HISTORY: 76 year-old female with left-sided weakness and slurred speech.

DIAGNOSES:

• Acute right MCA occlusion
• Right MCA territory infarct

FINDINGS: The proximal right middle cerebral artery is hyperdense on the noncontrast CT, suggestive of occlusion. This is referred to as the "hyperdense MCA sign," and can be associated with acute infarct.

Several hours after the onset of an infarct, ischemic changes become visible on CT. If the MCA is occluded, the first signs are often hypoattenuation of the basal ganglia and insular cortex. This is referred to as the "insular ribbon sign" and "disappearing basal ganglia sign." These findings are very subtle and often only visible with precise windowing.

A CT angiogram obtained after the noncontrast CT confirms occlusion of the distal right internal carotid artery and right MCA, seen as a contrast filling defect. The distal branches of the right MCA do not fill with contrast due to proximal occlusion.

KEY POINTS:

• A stroke in its early stages may be subtle or invisible on CT. MRI is more sensitive for acute stroke.
• CTA may reveal an offending vascular occlusion which may be targeted with thrombectomy.