Narrow Window CTによる超急性期脳虚血所見

We report a new computed tomographic (CT) finding of hyperacute ischemic stroke. We examined the CT findings of patients with acute ischemic stroke within 3 h of onset by using a very narrow CT window width. The CT number (Hounsfield unit, HU) of the ischemic area was decreased by only 1 or 2 units. The areas of decreased CT number were larger than the hyperintense areas observed in magnetic resonance imaging diffusion-weighted images (MRI-DWI). These areas were not detected as so called “early CT signs” of acute ischemia on conventional CT. We examined 3 patients of hyperacute stroke, and treated them with tissue-plasminogen activator within 3 h of onset. Their narrow-window CT examination revealed low-density areas that were not detected in the conventional study. After arterial recanalization and resolution of ischemic symptoms, these low-density areas reduced and the CT number was normalized. When recanalization did not occur, these areas showed signs of infarction. A low-density area in a narrow-window CT study may be a hypo-perfused area and include reversible ischemic area (or penumbra).