Final answer:
Mastoid bruising and cerebrospinal otorrhea after head injury are indicative of a basilar skull fracture, a severe injury that can have serious complications.
Step-by-step explanation:
Mastoid bruising and cerebrospinal otorrhea following diffuse impact to the head are most indicative of a basilar skull fracture. This type of fracture occurs at the base of the skull and can lead to serious complications including damage to the brain, infection, and even death if not properly treated. Basilar skull fractures can be life-threatening due to the proximity of vital blood vessels and cranial nerves at the base of the skull, which can be affected by the injury. Symptoms such as mastoid bruising, also known as Battle's sign, and cerebrospinal fluid leak from the ear (cerebrospinal otorrhea) are classic indications of a fracture in this area.