A 46-year-old man with a history of hyperlipidemia but neither history of recent trauma nor headache suddenly developed left hemiparesis. He was alert and had no known neurological deficits on admission to the emergency department. Cranial computed tomographic images revealed high attenuation of the right middle cerebral artery (MCA) (Figure, A). Magnetic resonance (MR) imaging found no fresh infarcts, and MR angiography revealed severe stenosis of the right MCA (Figure, B). Three-dimensional–computed tomographic angiography showed tapering stenosis of the right MCA horizontal segment, which is indicative of arterial dissection (Figure, C). A transient ischemic attack resulting from arterial dissection rather than atherosclerosis of the right MCA was suspected, but no definitive diagnosis could be reached. Anticoagulant therapy was started for near occlusion. We applied a unique (to our knowledge) MR imaging technique on day 5 to evaluate the surface of the MCA. The technique required 2-cm-thick, heavily T2-weighted coronal imaging (time to repetition = 10 000; echo time = 548) parallel to the sylvian vallecula with gray-scale reversal during postprocessing. We refer to this procedure as sylvian vallecula-parallel anatomic scanning (SyPAS). The SyPAS findings confirmed fusiform dilation of the right MCA horizontal segment (Figure, D). Because the MR angiographic images were not equal to those of SyPAS because of partial thrombosis within the lesion, transient ischemic attack owing to MCA dissection was definitively diagnosed.
Various types of middle cerebral artery (MCA) horizontal segment imaging. A. Brain computed tomographic imaging shows increased attenuation of the right MCA (arrow). B. Magnetic resonance angiography shows severe stenosis of the right MCA (arrow). C. Tapering stenosis of the right MCA visualized by 3-dimensional computed tomographic angiography (arrow). D. Fusiform dilation of the surface of the right MCA (arrow) detected by sylvian vallecula-parallel anatomic scanning.
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