Stroke imaging in the age of thrombolysis

Summary Neuroimaging enables assessment of the vascular, morphological and physiological status of the brain; however, CT remains the principal modality in the investigation of hyperacute stroke. Recently published trials have proven the efficacy of intra-arterial therapy in ischaemic stroke secondary to large vessel occlusion. Imaging-based therapy selection can be used to select patients with a large vessel occlusion who would benefit from intra-arterial therapy, either as an adjunctive to intravenous thrombolysis or on its own in patients with contraindications to intravenous thrombolysis. Imaging is essential to exclude stroke mimics and to discriminate haemorrhagic and ischaemic stroke. Neuroimaging can enable accurate assessment of the vascular, morphological and physiological status of the brain. CT remains the principal modality in the investigation of hyperacute stroke, being accurate, quick and widely available. The use of CT angiography and/or CT perfusion has the potential to improve CT infarct detection and enable individualization of treatment strategy, although it would be inappropriate to place reliance on specific perfusion thresholds at present. The advent of diffusion- and perfusion-weighted imaging revolutionized stroke imaging with MRI. However, MRI is less readily available than CT, more time consuming and less well tolerated in acutely unwell patients, which in routine practice significantly limits its utility in hyperacute disabling stroke. Neuroimaging may be useful to identify patients in whom thrombolysis is relatively contraindicated and is essential to triage patients in whom intra-arterial (IA) therapy may be appropriate. Another group who may benefit are those with stroke of unknown time onset. Imaging-based therapy selection is the subject of much research. There have been five recently published trials which have proven the efficacy of IA thrombectomy. There is a clear link between recanalization and good outcome and high recanalization rates in all thrombectomy studies; however, good clinical outcomes are still dependent on rapid intervention.