Brain stem death: what it means and how it is diagnosed in the UK

The brain stem is the lower part of the brain, connected to the spinal cord. NHS inform describes it as needed for the brain's core functions, like consciousness, awareness, breathing and movement. nidirect adds that it regulates most of the body's automatic functions that are essential for life, including breathing, heartbeat, blood pressure and swallowing.

When the brain stem permanently stops working, the person can never be conscious again and can never breathe without a machine. NHS inform notes that you might have heard the term brain dead, and that this refers to brain stem death.

nidirect explains why this is more complicated than it used to be. Death was once said to occur when the heart stopped, breathing stopped and the person stopped responding. It is now possible to keep the heart beating after the brain stem has permanently stopped working by keeping the person on a ventilator, which allows the body and heart to continue to get oxygen. That is why a formal, careful process is needed to confirm what has happened.

NHS inform says brain stem death can occur when the blood or oxygen supply to the brain is stopped, or as a result of other severe damage to the brain. The causes listed by NHS inform and nidirect include:

• 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 such as encephalitis or meningitis.

• A brain tumour (listed by nidirect).

NHS inform sets out the criteria for diagnosing brain stem death. The patient must be unconscious and fail to respond to outside stimulation, must be able to breathe only by using a ventilator, must show no brain stem reflexes (such as coughing, gagging and pupils responding to light), and must show clear evidence that serious brain damage has occurred and cannot be reversed, which would usually be shown on a CT scan.

Before testing, two senior doctors carry out checks to make sure the signs are not being caused by other factors. NHS inform lists an overdose of drugs, poisons or other chemical agents, an abnormally low body temperature (hypothermia), and low levels of sugar or salts in the blood. nidirect likewise says that drug overdoses and severe hypothermia can make it appear that someone is brain dead, which is why they must be ruled out first.

Once other causes have been excluded, the two doctors run a series of tests and both have to agree on the results. NHS inform says the tests are carried out twice to minimise the chance of error. They include shining a torch into both eyes, touching the cornea with cotton wool, applying pressure to the forehead, putting ice-cold water into each ear, passing a thin tube down the windpipe to see if the person gags or coughs, and disconnecting the person from the ventilator for a short period to see whether they make any attempt to breathe. Brain death is diagnosed only if the person does not respond to all of these tests.

NHS inform adds that the doctors will explain the tests to you and that you will be kept informed about your loved one's condition at all times.

Because the heart can be kept beating on a ventilator, the body may look as though it is still alive. NHS inform notes that occasionally a person's limbs or torso may move after brain stem death has been diagnosed. These are spinal reflex movements generated by the spinal cord, which do not involve the brain at all, and they do not affect the diagnosis.

It can be very hard to take in, especially when the person looks as though they are sleeping. Families can ask the team to explain again, and can ask what each test shows. If you are the relative of a patient, it is reasonable to ask for time and for the explanation to be repeated.

nidirect says there is a difference between brain death and a vegetative state, which can occur after extensive brain damage. A person in a vegetative state may show signs of wakefulness, such as opening their eyes, but not respond to their surroundings. The important difference is that they still have a functioning brain stem, which means some form of consciousness may exist, breathing unaided is usually possible and there is a slim chance of recovery.

A person who is brain dead has no chance of recovery, because their body is unable to survive without artificial support. This is why brain stem death is treated as death, while vegetative and minimally conscious states are not.

NHS inform says that once brain stem death is diagnosed, the medical professionals will discuss next steps with the patient's loved ones, which can include potential organ donation or other things that are important for end-of-life care. nidirect says that to save family and friends from unnecessary suffering, once there is clear evidence that brain death has occurred, the person will be disconnected from the ventilator.

After brain death, it may be possible for organs and tissue to be used for donation, which can often save or improve the lives of others. nidirect acknowledges that where the deceased person has not made their wishes clear, deciding can be a difficult decision for partners and relatives, and that hospital staff try to handle this sensitively.

NHS inform says brain stem death is diagnosed by senior doctors using a set series of checks and tests, and it signposts the Academy of Medical Royal Colleges Code of Practice for the diagnosis and confirmation of death for people who want to read about the process in more detail.

NHS inform says you will be kept informed about your loved one's condition at all times. It is reasonable to ask who your main contact on the team is, and to ask for any explanation to be repeated.