To understand the condition described by bluish purple discoloration behind the mastoid, we refer to the term "Battle sign." Battle sign is a postauricular ecchymosis that results from a fracture, specifically the petrous portion of the temporal bone, which can be linked to head trauma. This discoloration arises because blood from the fracture site leaks into the surrounding soft tissue behind the ear leading to the noted color change.
Key Points:
The Battle sign is a clinical indication of base of skull fracture.
The appearance is typically a late sign and might not be instantly visible post-injury.
This finding requires acute medical attention and further imaging studies such as CT for assessment.
The other option, "Bezold abscess," refers to a complication of mastoiditis where pus extends into the neck meat enabling formation of an abscess, unrelated to direct trauma signs like those represented by Battle sign. Hence, the correct answer here is: Battle sign.
