Dense or hyperdense MCA (middle cerebral artery) sign is a well recognized sign of early ischemia and is associated with large infarctions in MCA territory.
Dense PCA sign is not so well recognized, however, it can be seen in about 35% of all cases of PCA territory infarction. It is typically located in ambient cistern, at ponto-mesencephalic junction, near pituitary stalk. In the CT images above, the dense PCA has been marked with yellow. Extensive infarction in PCA territory can be seen in the CT scan image on top.
Significance of dense PCA sign: If dense PCA sign is noted on CT, there is a significantly higher incidence of thalamic infarct. The size of infarct is most often larger rather than medium. There is also a higher risk of hemorrhagic transformation of the infarct. (Stroke, Feb 2016)