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What is brain death?

Brain death means the cessation of all brain function -- void of the ability to breathe, think, or feel. It can occur as a result of a stroke, massive brain trauma from accidents and/or gunshots, overwhelming infections of the brain destroying all neurons, or loss of oxygen to nerve cells. The person is not in a coma; there are no reflexes like blinking or tracking.

Brain death is defined as a complete and irreversible loss of all brain activity on a cellular level. This can be seen with severe lack of oxygenation to the brain cells, also known as brain ischemia. This may occur after a cardiac arrest, due to loss of blood supply to the brain. In patients who are brain dead other body systems may continue to function normally. They may have intact deep tendon reflexes, but any type of movement or cognitive function is impossible. Cortical functions, such as speech, vision, and consciousness are affected before the brain stem functions. Patients with intact brain stem function may be able to open the eyes, yawn and sleep, but lack any higher cortical neurologic functions.

 Dr. Cathy Provins-Churbock, PhD
Critical Care Medicine
Brain death is when the brain lacks blood and oxygen supply to the point that it is no longer functioning. Brain death can occur after head trauma, strokes, aneurysm rupture, etc. When a patient is brain dead it means that the patient is being sustained by medication and machines. This condition is not reversible.

Brain death is generally determined by a series of detailed neurological exams performed by specially trained physicians. It is very difficult for families to grasp that their loved one is brain dead because when they look at the patient they still see breathing (chest moves up and down) and they see vital signs including heart rate on the critical care monitors. It takes time for families to comprehend that these things are occurring because of artificial support and that the person will not wake up.

It is best to talk with your family and loved ones well before something like this happens. This way they have the opportunity to share with others what they would want in the event that something horrific like this should occur. For example, do they want to be on a ventilator, do they want to donate organs etc. This is a difficult discussion to have but it makes things much easier on the family.  
Brain death is irreversible loss of brain and brainstem function and is equivalent to legal death. In order to declare a patient brain dead, a neurologist or neurosurgeon must perform two neurological exams six hours apart that demonstrate a complete absence of brain function.

Additionally, an apnea test must be performed. During this test, the patient is briefly disconnected from the ventilator (breathing machine) for 8-10 minutes to see if the patient is able to initiate breaths without the help of a machine. If the patient does not make any attempts to breathe, the apnea test supports the diagnosis of brain death.

If, for some reason, the physician is not able to perform a part of the neurological exam or the apnea test, then a confirmatory test must be performed. This may be an ultrasound of the vessels in the head, an injection of dye to examine the vessels in the head or a special radionucleotide test of the brain.

It is most important to understand that brain death is death.

Organs that can be donated after neurological death include heart, lung, kidneys, liver, pancreas, and intestines. Tissue and eyes can also be donated

Continue Learning about Brain Health

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.