MR imaging of middle cerebral artery occlusion without cerebral infarction.

Magnetic resonance (MR) images of 12 patients with angiographically proven middle cerebral artery (MCA) occlusion were analyzed, retrospectively. In three of the 12 patients, cerebral infarctions related to the MCA occlusions were not evident. Two of the three patients were cases of atherosclerotic occlusion and the remaining patient had an acute thromboembolism. In all of the occluded M1 portions of the MCA the flow void was absent and there were isointense linear structures, with or without a hyperintense component in the Sylvian vallecula, on T1-weighted images. For nine of the 12 patients, the absence of flow void in the ipsilateral Sylvian fissure was evident on the T2-weighted images. Therefore, even in cases with no evidence of a cerebral infarction, the presence of flow void in the Sylvian vallecula and Sylvian fissure must be searched for in routine reviews of MR images. If MR imaging can be obtained on an emergency basis, appropriate interventional therapy may be immediately initiated.