Impact on stroke subtype diagnosis of early diffusion-weighted magnetic resonance imaging and magnetic resonance angiography

Background and Purpose-The purpose of the present study was to assess the d iagnostic usefulness of early diffusion-weighted MRI (DWI) and MR angiograp hy (MRA) in patients with ischemic stroke. Past approaches to stroke diagno sis required a series of diagnostic tests over several days of hospitalizat ion. New magnetic resonance methodologies that include DWI and MRA may allo w more rapid characterization of stroke pathophysiology. However, no previo us study has assessed the impact on formal stroke subtype diagnosis of earl y imaging with DWI/MRA. Methods-We analyzed 46 consecutive patients with acute ischemic stroke who underwent DWI/MRA within 24 hours of admission. Initial diagnoses were rend ered with use of the 2 most widely used formal stroke subtype classificatio n schemes, the TOAST and the Oxfordshire methods, which were applied to pat ients after CT/conventional MRI but before DWI/MRA, Modified TOAST and Oxfo rdshire diagnoses were then rendered based on the results of day 1 DWI, MRA , and DWI plus MRA. Final TOAST/Oxfordshire diagnoses at discharge were tak en as the gold standard. Results-Compared with final diagnoses, pre-MRI: TOAST diagnoses matched fin al diagnoses in 48%, improving to 83% after DWI alone, 56% after MRA alone, and 94% after DWI plus MRA. For the TOAST diagnostic subtypes of large-ves sel atherothromboembolism and small-vessel disease, pre-MRI diagnoses match ed final diagnoses in 56% and 35% of patients, respectively, improving to 8 9% and 100% after DWI/MRA. Pre-MRI Oxfordshire diagnoses matched final diag noses in 67% of patients, improving to 100% after DWI. Conclusions-The use of DWI/MRA within 24 hours of hospitalization substanti ally improves the accuracy of the diagnosis of early ischemic stroke subtyp e. When initial management and clinical trial eligibility decisions are inf luenced by stroke subtype, day 1 multimodal MRI is advantageous as a guide to therapy.