Brain death - Diagnosis 

Diagnosing brain death 

A diagnosis of brain death is considered when:

  • A person fails to respond to any outside stimulation.
  • The person is unconscious.
  • The person's heartbeat and breathing can only be maintained using a ventilator.
  • There is clear evidence that serious damage to the brain has occurred, and it cannot be cured.

Ruling out other conditions

Before testing for brain death can begin, doctors must carry out a series of checks to make sure that the symptoms are not being caused by other factors. Possible factors include:

  • an overdose of illegal drugs, tranquillisers, poisons or other chemical agents
  • having an abnormally low body temperature (hypothermia)
  • having a condition that can affect the metabolism (the process that turns food into energy), such as diabetes (a long-term condition caused by too much glucose in the blood) or liver disease, which can be connected to alcohol abuse (alcoholic liver disease) and obesity (non-alcoholic fatty liver disease)

Once these have been ruled out, tests are carried out to confirm brain death. The diagnosis of brain death has to be made by two senior doctors. Neither of them can be involved with the hospital's transplant team.

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


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

The tests used to determine whether brain stem death has occurred are outlined below:

  • A torch is shone into both eyes to see if they react to the light.
  • The cornea (transparent outer layer of the eye), which is normally very sensitive, is stroked with a tissue or piece of cotton wool to see if the eye reacts. 
  • Pressure is applied to the forehead and the nose is pinched to see if there is any movement in response.
  • Ice-cold water is inserted into each ear, which would normally cause the eyes to move.
  • A thin, plastic tube is place down the trachea (windpipe) to see if this provokes gagging or coughing.
  • The person is withdrawn from the ventilator for a short period of time to see if they make any attempt to breathe on their own.

If a person fails to respond to all of these tests, a diagnosis of brain death is made.

Occasionally, a person’s limbs or their torso (the upper part of their body) may move, even after brain stem death has been diagnosed. These are spinal reflex movements, which means they are generated by the spinal cord and do not involve the brain at all. They will not affect the diagnosis of brain death.

Page last reviewed: 30/05/2012

Next review due: 30/05/2014


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The 3 comments posted are personal views. Any information they give has not been checked and may not be accurate.

mbanani said on 25 December 2013

I would have thought that in this day and age of sophisticated equipment and gadgetry the doctors would have a bit more intelligent way of diagnosing brain dead people, instead of medieval way of diagnosing, which excludes reflex actions responses by the patient.

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iamalady said on 31 October 2010

i also forgot none of the above tests were carried out on my son the doctor just put the DNAR and took away his nutritional tube feed,the doctor said they would take down my sons care in a few hours

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iamalady said on 31 October 2010

can one consultant put a DNAR on a patient when the patient has ards, on a ventilator sedated and paralised by drugs and take the patients care down how can they do this who allows this because this was done to my son so please any answers would be helpful we couldnt stop this, the doctor just went a head but my son lived

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Has a diagnosis of brain death ever been mistaken?

From the available evidence the answer is no.

In 2010 a group of American researchers checked all the available medical literature to see if there has ever been a case of a person recovering after an initial diagnosis of brain death had been made. They could not find a single case.


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