MCA ischemic stroke - added value of CTA source image ASPECTS
Sudden onset somnolence and left-sided hemiparesis affecting face and extremities that developed 3 hours before presentation.
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In the noncontrast CT a hyperdense artery sign can be observed, involving the terminal part of the right internal carotid artery and the M1 segment of the right medial cerebral artery. The insula, head of caudate, and the lentiform nucleus appear hypodense, and blurred ipsilaterally. The ASPECTS score based on the noncontrast scan is therefore: 7.
In the CT angiography the right ICA and the right MCA appear completely occluded.
The postcontrast, angiography source image scan the supply area of the right MCA appears almost completely hypodense, corresponding to a CTA-SI ASPECTS score of 0, indicating a bleak prognosis in sharp contrast to the ASPECTS based on the noncontrast acquisition.
In the affected hemisphere only a few vessels are visible in the subsequent multiphase scans in any phase, corresponding to a very poor mCTA collateral score of 0-1.
The ASPECTS score in noncontrast brain CT is routinely used assess prognosis and the potential of endovascular intervention in ischemic MCA stroke. However it is much more prone to interobserver variability, and - as demonstrated by this case - far more likely to underestimate the extent of damage than CTA-SI ASPECTS, which is essentially the same scoring system applied to brain window and kernel reconstructions generated from the source images of multiphase CT angiography. It is therefore recommended to generate and evaluate brain window CTA source images whenever an angiography is performed in suspected acute stroke.