Hyperdense MCA Sign

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Diagnosis Definition

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

Imaging Findings

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)

Pearls

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

References

Petitti N. The hyperdense middle cerebral artery sign. Radiology 1998; 208:687-688
Beauchamp NJ, Barker PB, Wang PY, van Zijl PCM. Imaging of acute cerebral ischemia. Radiology 1999: 212:307-324

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