Brain CT scan for acute stroke: early signs of ischemia.

Computed tomography (CT) is widely used for early evaluation of acute strok es. Most importantly, CT excludes acute hemorrhage or other diseases mimick ing ischemia. Therefore, CT is the main imaging examination in patients wit h brain ischemia and when antithrombotic agents are being considered. Durin g the first hours after acute ischemic stroke, the CT does not usually show much in the first 24 hours. However, early abnormal findings on CT scan ha ve been described such as the hyperdense middle cerebral artery sign (HMCAS ), and reduced contrast attenuation of the cerebral parenchyma. HMCAS refle cts arterial occlusion. Early parenchymal abnormalities, the attenuation of lentiform nucleus (ALN), loss of the insular ribbon (LIR) or hemispheric s ulcus effacement (HSE) occur less frequently and they are positive criteria for cerebral in progress. Early parenchymal abnormalities might also predi ct subsequent infarct extension and hemorrhagic transformation. Therapeutic trials of ischemia in MCA territory involved decision making when the CT m ay not show obvious ischemic changes. Finally, initial CT findings may also help to predict response to therapy.