Why head injuries so often change personality rather than movement
When the brain slams against the skull, the areas most often hurt sit just above the eyes and at the front of the temples, where bony ridges line the inside of the skull. Those regions steer judgement, emotion and social behaviour, which is why a serious knock can leave someone walking normally yet acting differently.
A traumatic brain injury is damage caused by an outside mechanical force: sudden acceleration or deceleration, a blow, a blast wave or a penetrating object. It is one of two branches of acquired brain injury, the other being non-traumatic causes such as stroke or infection. Injuries are closed when the skull stays sealed and penetrating when something breaches the dura mater, the tough outer membrane around the brain. Harm continues after the moment of impact, as changes in blood flow and rising pressure inside the skull can add fresh damage.
Severity is usually graded with the Glasgow Coma Scale, which scores eye opening, speech and movement from 3 to 15. A score of 13 or more counts as mild, 9 to 12 as moderate and 8 or below as severe, though the scale is a weak predictor of outcomes, so doctors also weigh how long consciousness and memory were lost. Mild injury, often called concussion, can bring headache, dizziness, ringing ears, blurred vision, fatigue and foggy thinking. Rising pressure shows itself through fading consciousness, one-sided weakness or a pupil that will not shrink in light.
Damage may be focal, confined to one spot, or diffuse. Focal lesions in non-penetrating injuries cluster in the orbitofrontal cortex, the underside of the frontal lobes, and the front of the temporal lobes, areas that handle smell, emotion regulation and decisions. Tissue there tends to tear against the ridge above the eye sockets. Diffuse injury to the brain's wiring barely shows on ordinary scans, but in the early 2000s researchers found that diffusion tensor imaging, an MRI technique that maps white matter tracts, could reveal it. Among people with TBI, 60.9 percent have trouble identifying and describing emotions.
Falls, road crashes, violence and sport are leading causes. In the United States, sport and recreation alone account for an estimated 1.6 to 3.8 million brain injuries a year, and falls top the list for children aged two to four. Males are injured about twice as often as females. Advances during the 20th century cut death rates, and rehabilitation through physical, speech and occupational therapy can ease long-term difficulties.
Source: Traumatic brain injury
