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Magill’s Medical Guide, 9th Edition

Brain death

by Robin Kamienny Montvilo, , RN, PhD

Category: Disease/Disorder

Also known as: Cerebral death, End of life

Anatomy or system affected: Nervous System, Endocrine system

Specialties and related fields: Neurology, End of life care, organ transplantation

Definition: Brain death refers to the absence of function in all parts of the brain including the brain stem. It appears in an EEG as the complete absence of any electrical activity in the brain (flat EEG).

Key terms:

encephalogram: measurement of the electrical activity in the brain shown as brain waves. It is one of the key components assessed in brain death.

flat(isoelectric) EEG: absence of electrical activity in the brain as measured by an EEG.

tissue and organ procurement: procedures used for obtaining tissues or organs for transplant after brain death has been declared.

CAUSES AND CRITERIA

Brain death occurs when there is total, irreversible damage to the entire brain including the brain stem. This could occur after a traumatic event to the head, or due to disease and loss of blood flow/oxygen to the brain. It should be noted that although brain death is often used synonymously with cerebral death, it truly encompasses more than death of the cerebrum. True brain death occurs when there is absolutely no electrical activity in any part of the brain. This includes the cerebrum, cerebellum, and brain stem. When there is no electrical activity in any part of the brain, there will be no heartbeat, respiration or blood pressure. This should be the actual definition of brain death. Such an individual can be “kept alive” by artificial means such as a ventilator. This individual will demonstrate no response to pain and no reflexes under the control of the twelve cranial nerves. If they are kept alive by artificial means, a brain dead individual may occasionally demonstrate movement as a result of reflexes that are controlled by the spinal cord. It should also be noted that brain death is different than a persistent vegetative state as well. When an individual is in a persistent vegetative state, they appear unconscious, but continue to have electrical activity of the brain and show some cranial nerve reflexes. They typically still have brainstem function and may breathe on their own.

Historically, death had been defined by absence of heart beat and respiration. However, with the advent of cardiopulmonary resuscitation (CPR) it was found that many people who lacked vital signs could be brought back to life. It was then realized that perhaps absence of pulse and respiration was not adequate to define clinical death. This became especially important with the development of organ transplant procedures. In order for organ procurement for transplants to proceed smoothly, there needed to be a more rigorous definition of death (of the donor). This has been an issue for the past 50 years. During this time, brain death has been the most acceptable determinant of the death of the individual. However, different countries throughout the world are still using different definitions of brain death, and there is a lack of agreement on the criteria that are used to define brain death. Beyond Brain Death: The Case Against Brain Based Criteria for Human Death (2000) presents a review of the first 40 years of debate on the definition and criteria that have been used internationally. While the debate continues, the American Academy of Neurology has published guidelines for the determination of brain death that are the most consistently followed.

The guidelines for determination of brain death set forth by the American Academy of Neurology include the following. An attempt should be made to find the immediate cause of the lack of consciousness (trauma or disease) making sure that it is not due to the ingestion of a drug or alcohol, a chemical imbalance, or decreased body temperature. While the individual is on life support, his or her blood pressure should be slowly increased to a normal level. Following these guidelines will help to ensure that results of any neurologic exam are accurate. The neurologic examination should be performed by a physician and should be carried out twice. In the assessment, the patient must be totally unresponsive even to the most noxious of stimuli. Additionally, the patient must demonstrate absence of all brainstem reflexes (e.g., gag reflex). When these reflexes are all shown to be absent, the patient is disconnected from the ventilator, and given an apnea test. If no breathing is noted in an 8-minute period and the patient’s arterial blood gas shows an increase in carbon dioxide, the apnea test is deemed positive and supports the “diagnosis of brain death.” Following a diagnosis of brain death, confirmatory tests are often carried out. Often in countries outside of the United States, such confirmatory tests are mandatory for a diagnosis of brain death. Within the U.S., these confirmatory tests are optional. Confirmatory tests fall into two categories, those which measure blood flow to the brain (e.g., cerebral angiography) and hose which measure electrical activity of the brain (e.g., EEG). It is now felt that these confirmatory tests are not necessary since the definition and diagnosis of brain death have become more widely used, accepted, and accurate.

PERSPECTIVE AND PROSPECTS

The definition and diagnosis of death has been controversial over the course of history. For the past 50 years, the diagnosis has seemed to hinge on the notion of brain death, while there was still controversy over how that was diagnosed. Currently, within the U.S. the guidelines for diagnosis of brain death have been set forth by the American Academy of Neurology. As organ transplantation has become more common, the accurate diagnosis of brain death has become more important allowing for more efficient procurement of organs from deceased donors. Since brain death is irreversible this seems to be the best indicator of organs that are truly available for transplant.

For Further Information:

1 

American Academy of Neurology. Guidelines for Brain Death Determination. May, 2017.

2 

De Georgia, M. A. “History of brain death as death: 1968 to the present.” Journal of Critical Care, (29), 673-678. August, 2014.

3 

Jennett, B. “The Definition of death: Contemporary controversies.” Brain, 123(2), 408-411. February, 2000.

4 

Potts, M., P. A. Byrne, and R. G. Nilges. (Eds.) Beyond Brain Death: The Case Against Brain Based Criteria for Human Death. New York: Springer, 2000.

5 

Wijdicks, E. F. “The case against confirmatory tests for determining brain death in adults.” Neurology, 75(1), 77-83. July, 2010.

Citation Types

Type
Format
MLA 9th
Montvilo, Robin Kamienny. "Brain Death." Magill’s Medical Guide, 9th Edition, edited by Anubhav Agarwal,, Salem Press, 2022. Salem Online, online.salempress.com/articleDetails.do?articleName=MMG2022_0194.
APA 7th
Montvilo, R. K. (2022). Brain death. In A. Agarwal, (Ed.), Magill’s Medical Guide, 9th Edition. Salem Press. online.salempress.com.
CMOS 17th
Montvilo, Robin Kamienny. "Brain Death." Edited by Anubhav Agarwal,. Magill’s Medical Guide, 9th Edition. Hackensack: Salem Press, 2022. Accessed October 22, 2025. online.salempress.com.