Benjamin Friedrich

Until recently, decisions on stroke therapy were based solely on clinical assessment. Only noncontrast CT was needed to rule out intracranial hemorrhage or large infarction to treat the patients with intravenous tPA. Founding the treatment decision using only the clinical evaluation and NCCT was sound practice at the time of the initial studies testing the safety and efficacy of IV tPA, but still there are some difficulties in the decision-making process.

First, patients suffering from “stroke mimics” like seizures receive a potentially harmful treatment. This dilemma is mainly caused by the use of NCCT alone, without the now nearly ubiquitous possibility of assessing vascular status by way of CT angiography. One consequence is that patients without a proven vessel occlusion are treated.

Second, patients might be treated even though their chances of a good clinical outcome are very small, may it be due to their occlusion site and the lack of sufficient collaterals, their clot burden, or other factors contributing to their nonresponse to IV tPA. With the development of more sophisticated intra-arterial (IA) stroke therapy methods, especially the introduction of stent-retriever-based mechanical thrombectomy, the need for more advanced imaging tools became more and more apparent.

There are different conceivable approaches in this regard. The use of stroke MRI is a very promising method to visualize the infarction with high sensitivity, and many studies show the reliability of different MRI-based protocols like the diffusion/perfusion mismatch or the DWI/FLAIR mismatch concepts. Although these MRI-based methods are very elegant and sensitive, they suffer from a few core problems: 1) MRI is usually time-consuming, and time is brain; 2) MRI is not available in every center 24 hours per day, 7 days a week; 3) not all patients, especially patients with stroke, are eligible for MRI (compliance, metal implants, pacemakers, and so on). Therefore, another imaging modality that has been used for many years in addition to NCCT and CTA, to gather more information, is CT perfusion. CTP is a very powerful tool to visualize both the infarct core and the potentially salvageable penumbra in a very fast and reliable manner. Nearly all patients, except those who are severely agitated, can be scanned with this imaging method.

Thus, the aim of our study was to investigate the fate of the penumbra after mechanical thrombectomy, by analyzing prestroke CTP maps and the development of infarction and clinical course over time in correlation with endovascular treatment. We found that acute ischemic stroke treatment with stent-retriever-based endovascular mechanical recanalization and subsequent fast and lasting cerebral reperfusion can result in the rescue of a large amount of endangered brain tissue, with a highly significant correlation to the clinical improvement of the patients.

To further improve the outcome in our patients with a potentially devastating ischemic stroke, we need to develop individualized therapeutic models to decide which therapy—eg, just IV tPA, or IV tPA in combination with IA therapy—is the best option.

Read this article at AJNR.org …