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Diagnosis of brain death

G Bryan Young, MD, FRCPC
Section Editor
Michael J Aminoff, MD, DSc
Deputy Editor
Janet L Wilterdink, MD


Death is an irreversible, biological event that consists of permanent cessation of the critical functions of the organism as a whole [1]. This concept allows for survival of tissues in isolation, but it requires the loss of integrated function of various organ systems. Death of the brain therefore qualifies as death, as the brain is essential for integrating critical functions of the body. The equivalence of brain death with death is largely, although not universally, accepted [2].

Brain death implies the permanent absence of cerebral and brainstem functions. Although the term "brain dead" is often used colloquially and to extend to all those with severe brain damage and those in vegetative states, in medical-legal terms, its meaning is very specific. Persistent vegetative state is described elsewhere. (See "Hypoxic-ischemic brain injury: Evaluation and prognosis".)

The concept of brain death, or the complete, irreversible cessation of brain function, including the capacity for brainstem, respiratory, and vegetative activities, was first described in 1959, predating widespread organ donation; although the latter made its codification critically necessary. While most countries have a legal provision for brain death, institutional protocols for diagnosis are not universal and are often absent particularly in lower income countries and in those without an organized transplant network [3]. Even among countries with an organized diagnostic protocol, there is substantial variation in the criteria that are used.

While US law equates brain death with cardiopulmonary death, specific criteria for diagnosis are not mandated [4]. Some states and institutions have specific diagnostic mandates, especially when applied to organ donor candidates. Most clinicians rely on published guidelines [5,6]. However, a 2007 survey of prominent neurologic institutions in the United States found that there was considerable variability in adherence to published guidelines and clinical practice [7]. Variable documentation of brain death criteria was also observed in a series of 142 children referred for organ donation [8], and in a chart review of 226 organ donors collected from 68 hospitals in the midwest United States [9].

In most adult series, trauma and subarachnoid hemorrhage are the most common event leading to brain death [10-12]. Others include intracerebral hemorrhage, hypoxic ischemic encephalopathy, and ischemic stroke. Any condition causing permanent widespread brain injury can lead to brain death.

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Literature review current through: Sep 2017. | This topic last updated: May 27, 2015.
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