Surgeries are never risk-free. They can result in unintended injuries, even under the best care; however, there are some types of injuries that raise an immediate red flag to lawyers who focus on medical negligence cases. Brain injuries during surgery are one of those types of "red-flag" injuries. In other words, they are the type of injury that should almost never occur, especially in young, healthy patients.
Here is a brief overview how and why brain injuries occur during surgeries.
It is important to understand that the immediate cause of nearly all surgical brain injuries is insufficient oxygen supply. In other words, something (the initiating cause) leads to the brain getting deprived of oxygen and, unless reversed, will cause death of the brain tissue.