Abstract
Despite worldwide acceptance of the concept of brain death, there is marked variability
in the use of ancillary testing. In most countries, ancillary tests are used primarily
when confounding factors interfere with reliable completion of a clinical assessment,
or physiologic instability precludes performance of an apnea test. Alternatively,
in some countries, confirmatory ancillary tests are routinely required before brain
death can be diagnosed. Ancillary tests assess brain function (e.g., electroencephalography)
or blood flow (e.g., cerebral angiography). Evaluation of blood flow is affected less
by confounding clinical factors and is now preferred in most jurisdictions. With angiographic
techniques, a significant proportion of patients meeting clinical criteria for brain
death have some opacification of proximal intracranial arteries. Consequently, the
sensitivity of angiography is strongly influenced by the particular criteria that
are used to define intracranial circulatory arrest. Lack of enhancement of the great
cerebral and internal cerebral veins has the highest sensitivity. Worldwide experience
with newer tests, such as computed tomography and magnetic resonance angiography,
is growing. Radionuclide imaging has the advantage of not requiring use of potentially
nephrotoxic contrast material. Transcranial Doppler ultrasonography can be brought
to the bedside to demonstrate lack of brain blood flow. The specificity of imaging
techniques in the detection of intracranial circulatory arrest has not been as well
studied as their sensitivity.
Keywords
brain death - ancillary tests - angiography - electroencephalography
