A linear mechanism is a direct impact to the head that results in a compressive force to the head and brain. A rotational mechanism occurs with a more indirect impact that causes a rapid twist or turn of the head and results in a shearing force on the brain tissue. .
Although concussion results in normal neuroimaging studies such as MRI and CT, animal models have shown that the mild traumatic brain injury of concussion results in diffuse axonal injury and damage to the neuronal cytoskeleton. These models have shown reactions to mild traumatic injury such as ionic cascades resulting in hyperglycosis and reductions in cerebral perfusion pressure following increases in glutamate levels. The most sensitive neuron subtype to this type of injury is the cholinergic neuron, and the most sensitive site is the hippocampus. .
Studies in boxers have shown that long term neuropsychological deficits from mild traumatic brain injuries are more common in those that carry the apolipoprotein E4 allelle, which has been linked to Alzheimer's disease. Where? .
Of 1900 head injuries serious enough to be admitted to the neurosurgical unit in Glasgow over a five year period, 52 (2.7%) were due to "sport." Golf, horse-riding, and Association football were the sports most commonly linked with serious head injury. Golfing injuries were all compound depressed fractures, and all these patients made a good recovery; horse-riding produced more severe injuries, three of the eight patients being left with residual disability. Much attention has been directed to preventing repeated minor head injury in boxing, but this study emphasizes the need for preventing both the primary head injury and secondary complications associated with other sports. How? .
