the blue line) rise to levels above the ADC threshold (shown with a dotted yellow line) therefore the complete DWI lesion no longer has a low ADC (pink color almost disappears) but typically will still be visible as a bright lesion on both the DWI and FLAIR map.