The diagnostic value of perfusion-weighted magnetic resonance imaging as an adjunct to routine magnetic resonance protocols for adults presenting with acute ischaemic stroke: A structured literature review

Abstract

Abstract Background: Stroke is one of most burdensome neurological conditions affecting young and older adult populations, worldwide, and notably, it has remained one of the leading causes of disability and premature mortality within its disease category. Efforts to reduce the burden of stroke have focused upon the early reperfusion therapies and the timeliness and accuracy of diagnosis as can only be reliably ascertained using cross-sectional imaging studies. In recent times, there has been growing recognition that perfusion-weighted MRI offers a significant advantage in diagnosing and characterising the ischaemia induced by stroke as it can elicit diffusion-perfusion deficits that may benefit from treatment to prevent infarction. Aim: This structured literature review sought to explore the diagnostic utility and accuracy of perfusion-weighted MRI as compared to other MRI protocols. A search for relevant literature was performed in June 2020 using MEDLINE, EMBASE and the Cochrane library and articles were limited to English language and publication in the last 15 years. Eligible articles were appraised using the QUADAS-2 framework and given marked inter-study heterogeneity, the diagnostic outcomes were analysed using a narrative approach. Results: A total of 10 studies were suitable for review and these were retrospective (n=9) and prospective studies (n=1), which were found to observe a moderate to high risk of bias. The results revealed that in most cases, perfusion-weighted MRI offers superior diagnostic capabilities when compared to other forms of MRI with a sensitivity as high as 100% and ability to detect significant diffusion-perfusion mismatches, which can significantly influence management and in turn, neurological outcomes. However, one limitation of perfusion-weighted MRI is that it can over-estimate the degree of oligaemia and ischaemia in brain tissue and indeed, ischaemia does not always progress to infarction and thus, treatment in such cases would be unnecessary and expose patients to a number of adverse effects. Despite this, it was demonstrated that perfusion-weighted MRI could substantially benefit the care for a select number of cases including the better characterisation of posterior circulation strokes – a limiting factor of diffusion-weighted MRI, and on average, being consistent in detecting 20-50% mismatches. Conclusion: Overall, the findings of this review have a number of important implications for current radiological practice and ischaemic stroke guidelines, which include that perfusion-weighted MRI should be considered for routine use over other MRI protocols and as a potential primary alternative to CT given the avoidance of ionising radiation and that treatment outcomes are not affected by differences in acquisition times. Finally, future research should focus upon evaluating multimodal MRI as this may offer addition diagnostic and prognostic benefits by accounting for the limitations of all MRI protocols used in current practice.