Insular ribbon sign – refers to loss of the normal insular cortex grey-white differentiation and is one of the earliest imaging sign of middle cerebral artery territory infarction. The insular cortex is located along the Sylvian fissure overlying the external capsule where a ‘ribbon’ of normal cortex should be appreciable (red arrows). In the setting of MCA infarction, cytotoxic oedema leads to hypoattenuation such that the normal insular ribbon is no longer visible (blue arrows).
Case on the left shows a very early infarct (within the first few hours) while the case on the right shows a more established infarct (greater than 4 hours old).
from our tumblr blog