A critique of ancillary tests for brain death.

The acceptance of brain death by society has allowed for the discontinuation of "life support" and the transplantation of organs. The standard clinical criteria for brain death, when rigorously applied, ensure that the brainstem is destroyed. Because more rostral structures are more vulnerable than the brainstem, these are almost invariably devastated when brainstem function is irreversibly lost as a result of whole brain insults. Then, clinical criteria for "brainstem death" ensure that "whole-brain death" is present. However, if the brainstem is selectively damaged or if brainstem function cannot be adequately assessed clinically, ancillary tests are needed to confirm whole-brain death with certainty. Ancillary tests are also required in very young children. In addition, some societies require their use as a matter of principle. Only tests of whole-brain perfusion adequately serve these purposes.