What is the meaning of brain-dead?

The term "brain-dead" refers to a medical condition known as brain death, which represents the irreversible cessation of all brain functions, including those of the brainstem. It means that all potential for cognitive functioning and consciousness is permanently lost. The diagnosis of brain death is considered the legal definition of death in many countries, even though other bodily functions like the heartbeat and organ circulation may still be artificially maintained through life support mechanisms.

To establish brain death, doctors conduct thorough clinical examinations following specific criteria to ensure that there is no residual brain activity. The criteria generally include the absence of brainstem reflexes, such as corneal reflexes (eyelid responses to touching the cornea), pupillary reflexes (responses to light stimulation), and absent spontaneous respiration or the capability to breathe in response to a cessation of ventilation support. Additional tests, like brain imaging (CT scans or MRIs), may be performed to support the diagnosis of brain death by showing extensive, irreversible brain damage.

It's essential to distinguish brain death from a coma, which represents a state of deep unconsciousness where brain activity persists. In contrast, brain death indicates the complete and irreversible loss of all brain functions, making it biologically impossible for the individual to regain consciousness or resume a functional life.