Legend Axial unenhanced CT images show a hyperdense left middle cerebral artery.

> Legend FLAIR (upper left) shows some slightly bright non-specific foci in the white matter and heterogeneous signal in the left middle cerebral artery. On the MR angiogram (lower left) no flow signal is evident in the left middle cerebral artery. The diffusion weighted images (DWI - upper right) and the apparent diffusion coefficient (ADC - lower right) maps show restricted diffusion in the left lentiform nucleus and corona radiata.

Legend The perfusion images reveal that flow in the left middle cerebral artery territory is slower and decreased compared to the left. Arrival (time to peak) and passage (mean transit time) of contrast in the left MCA territory is delayed and the cerebral blood volume (area under the curve) is smaller. These abnormalities extends to a broader area than the diffusion abnormalities, which indicates that there is tissue at eminent risk (penumbra) for infarction. This patient could benefit from rTPA if the clot can be lysed and perfusion restored to the ischemic area.

Legend Unenhanced CT 24h later shows marked hypodense infarction at the same locations of restricted diffusion shown on the diffusion-weighted images. The surrounding brain shows some low-density edema but no additional infarction. Key words: stroke vascular infarction ischemia mri diffusion perfusion dwi pwi

Brain Diagnosis: Middle cerebral ischemia with diffusion/perfusion mismatch