Question 1. To what does the expression “brain death” refer?
Reply: “Brain death” refers to the medical judgment that a person is dead, determined by neurological criteria. Properly diagnosed, brain death means the complete cessation of all organized neurological activity throughout the entire brain, including the cerebrum, cerebellum, and brain stem. When all brain activity has ceased, the body irrevocably ceases to function as a unified whole. The appropriate phraseology here is “the determination of death using neurological criteria.”
Question 2. Why does the Church accept this definition of death?
Reply: This is not a new definition of death but rather of the use of new signs to determine that death has occurred. The Christian understanding has always been that death is the separation of the soul from the body. The Catholic Church looks to the medical community to determine the biological signs that indicate with moral certainty that this event has already occurred. In recent years, medical research has indicated that the irreversible loss of brain function provides a firm indicator that death has already occurred.
Question 3. What does Catholic theology say about this definition of death?
Reply: Neurological criteria are compatible with Catholic teaching that a human being is a substantial union of body and rational soul. The complete and irreversible loss of all brain function may be taken as a reasonable indicator that the rational soul is no longer present.
Question 4. Does the use of brain-death criteria cause the death of the patient?
Reply: The use of brain-death criteria does not cause the death of the patient, but only assesses and confirms the signs that indicate whether that death has already occurred. This is analogous to the way that cessation of heartbeat and respiration have traditionally been used to carry out that assessment.