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Hyperdense MCA sign

Dr MT Niknejad and Dr Jeremy Jones et al.

The hyperdense MCA sign (HMCAS) refers to the appearance of the middle cerebral artery (MCA) on CT.  It has been associated with poor outcome, although this is by no means established.5

Radiographic features

There is increased attenuation of the proximal portion of the MCA and it is often associated with thrombosis of the M1 MCA segment. It is one of the early signs of ischaemic stroke : MCA infarct. 

The same pathological process can give an MCA dot sign when seen end on.

The sign is typically seen within 90 minutes of the ischemic event, and thus, it is very important for radiologists to recognize this sign. It can save the patient in 'golden hour' of thrombolysis (3 hours for intravenous tPA, and 6 hours for intra-arterial thrombolysis). This sign has approx. 100% sensitivity, however only 30% specificity. 

It is usually associated with another important sign of acute ischaemia - insular ribbon sign.

Differential diagnosis

There are occasional reports of a hyperdense MCA sign seen with HSV encephalitis 4.

False-positives : (asymptomatic patients - usually bilateral)

  • high haematocrit
  • calcified atherosclerotic disease5

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