Differences in the diagnostic accuracy of acute stroke clinical subtypes defined by multimodal magnetic resonance imaging

Background: Despite its importance for acute stroke management, little is known about the underlying pathophysiology when patients with acute stroke are classified using clinical methods. Objective: To examine the relation between the magnetic resonance defined stroke subtype and clinical stroke classifications using diffusion weighted imaging (DWI), perfusion weighted imaging (PWI), and angiographic magnetic resonance techniques. Methods: Consecutive patients with clinical syndromes consistent with acute anterior circulation stroke were assessed clinically within six hours of onset and scanned as soon as possible using multimodal magnetic resonance imaging (MRI). Patients were classified clinically into total or partial anterior circulation syndromes using the Oxford classification, or according the severity of the National Institutes of Health stroke scale (NIHSS) (severe > 15; mild/moderate < 15). At day seven, patients were classified by combining clinical course and MRI data as misdiagnosed, misclassified, suffering transient ischaemic attack, infarct with recanalisation, or infarction with persisting occlusion. Patients with occlusion were further divided on the basis of a large diffusion-perfusion mismatch. Results: 84 patients with clinical anterior circulation syndromes were studied. Using the NIHSS, 42 were mild to moderate (0-15) and 42 were severe (> 15). There were 42 with partial anterior circulation syndromes (PACS) and 42 with total anterior circulation syndromes (TACS). Patients with TACS or severe stroke were more likely to have actually suffered a stroke (Fischer's exact test, p = 0.01), to have a correctly classified stroke (chi(2) 28.2, p < 0.01), to have persisting occlusion (χ(2) 30.6, p < 0.01), and to have a large DWI-PWI mismatch (chi(2) 17.1, p < 0.01). Conclusions: There is more inaccuracy in patients presenting with acute PACS or clinically mild to moderate anterior circulation stroke than in those with TACS or severe acute stroke syndromes. The latter appear more likely to be the targets for acute stroke interventions, as they include a significantly higher proportion of patients with persisting occlusion and diffusion/perfusion mismatch.