Surviving a Gunshot Wound to the Head

Medical Author: Benjamin C. Wedro, MD, FACEP, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD

Most people learn about gunshot wounds from watching television or going to the movies. From Gunsmoke to the Sopranos, and action packed films, guns and violence are often integral parts of the story line. Being shot on the screen can result in instant death, drawn out death scenes, or heroes who brush off the injury and save the day. In real life, the same alternatives exist, depending upon what type of firearm and bullets were used, and where the bullet(s) entered and/or exited the body. It's all a matter of physics and how much damage the energy the bullet causes.

When a bullet hits the body, all the energy it has is transferred to the body tissue causing damage. The heavier the bullet and the faster it moves the more damage it can potentially cause. The laws of physics state that energy is directly related to the weight of the bullet, meaning that if the weight doubles, the energy doubles. But energy increases by the square of the velocity. Doubling the speed increases the energy fourfold. The purpose of a gun is to make a bullet go faster.

The type of bullet can also make a difference. If it is narrow and maintains its shape when it hits the body, it may be able to pass right through tissue without causing much secondary damage. However, if it's built to explode on contact, more tissue injury may occur. The way the bullet hits and enters the body is also important and has to do with the yaw, or side to side movement of the bullet as it enters the body. An analogy is a football thrown in a tight spiral, there is less resistance as it passes through the air than if it is moving side to side or wobbling. The more the wobble, the greater the potential to transfer energy to the body and cause damage.

The combination of velocity and bullet dynamics, and the location in the body where the bullet enters will determine how much damage occurs. Gunshot wounds can be classified as low or high velocity, depending upon the type of firearm used. The cutoff is a speed of 2,000 feet per second. As a general rule, most handguns are low velocity, and hunting and military guns are high velocity.

Damage to the body from a bullet is caused in a two ways.

  1. The first type of injury is caused by the direct blow or crush of the bullet. Whatever gets in its way is damaged, and this bullet track causes a permanent cavity. If the bullet yaws, the energy transfer increases and the cavity becomes larger.

  2. The second injury type is caused by the shock waves of the bullet. The tissue surrounding the bullet track becomes caught up in a temporary vacuum that can be as much as 40 times as large as the bullet itself. This tissue cavity gets stretched and deformed and then reforms itself numerous times, like ripples in the water, until the tissue cavity returns to normal position. With this type of injury, the higher the velocity of the bullet, the larger the cavity of tissue that is at risk for damage.

Some people survive gunshot wounds that on the surface appear to be fatal, yet others die from gunshot wounds that appear relatively minor. Just like real estate, it's all about location, location, location. When a bullet enters the body, its trajectory (where it goes) helps determine the severity of injury. Some bullets can pass through the body with relative little damage, while others enter the body and then ping pong around inside damaging whatever tissue or organs are in its way. If the bullet damages a major artery or the heart, death may occur almost instantaneously; however, some people are lucky and survive a gunshot wound if nothing critical is damaged.

Gunshot wounds to the head are more difficult to predict. Think of the skull as a closed box that cradles the brain. There isn't a lot of room for movement fo the brain or swelling in the skull. If a bullet enters the head and bounces around, the permanent cavity (bullet track) may be large, but the damage from the temporary cavity that forms is even worse. There is no room for the brain to move and the shock waves often cause irreversible damage. For some lucky people, if the bullet velocity is high and there is no side to side movement (wobble) and it passes through non-critical parts of the brain, less damage occurs and survival is possible.

Picture of the brain and potentially brain injury areas
Picture of the brain and potentially brain injury areas

Getting shot is bad. Ultimately, it's the luck of the draw as to how much damage the body can absorb and still function. Some victims are lucky and walk away; others don't. It's all about physics.

REFERENCE: Fauci, Anthony S., et al. Harrison's Principles of Internal Medicine. 17th ed. United States: McGraw-Hill Professional, 2008.


Last Editorial Review: 1/11/2011 3:14:11 PM