Traumatic Brain Injury (TBI) is an injury caused by an external force applied to the human brain. External force can be anything with an impulse strong enough to damage brain tissues through the scull, and at times the brain injury may be open (when scull bone is broken). The consequences can range from less complex and temporary dysfunctions to severe and permanent disabilities involving other body systems. For example, a concussion will be classified as non-severe, except in serious cases, while a prolonged period of unconsciousness or coma would indicate a severe traumatic brain injury.