What Is Brain Death? (Excellent Explainer)

From Christian Jarrett at Wired, this is a nice explainer on what brain death is and how we can or cannot identify it. As everyone will remember from the Terri Shiavo situation in 2005, the ethics and the emotion around all of this are intense.

What Is Brain Death?

By Christian Jarrett
02.10.14


Image: Flickr / Opensource.com

Brain death is a tragic topic where neuroscience, ethics and philosophy collide. Two recent cases have sent this sensitive and thorny issue once again into the media spotlight.

Last November, 14 weeks into her pregnancy, 33-year-old Marlise Munoz collapsed at home from a suspected pulmonary embolism. The next day doctors declared that she was brain dead. However, against her own and her family’s wishes, John Peter Smith Hospital in Fort Worth Texas chose to maintain Munoz’s body on ventilators because they said they had a legal duty of care to her unborn fetus. On Sunday, January 26, following a successful lawsuit brought by her family, the hospital finally turned off the ventilators.

Meanwhile, teenager Jahi McMath was declared brain dead last December following complications that ensued after a tonsillectomy. In this case, McMath’s hospital wanted to turn off McMath’s artificial life support, but her family resisted this move and she has been transferred to another facility where her body is being maintained by mechanical respirator.

These contrasting cases provide a glimpse into the tragedy and ethical sensitivities surrounding the issue of brain death. Before we go any further, what are your first reactions to the stories? Do you believe that Marlise Munoz was dead after doctors declared her brain dead? What about Jahi McMath?

According to accepted medical and legal criteria, both Munoz and McMath were officially dead from the moment of brain death. The Uniform Determination of Death Act (UDDA) drafted in 1981 is accepted by all 50 US States. It determines that a person is dead if either their cardiovascular functioning has ceased or their brain has irreversibly stopped functioning. The precise methods and criteria for determining brain death vary from hospital to hospital, but the American Academy of Neurology states that three criteria must be fulfilled to confirm the diagnosis: “coma (with a known cause), absence of brainstem reflexes, and apnea [the cessation of breathing without artificial support].” In practice, clinicians will also look for an absence of motor responses (movement) and will rule out any other possible explanations for loss of brain function, such as drugs or hypothermia. Assessment will also be repeated again after several hours. For more details, the NHS website has a description of the diagnostic tests used for brain death in the UK.

The UDDA concept of brain death has its roots in a 1968 definition composed by medics and scholars at Harvard Medical School that outlines how death can be defined in terms of irreversible coma. Steven Laureys (of the Coma Science Group at Liège University Hospital) explains that earlier than that, a pair of French neurologists in 1959 also used the term “coma dépassé” (irretrievable coma) to refer to the same concept.

In contrast to the unequivocal contemporary official medical and legal position on brain death, surveys show widespread misunderstanding among the US public about what the term means. In 2003, in a survey of 1,000 households, James DuBois and T. Schmidt found that 47 percent agreed wrongly that “a person who is declared brain dead by a physician is still alive according to the law.” In 2004, a survey of 1,351 residents of Ohio found that 28 percent believed that brain dead people can hear. Yet another study, from 2003, found that only 16 percent of 403 surveyed families equated brain death with death.

This confusion is reflected in recent media coverage of the cases of Munoz and McMath. On January 26, reporting on the case of Marlise Munoz, the BBC stated: “A brain dead woman kept alive by a hospital in Texas because she was pregnant has been taken off life support [emphasis added].” In fact Munoz was not “kept alive” by the hospital – she was legally dead the moment that doctors determined that she was brain dead. Or consider an essay in American Thinker published on January 28: “Jahi McMath is alive [emphasis added]” declares its headline. And finally, from just a few days ago in Hollywood Life: “Brain dead woman to be kept alive until baby’s birth [emphasis added].”

These deviations from accepted medical understanding are not new or unusual. In an article published last year, Ariane Daoust and Eric Racine surveyed media coverage of brain death in US and Canadian newspapers between 2005 and 2009. They found few accurate definitions of brain death, together with many contradictory and colloquial uses of the term. Not only is “brain dead” used as a slang derogatory term for stupid politicians and celebrities, it’s also used erroneously to refer to people in a persistent vegetative state (PVS is characterised by a complete lack of awareness, but unlike brain death, this is sometimes potentially reversible, and some brain activity remains including brainstem function; Terri Schiavo was diagnosed as being PVS). Daoust and Racine also cited examples of news reports that implied a person could die a second time – once from brain death, and then a second death after life support is removed. For example, this is from The New York Times in 2005: “That evening Mrs. Cregan was declared brain-dead. The family had her respirator disconnected the next morning, and she died almost immediately.”

Surveys show that even medical professionals often lack understanding of the concept. In 2012, for example, a Spanish survey of graduating medical students found that only two-thirds believed that brain death is the same as death. Longer ago, in 1989, Youngner et al surveyed 195 US physicians and nurses and found that only 38 percent correctly understood the legal and medical criteria for death. In an overview of surveys of the public and medical personnel, James DuBois and colleagues in 2006 concluded that “studies consistently show that the general public and some medical personnel are inadequately familiar with the legal and medical status of brain death.”

Perhaps the most alarming example of misunderstanding of brain death by a medical professional comes from a 2007 paper by Professor of Medical Ethics Robert Truog (pdf). He describes the time that Dr. Sanjay Gupta (a neurosurgeon and Senior Medical Correspondent for CNN) appeared on Larry King in 2005 to discuss the tragic case of Susan Torres, another pregnant woman declared brain dead. “Well, you know, a dead person really means that the heart is no longer beating,” Gupta said. “I mean, that’s going to be the strict definition of it […] people do draw a distinction between brain dead and dead.” Here, in front of a massive mainstream audience, Dr. Gupta profoundly misrepresented the medical and legal facts around the criteria for death.

It is easy to understand why there is so much confusion. Many people implicitly associate life with breathing and heart function, and to see a person breathing (albeit with artificial support) and to be told they are in fact dead can be difficult to comprehend. The ability after brain death to carry a fetus, for wounds to heal, and for sexual maturation to occur also adds to many people’s incomprehension at the notion that brain dead means dead. But for those more persuaded by the idea of death as irrevocably linked, not with brain function, but with the end of heart and lung activity, consider this unpleasant thought experiment (borrowed from LiPuma and DeMarco). If a decapitated person’s body could be maintained on life support – with beating heart and circulating, oxygenated blood – would that person still be “alive” without their brain? And consider the converse – the classic “brain in a vat”. Would a conscious, thinking brain, sustained this way, though it had no breath and no beating heart, be considered dead? Surely not. Such unpalatable thought experiments demonstrate how brain death can actually be a more compelling marker of end of life than any perspective that focuses solely on bodily function.

Let’s be clear – there is continuing expert and public debate and controversy around how to define death, including brain death (to give you a taster, scholarly articles published over the last decade include “The death of whole-brain death” and “The incoherence of determining death by neurological criteria“). It is right that this debate and discussion continues. However, it’s also important that the public understand the existing consensus that is founded on the latest medical evidence and deliberation – that brain death means death. It’s not a preliminary or unfinished form of death. It’s not a persistent vegetative state. It is final. It is death. Families and medical professionals caring for brain dead patients are involved in terribly difficult decisions about organ donation and it is especially crucial that they know what the current medical and legal consensus is, and that they understand brain death means a permanent end of the person’s mental processing and consciousness, and therefore the end of life. Unsurprisingly, surveys show that people’s decisions about organ donation are affected by their understanding of what brain death means – people who think that brain death isn’t equivalent to death are less likely to agree to donation.

Of course, some people will have personal, spiritual or religious beliefs that contradict the current medical and legal position on brain death (such is the case with McMath’s family), and respect and sensitivity is important in these cases. Note, however, that both mainstream Judaism and Islam have accepted the concept of brain death. And, according to Steven Laureys writing in 2005, the Catholic Church has also stated that “the moment of death is not a matter for the church to resolve.”

I hope I have presented a fair and clear explanation of the current US medical and legal consensus on brain death. This is a tragic and sensitive issue and my heart goes out to the families of Munoz and McMath and others in similar situations.

Homepage image: Joachim Böttger via Ars Electronica/Flickr


Christian Jarrett is a cognitive neuroscientist turned science writer. He’s editor of The British Psychological Society’s Research Digest blog, staff writer on their magazine The Psychologist, and a columnist for 99U. He’s also author of The Rough Guide to Psychology, editor of 30-Second Psychology, and co-author of This Book Has Issues. His next book due in 2014 is Great Myths of the Brain.

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