Patients with Diffusion-Perfusion Mismatch on Magnetic Resonance Imaging 48 Hours or More After Stroke Symptom Onset: Clinical and Imaging Features

BACKGROUND: Abnormalities in diffusion-weighted (DWI) and perfusion-weighted (PWI) magnetic resonance imaging (MRI) are thought to reflect the presence of brain tissue at risk for ischemic stroke. Many patients with acute ischemic stroke have a mismatch pattern in which the PWI volume is larger than the DWI lesion. This mismatch typically resolves over 24-48 hours. Little is known about the presence of DWI-PWI mismatch in later stages of stroke. METHODS: This is a retrospective study of 122 patients admitted with a diagnosis of acute ischemic stroke who had DWI and PWI abnormalities on studies performed within 7 days of onset of symptoms. Patients were divided into two groups: those with MRI performed <48 hours and those with MRI performed >or=48 hours from onset of symptoms. RESULTS: Among 42 patients with MRI performed >or=48 hours after onset of stroke symptoms, 15 of 42 (36%) showed a mismatch pattern, compared to 45 of 80 (56%) in the <48 hours group (P < 0.05). Most of the patients in the >or=48 hours group with mismatch had large artery occlusive disease and many had neurological fluctuations. A subset of these patients were treated with induced hypertension and showed clinical improvement. CONCLUSIONS: Some patients have persistent DWI-PWI mismatch up to several days after stroke onset. Further studies are needed to determine if these patients should be candidates for reperfusion therapy.