Imaging in Acute Ischemic Stroke : Relevance to Management

With the advent of thrombolytic therapy in the treatment of acute ischemic stroke, it has become increasingly important to identify the suitable patients for whom such therapy may be useful. The success of reperfusion therapy depends on salvaging ischemic tissue at risk (penumbra). Imaging techniques continue to evolve. MRI with diffusion weighted and perfusion imaging can identify the penumbra (diffusion-perfusion mismatch). MR Angiography provides additional information about large and medium size vessel occlusion. However, MRI is limited by its lesser availability and slower acquisition times. Ultrafast perfusion CT scans are more widely available and seem capable of identifying the ischemic tissue at risk. Newer techniques of perfusion CT and triphasic perfusion CT are becoming more refined and along with CT Angiography provide information not only of the penumbra but also of large vessel occlusion. Patients with large vessel occlusion of the internal carotid and middle cerebral artery are best treated by intra-arterial thrombolytic therapy whereas branch occlusions are suitable for intravenous thrombolysis. Patient selection, based on the present and evolving MRI and CT techniques would provide a more rational application of treatment (greater chances of reperfusion and minimizing the possibility of symptomatic intracerebral hemorrhage).