Abstract
Imaging has become a cornerstone of stroke management, translating pathophysiological knowledge to everyday decision-making. Plain computed tomography is widely available and remains the standard for initial assessment: the technique rules out haemorrhage, visualizes the occluding thrombus and identifies early tissue hypodensity and swelling, which have different implications for thrombolysis. Based on evidence from positron emission tomography (PET), however, multimodal imaging is increasingly advocated. Computed tomography perfusion and angiography provide information on the occlusion site, on recanalization and on the extent of salvageable tissue. Magnetic resonance-based diffusion-weighted imaging (DWI) has exquisite sensitivity for acute ischaemia, however, and there is increasingly robust evidence that DWI combined with perfusion-weighted magnetic resonance imaging (PWI) and angiography improves functional outcome by selecting appropriate patients for thrombolysis (small DWI lesion but large PWI defect) and by ruling out those who would receive no benefit or might be harmed (very large DWI lesion, no PWI defect), especially beyond the 3-hour time window. Combined DWI–PWI also helps predict malignant oedema formation and therefore helps guide selection for early brain decompression. Finally, DWI–PWI is increasingly used for patient selection in therapeutic trials. Although further methodological developments are awaited, implementing the individual pathophysiologic diagnosis based on multimodal imaging is already refining indications for thrombolysis and offers new opportunities for management of acute stroke patients.
Highlights
In the present era of thrombolysis, of specialized acute stroke units and of endovascular and neurosurgical interventions, imaging has become a cornerstone of modern stroke management
Despite the use of clinical exclusion criteria [72], the treatment carries a risk of around 6–7% of thrombolysis-associated symptomatic haemorrhage; the emerging role of imaging in this acute setting, beyond exclusion of intracranial haemorrhage and subarachnoid haemorrhage, is to identify and exclude that subgroup of patients who are unlikely to benefit and may be harmed by recombinant tissue plasminogen activator, in turn reducing the number needed to treat
Observing hyperperfusion, if early oedema is demonstrated by computed tomography (CT) or magnetic resonance imaging (MRI), may provide a rationale for treating arterial hypertension since some experimental studies suggest that hyperperfusion in necrotic tissue may promote the development of malignant brain swelling
Summary
In the present era of thrombolysis, of specialized acute stroke units and of endovascular and neurosurgical interventions, imaging has become a cornerstone of modern stroke management. Despite the use of clinical exclusion criteria [72], the treatment carries a risk of around 6–7% of thrombolysis-associated symptomatic haemorrhage; the emerging role of imaging in this acute setting, beyond exclusion of intracranial haemorrhage and subarachnoid haemorrhage, is to identify and exclude that subgroup of patients who are unlikely to benefit and may be harmed by recombinant tissue plasminogen activator (rt-PA), in turn reducing the number needed to treat. The Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) study used MRI to evaluate treatment with alteplase 3–6 hours from stroke onset, and demonstrated a better clinical response among patients with small DWI and the presence of mismatch on MR than in other subgroups, including the ‘matched’ DWI–PWI and the small DWI and PWI lesion subgroups. Observing hyperperfusion, if early oedema is demonstrated by CT or MRI, may provide a rationale for treating arterial hypertension since some experimental studies suggest that hyperperfusion in necrotic tissue may promote the development of malignant brain swelling
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