In medical terminology, Battle's sign, also mastoid ecchymosis, is an indication of fracture of middle cranial fossa of the skull, and may suggest underlying brain trauma. Battle's sign consists of bruising over the mastoid process, as a result of extravasation of blood along the path of the posterior auricular artery. The sign is named after William Henry Battle. Note well that this sign will take at least one day to appear after the initial traumatic Basilar skull fracture, similar to Raccoon eyes.
Battle's sign may be confused with a spreading hematoma from a fracture of the mandibular condyle, which is a less serious injury.