What is often the cause of a traumatic brain injury?

A traumatic brain injury (TBI) is typically caused by an external force that results in damage to the brain. This can occur from a variety of incidents including falls, vehicle collisions, sports injuries, or any situation where an object strikes the head with sufficient force. The key aspect of TBI is that it results directly from physical trauma.

In contrast, other options such as internal bleeding, extreme fatigue, or infection of brain tissue do not represent the direct mechanism of injury associated with TBIs. Internal bleeding may occur as a secondary complication following a trauma but is not a cause of TBI itself. Similarly, extreme fatigue can affect a person's cognitive function and overall health, but it does not lead to the structural damage in the brain that characterizes a TBI. Infections of the brain can lead to conditions like encephalitis but are unrelated to the concept of traumatic brain injuries. Thus, the defining factor for a TBI is the direct impact from an external force, making the correct answer indicative of the primary cause of these injuries.