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Brain Stem Death

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The Brain Stem (see the diagram above showing it in multi-colours) is responsible for many of the automatic functions of the body, including maintenance of breathing, the heart rate and blood pressure and the ability to swallow. It acts as a relay point for information coming from and going to the rest of the body: thus it plays a vital part in a person’s awareness, ability to move and level of consciousness.

Brain Stem Functions 

Brain Stem Death (BSD) is when there is such a loss of functioning that the body cannot breathe without artificial support – resulting in loss of consciousness.

Death used to be diagnosed when the heart ceased contracting, when there was an absence of any breathing, and when there was no response to stimuli, e.g. CPR.

However, since there is now the ability to artificially maintain ventilation and to support the heart (or even replace its function by heart-bypass machine) the old definition of death has become redundant.  

In vegetative states, there may be some response - though this is not purposeful or reactive to the stimulus that caused the response. However, in this state, there is a possibility of recovery and some consciousness may be present - the person may be able to breath unassisted.

In BSD there is significant damage to the brain stem, and there is no means by which the damage can be repaired and so eventually the heart will stop.

The Occurrence of BSD

When there is insufficient oxygenated blood going to the brain stem, then BSD can happen.

This can occur in the following circumstances: cardiac arrest, strokes, blood clot in the vessel(s) supplying the brain stem, after severe head injury or as a result of infection i.e. encephalitis or due to malignancy, from a primary brain tumour or due to secondary cancer deposits.

Severe hypothermia (when the core body temperature is lower than 28 degrees centigrade) and overdose of certain drugs can interfere with correctly diagnosing BSD - so these must be checked for as part of the assessment of the patient. The thyroid gland functioning must also be checked prior to testing for BSD.

The criteria for BSD:

  • The person must be unable to respond to external stimuli and be unconscious
  • The person must not be able to breath spontaneously off the ventilator and the heart is dependent on the ventilator support
  • There is irrefutable evidence that brain damage has occurred and that this is irreversible

These tests are undertaken by two senior clinicians who are not involved with any organ donation system. The tests are conducted on two separate occasions so as to reduce any mistake.

The tests for BSD are:

  • The reactivity of the eyes to light is examined
  • The response to corneal stimulation (by stroking with a piece of cotton wool to see if there is a reaction)
  • Painful stimuli are applied such as rubbing the forehead to see if there is a response
  • Ice cold water stimulus, placing some into each ear – the expected response would be for the eyes to move
  • Insertion into the trachea to see if there is a cough response
  • Disconnection from the ventilator to see if there is any respiratory effort

For a person to be diagnosed as having BSD all these tests must have been shown to be negative, which is, that there was no reaction/response to the procedures listed above. Occasionally, spinally mediated reflexes may occur giving rise to a jerk of a limb or the torso but this is not sustained and does not mean that brain stem death is not present.

If you want further information about this particular topic, or wish to discuss the possibility of bringing a claim for Clinical Negligence - or indeed any other type of injury, please contact the Dutton Gregory Clinical Negligence Team on (01202) 315005, or email  

NB This article does not constitute legal advice and should not be relied on as such. No responsibility for the accuracy and/or correctness of the information and commentary set out in the article or for any consequences of relying on it, is assumed or accepted by any member of Dutton Gregory LLP.