The “Dot sign” is one of the early signs of acute MCA territory infarction.
Corresponds to a punctate hyperdensity on CT and hyperintensity FLAIR or T1w MRI images in the Sylvian fissure.
Represents thrombotic material in the M2 and M3 segments of the MCA.
During such an acute stage of ischemia the adjacent brain parenchyma in the involved territory may show normal or faint high signal on FLAIR. The dot sign has a high specificity and high positive predictive value, but has low sensitivity.