Surviving a Gunshot Wound to the Brain

The heinous mass shooting that took place during a meet and greet in a supermarket parking lot in Tucson, Arizona has not only focused national attention on handgun violence but also on the remarkable survival of US Rep. Gabrielle Giffords after she suffered a gunshot wound to the brain. How can someone survive such an attack?

At typically just over 3 pounds in weight, the human brain is one of the most remarkable machines ever invented. Thought for years to reach an immutable, static state in adulthood, it has become clear that the brain is far more capable of change after injury than anyone had ever imagined. However, when subjected to an assault from a projectile, the brain, and the person, needs to have some measure of good fortune at that terrible moment of misfortune.

The vast majority of people shot in the head never make it to the hospital alive. If a major blood vessel is damaged or if structures deep within the brain, such as in the brainstem, that control breathing and heart rate are damaged, survival is generally not possible. If these types of negative factors are avoided then the next issue is how well is the conscious brain functioning immediately after the injury. An assessment of the level of function can be done using what is known as the Glasgow Coma Scale. This test provides a score ranging between 3 and 15 that evaluates things such as ability to follow simple commands, appropriately formed and delivered speech, and purposeful movements. Scores below 8 typically indicate a significant injury to the brain. For brain injured patients arriving at the hospital with very low scores, the outcomes are typically not very positive.

The mammalian brain has the regions responsible for "higher functions" divided into two cerebral hemispheres, left and right. Other "older" and deeper structures of the brain do not have such a clear delineation. If a bullet passes through the brain from side-to-side the outcomes are usually much worse than if a bullet were to travel only within the confines of one cerebral hemisphere of the brain. The middle of the brain is densely packed with connections that allow one side of the brain to communicate with the other. If not immediately fatal, an injury that disrupts this central region of the brain may make recovery much more difficult.

The brain in all mammals, not simply humans, is known to compartmentalize specific functions in particular areas. For example, a great deal of the perception of vision is due to neural processing that occurs in a particular region located at the back (posterior) of the cerebrum. And like a good many other higher functions handled by the brain, this processing duty is spread across both halves (hemispheres) of the cerebrum. Hearing, muscular movement, vision, and touch are some of the functions that the brain processes and controls using both cerebral hemispheres. Anyone that has seen someone who suffered a stroke in the motor control regions on one side of their brain has seen that these patients display a loss of control of muscular movement on the opposite side of the body.

Not all of the functions controlled by the brain are handled in a way that is distributed across both hemispheres of the brain. For instance, the generation of intelligible speech involves several different areas of the brain across both sides, but specific, key speech areas do tend to be localized to the left hemisphere. Interestingly, these areas do not always map to the absolute same locations in different people. Thus, either the extent of overall injury or the degree of functional recovery after a severe injury to the brain depends heavily on the individual structural differences that occur from person-to-person. And given the remarkable power of the brain to reassign some functions after injury, the extent of recovery is often guided by the well-worn phrase "only time will tell".