CHICAGO (Reuters) - A blow to the head that knocks a person unconscious can result in widespread loss of brain tissue, Canadian researchers said on Monday, explaining why some people who suffer head injuries are never quite the same. The more severe the injury, the more brain tissue is lost, they said.

What happens to the brain during a knockout?

The heaviest part of the brain puts a lot of pressure on the brainstem, which can be twisted and pulled during the blow as the rest of the brain moves out of place. That twisting and pulling can cause brain circuits to break, or lose their insulation, or get kinked up, and that shuts off parts of the brain.

Do knockouts cause permanent damage?

But being on the losing end of a KO punch can damage a lot more than a pugilist's pride—research suggests that the blows that cause knockouts can be debilitating to a boxer's short and long-term health. Repeated blows to the brain can cause chronic damage such as personality changes and dementia.