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Case Reports
. 2005 Sep;26(8):2027-9.

The hypodense artery sign

Thomas C Lee  1 , Eric S Bartlett, Allan J Fox, Sean P Symons
Affiliations
Case Reports

The hypodense artery sign

Thomas C Lee et al. AJNR Am J Neuroradiol. 2005 Sep.

Abstract

An acute intracranial embolus may be associated with a hyperdense artery sign on CT, related to acute thrombus within the affected artery, a phenomenon that is well known and has been extensively documented. We present an unusual case of a middle cerebral artery territory acute infarct with a hypodense artery on CT. The Hounsfield unit attenuation of the embolic lesion was fat density. CT angiography and MR imaging confirmed the fatty lesion to be within the middle cerebral artery.

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Figures

F<sc>ig</sc> 1.
Fig 1.
A 78-year-old woman who had undergone a mitral valve replacement. A–C, Axial images from the initial CT head scan obtained on the first postoperative day demonstrate an early left middle cerebral artery territory infarct. There is a fat attenuation filling defect (arrow, B) in the region of the proximal left middle cerebral artery trunk.
F<sc>ig</sc> 2.
Fig 2.
CT angiography axial image obtained 13 days postoperatively confirms that the fat attenuation lesion (arrow) is within the proximal left middle cerebral artery trunk.
F<sc>ig</sc> 3.
Fig 3.
Axial and coronal T1-weighted MR images obtained 49 days postoperatively without fat saturation (A,B) and with fat saturation (C,D). The images without fat saturation demonstrate the T1-hyperintense embolus (arrow) in the proximal left M1 trunk. After fat saturation, the T1 hyperintensity of the embolus is saturated (arrow), confirming its fatty composition. High-signal-intensity methemoglobin in the adjacent infarct is unchanged before and after fat saturation.
See this image and copyright information in PMC

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