What is the primary symptom of mild Traumatic Brain Injury (MTBI)?

The primary symptom of mild Traumatic Brain Injury (MTBI) typically involves loss of consciousness or disorientation. These symptoms reflect the immediate effects of a traumatic event on the brain, indicating that its normal function has been temporarily altered. Loss of consciousness, even for a brief moment, is a key indicator of MTBI and is often associated with confusion, disorientation, and other cognitive disturbances that may follow.

Understanding the other symptoms is crucial as well: severe cognitive decline usually relates to more serious brain injuries and is not characteristic of MTBI. Significant behavioral changes can occur, but they are generally not immediate symptoms of MTBI. Chronic headaches may also arise, but they would not be deemed a primary symptom on their own; rather, they are more of a secondary effect that can develop over time following the injury. Therefore, the correct answer highlights the immediate and noticeable symptoms that are characteristic of a mild traumatic brain injury.