 The distinction between contusion and intracerebral hemorrhage is blurry because both involve bleeding within the brain tissue; however, an arbitrary cutoff exists that the injury is a contusion if two thirds or less of the tissue involved is blood and a hemorrhage otherwise.The contusion may cause swelling of the surrounding brain tissue, which may be irritated by toxins released in the contusion.The swelling is worst at around four to six days after the injury.