====== Hyperdense artery sign ======

First described in the [[MCA]] in [[1983]]
((Gacs G, Fox AJ, Barnett HJM, et al. CT Visualization of Intracranial Thromboembolism. Stroke. 1983; 14:756–762)).
The cerebral vessel (usually the MCA) appears as high density on unenhanced CT

{{::hyperdense_artery_sign.png?300|}}

indicating intra-arterial clot ([[thrombus]] or [[embolus]])
((Tomsick TA, Brott TG, Olinger CP, et al. Hyperdense Middle Cerebral Artery: Incidence and Quantitative Significance. Neuroradiology. 1989; 31:312–315)).
Seen in 12% of 50 patients scanned within 24 hrs of stroke, and 34% of 23 very early CTs did to R/O hemorrhage. Sensitivity for MCA occlusion is low, but specificity is high (although it may also be seen with carotid dissection, or (usually bilaterally) with calcific atherosclerosis or high hematocrit
((Tomsick TA, Brott TG, Olinger CP, et al. Hyperdense Middle Cerebral Artery: Incidence and Quantitative Significance. Neuroradiology. 1989; 31:312–315)).
Does not have independent prognostic significance.
((Manelfe C, Larrue V, von Kummer R, et al. Association of Hyperdense Middle Cerebral Artery Sign With Clinical Outcome in Patients Treated With Plasminogen Activator. Stroke. 1999; 30: 769–772)).