To effectively immobilize an opponent during a fight by way of pressure points, one must cause shock to certain areas of the body and cause a chain reaction that leads to a knockout. When certain vital areas of the body are hit with strong percussive force, the brain sends a "shutdown" signal to the rest of the body.
According to Erle Montaigue of taijiworld.com, a teacher of Dim Mak pressure point fighting style, this allows blood to reroute and focus on the severely damaged area. Some of these essential parts of the body include the head, throat, face and chin; this is one reason boxers aim for those places when they are aiming to get a knockout of their opponents.
Another method of causing paralysis using pressure points is restricting blood flow, signaling the brain that the body has dangerously low blood pressure. By targeting the carotid sinus, located in right at the top of the carotid artery, it is possible to trick the brain into thinking that the body has high blood pressure when it does not. The brain will then send a signal to lower blood pressure, with the end result being that not enough blood ends up reaching the brain, causing paralysis.