What factor indicates that a person with a head injury should be taken to the emergency department?

Unconsciousness is a critical indicator that requires immediate medical attention for someone with a head injury. When an individual is unconscious, it suggests a significant level of brain injury or trauma that may be life-threatening. This condition can result in severe complications, including intracranial bleeding, swelling, or concussion, all of which necessitate urgent intervention in a hospital setting.

Other factors, while they may indicate the need for medical evaluation, do not carry the same urgency as unconsciousness. Loss of hearing could signify an injury to the auditory structures or possible brain damage, but it does not inherently mean that the person's life is at immediate risk. Minor headaches and nausea, while needing attention, typically do not indicate the same severity as unconsciousness and can often be managed with outpatient care or reassurance unless accompanied by more serious symptoms. Therefore, unconsciousness is the most critical sign that prompts the need for emergency department evaluation following a head injury.