It has been argued that sound scientific support is lacking for the claim that the specified purely bedside tests have the power to diagnose true and total death of the brainstem, the necessary condition for the assumption of permanent loss of the intrinsically untestable consciousness-arousal function of those elements of the reticular formation which lie within the brainstem (there are elements also within the higher brain). Knowledge of this arousal system is based upon the findings from animal experiments as illuminated by pathological studies in humans. The current neurological consensus is that the arousal of consciousness depends upon reticular components which reside in the midbrain, diencephalon and pons. It is said that the midbrain reticular formation may be viewed as a driving centre for the higher structures, loss of which produces a state in which the cortex appears, on the basis of electroencephalographic (EEG) studies, to be awaiting the command or ability to function. The role of diencephalic (higher brain) involvement is stated to be uncertain and we are reminded that the arousal system is best regarded as a physiological rather than a precise anatomical entity. There should, perhaps, also be a caveat about possible arousal mechanisms involving the first and second cranial nerves (serving sight and smell) which are not tested when diagnosing brainstem death but which were described in cats in 1935 and 1938.
A small minority of medical practitioners working in the UK have argued that neither requirement of the UK Health Departments Code of Practice basis for the equation of brainstem death with death is satisfied by its current diagnostic protocol and that in terms of its ability to diagnose de facto brainstem death it falls far short. Most of these criticisms overlook the fact that in practice brainstem death testing would not be conducted in isolation. In most cases this is only performed after running a series of CT and MRI scans to look at brain and brainstem health. References
External links
Great Ormond Street Hospital for Children