Human brain
Brain death

Brain death refers to an irreversible total loss of brain function. This is characterised by coma, loss of reflexes, and apnoea, however, the declaration of brain death varies geographically and is not always accepted. In some countries there is also a defined syndrome of brainstem death. Declaration of brain death can have profound implications as the declaration, under the principle of medical futility, will be associated with the withdrawal of life support, and as those with brain death often have organs suitable for organ donation. The process is often made more difficult by poor communication with patients' families.

When brain death is suspected, reversible differential diagnoses such as, electrolyte, neurological and drug-related cognitive suppression need to be excluded. Testing for reflexes can be of help in the decision, as can the absence of response and breathing. Clinical observations, including a total lack of responsiveness, a known diagnosis, and neural imaging evidence, may all play a role in the decision to pronounce brain death.
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