The Battle Sign

The answer to yesterdays NEJM diagnostic challenge was #2 - Fracture of the temporal bone.  This patient has ecchymosis (bruising) behind the left ear.  This is the classic "battle sign" that is seen with underlying trauma to the temporal bone of the skull. 

My patient had struck her head very hard on a metal cabinet...hard enough to sustain a concussion and a small skull fracture with blood that is pulled down by gravity in the tissue plane behind the ear.

These fractures heal by themselves but we need to be on guard for subdural hematoma or any change in mental functioning.

Thanks for your guesses.