Brain death is defined as the complete and irreversible loss of both cerebral cortical function and involuntary activity (brainstem function) necessary to sustain life.1 The concept of “death” can be nebulous because it contains biological, moral, and legal/political connotations. Brain death, although defined inconsistently, is used as an indicator of legal death by many authorities.1–8 Clinically, injury and illness may irreversibly injure various parts of the brain causing neuronal death while other parts of the brain may remain alive; thus, historically, the term “brain death” has been used (sometimes incorrectly) to refer to various combinations of dysfunction.9–11 Brain death is not the same as persistent vegetative state, in which the person retains involuntary activity necessary for life and is therefore “alive.” To provide clarity, a President's Commission study on brain death drafted the Uniform Determination of Death Act (UDDA) in 1980, which was approved by both the American Medical Association (AMA) and the American Bar Association (ABA).12–14 The UDDA outlines two ways of determining death: the first is “irreversible cessation of circulatory and respiratory functions,” and the second is brain death.13 The UDDA is grounded upon the philosophy that an organism, as a whole, need not suffer total organ failure to be declared dead; only the organ responsible for integration of the whole system needs to have failed.2,9,15 This principle is fundamental to our current practice of organ donation and thus allows procurement to occur legally.12
The declaration of brain death requires the establishment of the cause of coma, the assessment of reversibility, the elimination of confounding factors, a series of neurologic assessments, and the interpretation of neuroimaging and confirmatory tests that might be deemed necessary.12 While expertise in the intricacies of neuropathology might be beyond the scope of emergency medicine, distinguishing brain death from severe brain injury falls within the purview of the practicing emergency physician. The following chapter focuses on the clinical determination of brain death, important pitfalls and mimickers in clinical testing, and presents a review of the most commonly available confirmatory tests.
The clinical neurological examination is the cornerstone of the brain death determination (Figure 37-1); however, there is no universally accepted testing algorithm. The specialty of the assessing physician, duration of observation, need for confirmatory testing, and the number of observers and/or exams vary widely internationally.5,6,8,12,16 In the United States, typically there is no requirement for a specific declaring specialty, and one physician examination is sufficient for declaration in adults. Alternatively, timing and confirmatory testing tends to vary widely based on state and/or hospital mandate.3,8–10
Clinical examination to assess brain death. Cranial nerves are indicated by Roman numerals; the afferent limbs are represented by solid arrows and ...