(LifeSiteNews) — The determination of death by neurological criteria, i.e., “brain death” (BD), in adults is based on the American Academy of Neurology (AAN) guideline, first issued in 1995 and subsequently updated in 2010 and 2023. The AAN algorithm for BD diagnosis is as follows:
- (i) BD is a clinical diagnosis based on a bedside neurological examination with no need for ancillary testing for brain blood flow (BBF);
- (ii) but, when the bedside examination cannot be completed, namely, when the apnea test cannot be performed or has to be aborted because of hypotension (low blood pressure) or bradycardia (slow heart rate), BD can still be diagnosed based on ancillary testing for BBF, namely BBF scintigraphy (radionuclide scan).
This second arm of the algorithm contains an incoherence in logic, brought into relief by the case of Zack Dunlap described below.
In 2007, at age 21, Zack was declared “brain dead” – though “brain death” is factually baseless – according to the AAN guideline within less than 48 hours of having sustained a severe head injury in a crash accident. Because of Zack’s persistent bradycardia, the apnea test was not performed. A radionuclide scan for BBF was performed instead and reported as “no BBF present.” His parents consented to organ donation as indicated on his driver’s license. During preparations for organ donation, Zack reacted with a purposeful movement to a painful stimulus performed by his cousin (a nurse by profession). Organ harvesting was called off. Following his subsequent neurological recovery and rehabilitation, Zack returned home 48 days after being declared “brain dead,” and has since lived a normal life, holding steady employment and raising a family.
During his interviews in 2008 and 2019, Zack reported that while in coma, he heard a doctor say that he was “brain dead” and felt angry about it. For many years, Zack’s case was seen as an exceptional case of BD with full recovery.
In 2023, Dr. Nguyen undertook a critical review of Zack’s medical records submitted by Drs. Paul Byrne and Christine Zainer and sent the images of Zack’s BBF radionuclide scan to three experts in nuclear medicine (NM) for blind review. Only two of the experts saw that BBF was present, albeit markedly attenuated with “radioactivity faintly detectable in the right middle cerebral artery and the paired anterior cerebral arteries.” The fact that BBF was significantly attenuated was most likely caused by Zack’s persistent bradycardia (the very same reason for the omission of apnea testing).
The critical review of Zack’s case brought to light that his diagnosis of BD in 2007 was incorrect because, as a result of the markedly attenuated BBF, his scan was misread, “though understandably, forgivably, and likely to have been similarly misread by many other NM interpreters at other institutions. This fact would have never come to light if Zack had undergone organ removal following the declaration of death based on the diagnosis of BD.”
There are two important lessons to be learned from Zack’s case.
First lesson: Zack’s diagnosis of BD in 2007 rested entirely on the aforementioned second arm of the algorithm of the AAN guideline. Because a BD diagnosis leads to a declaration of death, the application of this second arm necessarily presupposes that BBF scintigraphy has a specificity of 100 percent, i.e. 0 percent risk of false-positive error. Such is not the case, however, because:
- (i) existing BBF tests, including scintigraphy, have not been subjected to rigorous evaluation. “Without rigorous validation, the specificity of radionuclide imaging remains undetermined and the rate of false positives is unknown.”
- (ii) “thresholds of minimal detectable BBF have never been determined,” despite that these parameters are essential for the interpretation of BBF scans;
- (iii) there have been well-documented cases of false-positive error. In these cases, there was no evidence of BBF on the scans; this led to a diagnosis of BD and, therefore, a declaration of death even though the patients were not “brain dead.” These patients all had a grim neurological prognosis and quickly succumbed to circulatory-cardiac-respiratory death. This fact does not mitigate the gravity of a false-positive declaration of death, however.
It is thus incoherent that an ancillary test without a specificity of 100 percent is recommended by the AAN guideline to establish the diagnosis of BD when bedside neurological examination cannot be completed.
Second lesson: Zack’s explicit recall of what was being said about him (that he was dead) while he was comatose and unresponsive fits the condition of cognitive-motor dissociation (CMD), the dissociation between arousal (wakefulness) and awareness. CMD has been reported in (i) patients who had intraoperative awareness with explicit recall during general anesthesia, (ii) patients who meet the behavioral criteria of persistent “vegetative state” (unresponsive wakefulness syndrome), and also (iii) comatose patients.
Another name for CMD is “covert consciousness,” which underscores the fact that preserved awareness in severely brain-injured patients who appear unresponsive evades bedside neurological examination. The occurrence of CMD in severely brain-injured patients indicates that consciousness (which encompasses both arousal and awareness), cannot be adequately evaluated by bedside clinical examination alone. It is thus disturbing that the AAN guideline and other major guidelines for BD determination insist that BD is a clinical diagnosis based on a bedside neurological examination alone.
None of the tests for the determination of BD, whether bedside neurological tests or ancillary tests, have been validated to exclude the capacity for conscious awareness in humans.
In summary, Zack’s case illustrates the extreme gravity of a false-positive declaration of death caused by the incoherence in the second arm of the algorithm of the AAN guideline. Since most hospitals are not staffed with NM experts to render a correct interpretation of difficult BBF scans, one cannot help but ask the question: How many more Zack-like cases have occurred since 1995 when the AAN guideline was first published? This question remains unanswerable because the diagnosis of BD is a self-fulfilling prophecy: it leads to either removal of life support or organ removal of those patients who are registered as organ donors.
Doyen Nguyen, MD, STD, is a lay Dominican, a retired physician specializing in hematopathology, and a moral theologian/bioethicist specializing in end-of-life issues and brain death. She has authored articles and books in the fields of medicine, theology, and bioethics, including “The New Definitions of Death for Organ Donation: A Multidisciplinary Analysis from the Perspective of Christian Ethics.” Some of her work can be found at the academia.edu website.