Figure 1

61 year old male presenting with left facial droop and dysarthria. Initial imaging studies were performed 6 hours after witnessed onset of speech difficulties. However, patient noted symptoms suggestive of facial weakness 12 hours prior to imaging. A &B. CTA demonstrates a proximal right MCA occlusion (white arrows). C &D. Initial DWI shows multiple punctate foci of diffusion abnormality consistent with a small acute infarct. E &F. Time to peak (TTP) MR perfusion map demonstrates a large volume of underperfused area involving the majority of the right MCA territory and consequently a large diffusion/perfusion mismatch. The patient did not undergo thrombolytic therapy because of the uncertain time between stroke onset and presentation. G &H. Follow-up MRI shows an infarction involving the majority of the right MCA territory. Whole brain map volume measurements for this patient are: DWI: 2.1 ml; MTT: 117 ml (mismatch: 115.4 ml); TTP: 28 ml (mismatch 25.9 ml).