Noncontrast CT of the brain is often used to evaluate patients with stroke-like symptoms, but is often normal or shows very subtle findings early in acute ischemic stroke.
One clue of acute ischemic stroke, shown above, is the "Hyperdense MCA Sign". The right Middle Cerebral Artery appears denser in its proximal course than the contralateral side. In this head CT, although it is not visualized in this CT slice, the contralateral MCA is normal in density.
The increased vessel attenuation on CT is thought to be due to thrombus within the MCA lumen. Studies have shown a high specificity but low sensitivity of this sign as well as poorer prognosis in patients who present with stroke and a hyperdense MCA sign. A false positive hyperdense MCA sign may be seen with increase hematocrit and vascular calcification.
References Jha B, Kothari M. Pearls & Oysters: Hyperdense or pseudohyperdense MCA sign: A Damocles sword? Neurology 2009; 72: e116-e117.
Pettiti N. The hyperdense middle cerebral artery sign. Radiology 1998; 208:687–688.
This "EM Lightbox" case was authored by guest blogger, Dr. Eric Silman.