Answer
Following acute ischemic stroke, treatment measures to induce reperfusion must be implemented within a recognized time frame ,which means that timely recognition of this condition is vital. This involves bedside assessments followed by appropriate imaging studies including MRI. Stroke mimics including metabolic, traumatic, migranous, neoplastic, convulsive, and psychiatric disorders account for 3-30% of patients presenting with acute neurological deficits. [11] A rapid MRI sequence may be used to select patients for rapid diagnosis and treatment. [12] Such MRI sequence typically incorporates diffusion weighted sequence, FLAIR and gradient sequence, requiring less than 10 minutes, and have been successfully incorporated into acute stroke management protocol.
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Magnetic resonance imaging in acute stroke. Left: Diffusion-weighted MRI in acute ischemic stroke performed 35 minutes after symptom onset. Right: Apparent diffusion coefficient (ADC) map obtained from the same patient at the same time.
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Magnetic resonance imaging in acute stroke. Left: Perfusion-weighted MRI of a patient who presented 1 hour after onset of stroke symptoms. Right: Mean transfer time (MTT) map of the same patient.
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Magnetic resonance imaging in acute stroke. Diffusion-perfusion mismatch in acute ischemic stroke. The perfusion abnormality (right) is larger than the diffusion abnormality (left), indicating the ischemic penumbra, which is at risk of infarction.
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The diffusion-weighted MRI reveals a region of hypointensity in the distribution of the right middle cerebral artery. Flanking the anterior and posterior regions of this abnormality are regions of hyperintensities, which represent regions of new infarct. The contiguity of these regions suggests that they are extensions of the old infarct.