A Cochrane review [Abstract] 1 included 8 studies with a total of 306 subjects with acute stroke. Studies either compared diffusion-weighted MRI (DWI) and computed tomography (CT) in the same patients for detection of ischaemic stroke or examined the utility of MRI for detection of haemorrhagic stroke and had imaging performed within 12 hours of stroke onset. Ischaemic stroke was studied in 7 trials and haemorrhagic stroke in 2 trials. Three studies clearly reported stroke severity. In 4 studies patients had middle cerebral artery stroke; 2 studies predominantly enrolled patients with anterior circulation stroke and one study did not select the type of stroke. Amongst the patients subsequently confirmed to have acute ischaemic stroke (161/226), for DWI sensitivity was 0.99 (95% CI 0.23 to 1.00) and specificity 0.92 (95% CI 0.83 to 0.97). For CT sensitivity was 0.39 (95% CI 0.16 to 0.69) and specificity 1.00 (95% CI 0.94 to 1.00). Studies on haemorrhagic stroke reported high estimates for diffusion-weighted and gradient-echo sequences but had inconsistent reference standards and overall estimates were not calculated.
Comment: The quality of evidence is downgraded by study quality (lack of blinding), indirectness (studies included mostly mild strokes), imprecise results (limited study size for each comparison) and inconsistency (heterogeneity in populations studied).
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