Hyperdense MCA Sign

Diagnosis
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  • The hyperdense middle cerebral artery (MCA) sign is an indicator of acute occlusive thrombosis and ischemic stroke; the sign occurs during the first hours of stroke
  • The sign has high specificity but limited sensitivity
  • The hyperdense vessel sign can also be seen in the MCA branches (MCA dot sign) and with basilar thrombosis
  • The hyperdense MCA sign is seen on noncontrast CT as increased density within the MCA
  • Associated findings include the “insular ribbon sign” (low attenuation in the insula), the “basal ganglia sign” (focal low attenuation in the basal ganglia), blurring of gray-white matter differentiation, and sulcal effacement (loss of the normal sulcal space with apposition of the gray matter, reflecting cortical swelling)
  • The MRI equivalent of the hyperdense MCA sign is absence of flow void in the MCA on T2-weighted imaging and prominent decreased “blooming” signal within the vessel on GRE or susceptibility-weighted imaging (known as the “susceptibility vessel sign”)
  • Detection of signs of early ischemia in the brain parenchyma can be enhanced with the use of narrow window width and center level settings, which accentuates the gray-white matter contrast
  • Comparison with the normal side is helpful in the detection of subtle signs of acute ischemia
  • Perfusion-weighted CT imaging can help detect completed infarcts as well as tissue at risk
  1. Petitti N. The hyperdense middle cerebral artery sign. Radiology 1998; 208:687-688
  2. Beauchamp NJ, Barker PB, Wang PY, van Zijl PCM. Imaging of acute cerebral ischemia. Radiology 1999: 212:307-324