Core/penumbra mismatch

The results of the 2008 European Cooperative Acute Stroke Study (ECASS 111) expanded the 3-h time window for IV thrombolysis and revealed that although safe and effective up to 4.5 h after stroke onset, treatment benefits roughly one-half as many patients as those treated within 3 h [2, 158, 159]. Hence, the ratio between the hemorrhagic risk of treatment and the potential clinical benefit of treatment becomes a more critical consideration as the time window for therapy is expanded with newer IV and lA techniques. It is the mismatch between the size of the infarct core (proportional to hemorrhagic risk) and the size of the ischemic penumbra (proportional to potentially salvageable tissue), as determined by CTP, that provides an imaging measure of this risk-to-benefit ratio. Evidence suggests that core/penumbra mismatch may persist up to 24 h in some patients [160,161]. 

Fig. 5.9 Prediction of infarct growth. A 65-year-old man, improving clinically at 5 h postictus, was monitored in the Neurology ICU based on his labile blood pressure, a fixed left M2 occlusion on CTA, and a significant core/penumbra mismatch on CTP/MRP. His 24-h follow-up DWI showed a small infarction. However, 24 h after cessation of hypertensive therapy there was infarct growth into the region of penumbra. Admission CTA (top) CTP (CBV/CBF/ MTT) at 4.5 h second row) MR-perfusion weighted imaging (MR-PWI) (CBV/CBF/MTT) at 5.25 h (third row) DWI at 24 h (fourth row) and follow-up DWI at 48 h (bottom). The CTP and MR-PWI demonstrate a mismatch between the CBV (no abnormality) and the CBF/MTT penumbra (arrows). After cessation of hypertensive therapy, the DWI abnormahty grows into the region predicted by the CBF/MTT maps...

Schaefer PW, Barak ER, KamaUan S et al (2008) Quantitative assessment of core/penumbra mismatch in acute stroke. CT and MR perfusion imaging are strongly... 

Fig. 3.1a,b. a The ischaemic penumbra. The perfusion (PI) lesion delineates the extent of hypoperfusion and the diffusion (DWI) lesion outlines the infarct core. The difference between the two lesions (perfusion-diffusion mismatch) represents the ischaemic penumbra, tissue at risk of progression to infarction, b Patient imaged at 3 h after onset of left hemiparesis and neglect with large PI (time to peak - TTP) lesion and smaller DWI lesion. At day 3 reperfusion has not occurred and the infarct core (diffusion lesion) has expanded greatly into the region of acute perfusion-diffusion mismatch. This is consistent with the perfusion-diffusion mismatch area representing the ischaemic penumbra... 

Fig. 4.12. Mismatch concept of diffusion lesion (smaller) and perfusion deficit (larger) in human territorial brain infarction. Acute MCA territory ischemia/oligemia with a smaller, centrally located diffusion disturbance showing the relationship between infarct core, ischemic penumbra and changes in DWI and PI. DWI, diffusion-weighted imaging PI, perfusion imaging ADC, apparent diffusion coefficient ATP, high energy phosphates MCA, middle cerebral artery...

As described in the previous chapter on the ischemic penumbra, a patient with significant neurological deficit (NIHSS > 10), the finding of an ICA or proximal MCA occlusion and a small infarct core (<70-100 mL), very likelyhasavolumeofhypoperfused, symptom-producing tissue at risk that is at least 50% greater than the core volume. This concept was initially proposed as the diffusion-clinical mismatch [108, 109], and is based on the fact that the occlusion, core, and penumbra are not independent variables, but are related to each other by the collateral circulation. If one can identify two of the... 

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