Identify a sign of traumatic brain injury (TBI).

Raccoon eyes are a classic sign of traumatic brain injury (TBI) due to their association with skull fractures. This symptom, characterized by bruising around the eyes, indicates that there may have been significant trauma to the head. The development of raccoon eyes usually occurs when there is bleeding in the skull or leakage of blood due to a fracture affecting the orbital areas.

The other options present different symptoms linked with various conditions. Pale, cool, clammy skin may suggest shock or other circulatory issues but is not directly indicative of a brain injury. Unequal pupil size can indicate a brain injury as well, particularly if there is increased intracranial pressure, but it's less commonly highlighted than raccoon eyes in context. Jugular vein distention is more related to heart function or fluid balance issues rather than direct indicators of TBI. Thus, raccoon eyes stands out as a well-recognized sign of significant head trauma and potential brain injury.