Black hole sign (intracerebral hemorrhage)
The black hole sign refers to the non-contrast CT appearance of acute extravasation of blood into a hematoma, for example, an intracerebral hemorrhage. It represents a well-defined hypodense region (black hole) within hyperdense hematoma and is not connected to the nearby brain parenchyma. The hematoma should have at least a 28 Hounsfield unit (HU) difference between the two density regions 1. It may have variable shapes (round, oval, rod-like). It can be described as an encapsulated swirl sign.
The CT black hole sign can be used as a predictor of intracerebral hemorrhage expansion.