Brain death

Brain death is a form of death that occurs when all brain activity stops. Although heart and respiratory function can be maintained through artificial means even after brain activity has stopped, brain death is a permanent and irreversible condition. In most cases, brain death is the result of some sort of severe trauma that prevents blood from flowing into the brain. When a person appears to be brain dead, a doctor or other qualified medical professional must perform a series of tests to confirm the diagnosis. Once brain death is declared, the patient is legally considered dead. At that point, continued cardiopulmonary support is usually governed by hospital policy and state law, which may allow the family a brief period of accommodation. Often, the patient is kept on life support for a short time after brain death has been declared to give loved ones time to say their goodbyes and make the appropriate arrangements.

Brief History

In many cases, death is difficult to clearly define and diagnose. For much of human history, physicians lacked the necessary tools to determine when their patients had died. The first important breakthrough that aided doctors in diagnosing death was the invention of the stethoscope in the nineteenth century. With a stethoscope, a doctor could listen to a patient’s heartbeat and breathing sounds and more precisely determine when those functions truly ceased. As a result, the diagnosis of death came to be directly associated with the cessation of cardiovascular and respiratory activities. When ventilators and other life support machines were developed in the twentieth century, however, the definition of death became more complicated. With the introduction of these machines, it became possible to sustain cardiovascular and respiratory functions artificially even after the body was unable to do so on its own. This meant that in cases where the brain ceased to function due to trauma or disease and effectively died, the rest of the body could be kept “alive” for an extended period.

With the advent of life support machines, the medical community found itself in a difficult position when it came to diagnosing death. The most significant concern was whether a person who had lost all brain function and whose other biological functions were being sustained by artificial means could legally be described as being alive. In 1968, Harvard University organized an ad hoc committee tasked with answering this question. Ultimately, this committee recommended that such patients should be considered dead. Thirteen years later, the Harvard committee’s recommendations led to the creation of the 1981 Uniform Determination of Death Act (UDDA), which legally defined death as the irreversible cessation of all functions of the entire brain, including the brain stem. Once this law was accepted across the United States, brain death was officially recognized as a form of death. This critical development protected hospitals and physicians from most of the legal entanglements they could face concerning the status of brain-dead patients. For example, the act made it legal for physicians, in accordance with organ donation laws such as the Uniform Anatomical Gift Act, to harvest the organs of brain-dead patients for donation if they were organ donors or if their family agreed to donate their organs.

Over the years, changes continued to be made to guidelines pertaining to the declaration of brain death, including in 2023, when the American Academy of Neurology, the American Academy of Pediatrics, the Child Neurology Society, and the Society of Critical Care Medicine standardized the determination process in a guideline for both adults and children. At the same time, debate continued over whether the UDDA should be revised, with some advocating for more testing to establish that the entire brain has truly lost all function, others calling for the declaration to be abandoned entirely, and still others arguing that patients with such catastrophic brain injuries declared brain dead have never recovered, making the existing policy sufficient. However, work on revising the UDDA was paused in 2023.

Overview

The human brain is divided into two main sections: the lower brain and the upper brain. The lower brain, or the brain stem, is the underside portion of the brain to which the spinal cord is connected. In function, the lower brain controls involuntary actions, such as breathing, heartbeat, and reflexes. The upper brain, which accounts for most of the brain’s mass, controls the senses and makes voluntary movement possible. Brain death occurs when both sections of the brain cease to function. What makes brain death more complicated is that certain bodily functions can continue even after the brain itself has stopped working. Because it has its own electrical system, the heart can continue to beat for a while after brain death occurs. If the patient is put on a ventilator quickly enough, circulation and cardiac function can be sustained for a longer period. Other functions, including digestive and kidney functions, can also be sustained in this manner. It is for this reason that brain death is often incorrectly thought of as something other than straightforward death.

Because of the consequences involved, declaring a patient brain dead requires strict adherence to a thorough process that involves a series of tests designed to determine whether the patient’s brain has truly stopped functioning. In most states, qualified physicians following accepted medical standards can conduct these tests. To ensure reliable results, some hospitals go one step further by requiring a neurologist, neurosurgeon, or neurocritical care specialist to administer the tests. Most of these tests boil down to clinical observation. Specifically, doctors will check for reflexes, determine whether the patient’s pupils dilate when exposed to light, look for any response to physical stimulation, and turn off the ventilator to see if the patient can breathe on their own. In some cases, doctors may also use a device called an electroencephalograph to determine if there is any electrical activity in the brain. If the patient does not respond positively to these tests, brain death is usually declared. Misdiagnoses are possible because it is sometimes difficult to determine when the brain has stopped functioning. One factor that can affect the results of brain death tests is the presence of drugs like relaxants and sedatives that can mask normal brain activities. If it is known that a patient has these drugs in their system, testing for brain death must be delayed until they dissipate. It is also important to note that brain death is not the same as a coma. A coma is essentially a state of temporary unconsciousness that may last for days or weeks. Unlike brain death, brain activity does not stop during a coma.

Once a patient has been declared brain dead, they may be kept on life support for a short period to give family members time to make important end-of-life decisions and to share a few final moments with their loved one. Maintaining life support at this stage also serves to keep the patient’s organs functioning so that they may later be removed for transplant.

Bibliography

Belkin, Gary. Death before Dying: History, Medicine, and Brain Death. Oxford UP, 2014.

“Brain Death.” Cleveland Clinic, 25 June 2024, my.clevelandclinic.org/health/diseases/brain-death. Accessed 9 Mar. 2026.

“Brain Death.” National Health Service (NHS), 8 Sept. 2022, www.nhs.uk/conditions/brain-death/. Accessed 9 Mar. 2026.

“Brain Death.” National Kidney Foundation, www.kidney.org/atoz/content/braindeath. Accessed 9 Mar. 2026.

Greenberg, Gary. “Lights Out: A New Reckoning for Brain Death.” The New Yorker, 15 Jan. 2014, www.newyorker.com/tech/elements/lights-out-a-new-reckoning-for-brain-death. Accessed 9 Mar. 2026.

Greer, David M., et al. “Pediatric and Adult Brain Death/Death by Neurologic Criteria Consensus Guideline.” Neurology, vol. 101, no. 24, 2023, pp. 1112–32, doi:10.1212/WNL.0000000000207740. Accessed 9 Mar. 2026.

Jarrett, Christian. “What Is Brain Death?” Wired, 10 Feb. 2014, www.wired.com/2014/02/brain-death/. Accessed 9 Mar. 2026.

“New Guidance Issued on the Determination of Brain Death.” American Academy of Neurology, 11 Oct. 2023, www.aan.com/PressRoom/Home/PressRelease/5119. Accessed 9 Mar. 2026.

Rettner, Rachel. “Life after Brain Death: Is the Body Still ‘Alive’?” LiveScience, 3 Jan. 2014, www.livescience.com/42301-brain-death-body-alive.html. Accessed 9 Mar. 2026.

Stein, Rob. “Debate Simmers over When Doctors Should Declare Brain Death.” NPR, 11 Feb. 2024, www.npr.org/sections/health-shots/2024/02/11/1228330149/brain-death-definition. Accessed 9 Mar. 2026.

Wilson, Jacque, and Jen Christensen. “Why Brain Dead Means Really Dead.” CNN, 7 Jan. 2014, www.cnn.com/2014/01/06/health/brain-dead-basics/. Accessed 9 Mar. 2026.