Brain stem death 


Death is confirmed when a person's brain stem function is permanently lost 

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Brain stem death is where a person no longer has any activity in their brain stem, and has permanently lost the potential for consciousness and the capacity to breathe.

This may happen even when a ventilator is keeping the person's heart beating and oxygen is circulating through their blood.

A person is confirmed as being dead when their brain stem function is permanently lost.

Confirming death

Confirming death used to be straightforward. Death was said to occur when the heart stopped beating and a person was unresponsive and no longer breathing. The lack of oxygen, which occurred as a result of no blood flow, quickly led to the permanent loss of brain stem function.

Confirming death is now more complex, because it's possible to keep the heart beating after the brain stem has permanently stopped functioning. This can be done by keeping a person on a ventilator, which allows the body and heart to be artificially oxygenated.

However, once the brain stem has permanently stopped functioning, there's no way of reversing it and the heart will eventually stop beating, even if a ventilator continues to be used.

To save a person's family and friends from unnecessary suffering, once there's clear evidence that brain death has occurred, the person will be disconnected from the ventilator.

The brain stem

The brain stem is the lower part of the brain that's connected to the spinal cord (part of the central nervous system in the spinal column).

The brain stem is responsible for regulating most of the body's automatic functions that are essential for life. These include:

  • breathing
  • heartbeat
  • blood pressure
  • swallowing

The brain stem also relays information to and from the brain to the rest of the body, so it plays an important role in the brain’s core functions, such as consciousness, awareness and movement.

After brain death, it's not possible for someone to remain conscious. Combined with the inability to breathe or maintain bodily functions, this constitutes the death of a person.

How brain death occurs

Brain death can occur when the blood and/or oxygen supply to the brain is stopped. This can be caused by:

  • cardiac arrest  when the heart stops beating and the brain is starved of oxygen
  • heart attack  a serious medical emergency that occurs when the blood supply to the heart is suddenly blocked
  • stroke  a serious medical emergency that occurs when the blood supply to the brain is blocked or interrupted
  • blood clot  a blockage in a blood vessel that disturbs or blocks the flow of blood around your body

Brain death can also occur as a result of:

Vegetative state

There's a difference between brain death and a vegetative state, which can occur after extensive brain damage.

Someone in a vegetative state can show signs of wakefulness  for example, they may open their eyes, but not respond to their surroundings.

In rare cases, a person may demonstrate some sense of response that can be detected using a brain scan, but not be able to interact with their surroundings.

However, the important difference between brain death and a vegetative state is that someone in a vegetative state still has a functioning brain stem, which means that:

  • some form of consciousness may exist
  • breathing unaided is usually possible 
  • there's a slim chance of recovery, because the brain stem's core functions may be unaffected

A person who is brain dead has no chance of recovery, because their body is unable to survive without artificial support.

Confirming brain death

Although rare, a few things can make it appear as though someone is brain dead.

These include drug overdoses (particularly from barbiturates) and severe hypothermia (where body temperature drops below 28°C).

Therefore, a number of tests are carried out to check that brain death has actually occurred, such as shining a torch into both eyes to see if they react to the light.

Read more about confirming brain death.

Organ donation

After brain death has occurred, it may be possible to remove organs from the body that can be used in life-saving procedures, such as a heart-lung transplant.

In cases where a deceased person hasn't made their wishes clear, deciding whether to donate their organs can be a difficult decision for partners and relatives. Hospital staff are aware of these difficulties and will try to ensure the issue is handled sensitively and thoughtfully.

Read more about considerations around brain death.

Page last reviewed: 21/05/2014

Next review due: 21/05/2016


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The 2 comments posted are personal views. Any information they give has not been checked and may not be accurate.

M_one said on 18 July 2012

Need some advice. My sister was rushed to the hospital by paramedics after she was found not breathing. For 6 days now she is not yet awake. the doctors told us on Sunday that because of the cardiac arrest the brain was denied oxygen for sometime leading to severe brain damage. she is on a ventilator and occasionally you see her tilt the head and gasping for air. a tube was inserted in here throat and she coughed but has not responded to light flashed into the eyes. But the doctors think these are not enough signs for any meaningful recovery. we are distressed and want to find out if there is a chance for recovery, even if she will take a long time to be sensitive

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mand2012 said on 05 June 2012

Can any one help because I do not understand we were all called to the hospital we were told that my brother was brain dead and because he had been fitting all night was told that they were turning the ventilator off all paper were signed for his organs to be donated advised could take two hours. We prayed a priest was called and we said good bye five days later he is still alive breathing on his own but he is in a coma. 80% of his brain is dead. how long can this go on for if anybody knows please help me my family are traumatized we can not sleep or eat . Because we gave permission to turn the machine off.

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