I saw the swirl sign: Acute extravasation of blood within a hematoma.

The swirl sign is a finding on non-contrast computed tomography (CT) scans that represents an acute extravasation of blood into a hematoma filled with clotted blood. In it, a "swirl" of active bleeding within a body of acutely clotted blood is noted as a hypodense accumulation within a hyperdense fluid collection. Here, we describe a case in which a 35-year-old female presents unresponsive with a Glasgow Coma Scale score of 3 and is ultimately found to have a large frontal intraparenchymal hematoma with intraventricular extension and an area of low attenuation within the hyperattenuating fluid collection on CT, otherwise known as the swirl sign. This radiographic sign has been associated with hematoma expansion, worse clinical outcomes as measured by the Glasgow Outcome Scale, and higher mortality rates. As such, all patients suspected to have intracranial bleeds should have CT imaging done as soon as possible. When the swirl sign is identified on CT, providers are clued in to the risk of clinical deterioration and the urgent need for surgical evaluation.