Brain stem death

Brain stem death means a person has no brain stem function left at all. Once that loss is permanent, doctors confirm the person has died.

The brain stem is the lower part of the brain, and it connects to the spinal cord. The brain needs it for its core functions, such as consciousness, awareness, breathing and movement.

Once the brain stem has stopped working, there's no way to reverse it. The person will not be able to regain consciousness or recover.

You may have heard the term "brain dead". This refers to brain stem death.

In some cases, a person's heart can be kept beating after brain stem death. This is done by keeping the patient on a machine called a ventilator, which breathes for them.

But even with a ventilator, brain stem death can't be reversed. The person's heart will eventually stop beating.

Brain stem death can happen when the blood supply, the oxygen supply, or both, to the brain are stopped. There are several possible causes:

• cardiac arrest, when the heart stops beating and the brain is starved of oxygen
• stroke, when the blood supply to the brain is blocked or interrupted
• a severe head injury
• a brain haemorrhage
• infections, like encephalitis or meningitis

Doctors use a set of criteria to diagnose brain stem death. A patient:

• must be unconscious and fail to respond to outside stimulation
• must only be able to breathe by using a ventilator
• must show no brain stem reflexes (these reflexes include coughing, gagging, and pupils responding to light)
• must show clear evidence that serious brain damage has occurred and can't be reversed (this would usually be shown on a CT scan)

Before brain stem death is tested for, two senior doctors must carry out a series of checks. These make sure the signs of brain stem death aren't being caused by something else, such as:

• an overdose of drugs, poisons or other chemical agents
• an abnormally low body temperature (hypothermia)
• low levels of sugar or salts in the patient's blood

Once these causes have been ruled out, tests are done to confirm brain death. Two senior doctors must also make this diagnosis.

The doctors will explain the tests to you. You will be kept informed about your loved one's condition at all times.

The two doctors will run a series of tests to check for brain stem death. Both of them have to agree on the results before a diagnosis of brain death can be confirmed. The tests are carried out twice to minimise any chance of error.

These are the tests used to find out whether brain stem death has happened:

• shining a torch into both eyes to see if the patient reacts to the light
• stroking the cornea (the transparent outer layer of the eye) with a tissue or piece of cotton wool to see if the eye reacts
• applying pressure to the forehead to see if the patient moves in response
• inserting ice-cold water into each ear, which would usually cause a person's eyes to move
• inserting a thin, plastic tube down the patient's trachea (windpipe) to see if they gag or cough
• disconnecting the person from the ventilator for a short period of time to see if they make any attempt to breathe on their own

Brain death will only be diagnosed if the person shows no response to any of these tests.

Occasionally, a person's limbs or torso (the upper part of the body) may move after brain stem death has been diagnosed. These are spinal reflex movements, generated by the spinal cord, and they don't involve the brain at all. They won't change a diagnosis of brain stem death.

Once brain stem death is diagnosed, the patient is legally dead, even though their heart is still beating.

At this point the medical team will talk with the patient's loved ones about the next steps. This can include discussing possible organ donation, or other things that matter for the patient's end-of-life care.

After brain stem death (also called brain death) has occurred, it may be possible for the person's organs and tissue to be used for organ donation. This can often save the lives of other people, or improve them.

Further information about organ and tissue donation