Brain-stem testing

Regarding cranial nerve examination during testing for brain-stem death, the following  cranial nerves are examined EXCEPT which one? 

a) Cranial nerve VIII

b) Cranial nerve V

c) Cranial nerve XI

d) Cranial nerve IX

e) Cranial nerve X

Answer: c

Explanation

Although there is currently no formal definition of death in the United Kingdom, death  may be defined as the irreversible loss of the capacity for consciousness, combined with the irreversible loss of the capacity to breathe. The irreversible cessation of brain-stem function will produce this clinical state. This therefore means that cessation of brainstem function equates with the death of the individual and thus allows physicians to certify death in this situation. These definitions and the process involved in the certification of brain-stem death have recently been summarised (see reference below). Prior to brain-stem testing a number of preconditions must be satisfied. The patient’s condition must be due to brain damage of known aetiology; they must be deeply comatose, unresponsive, apnoeic and be mechanically ventilated. There should be no evidence that this state is due to depressant drugs and their core temperature should be >34 °C at the time of testing. Any potential circulatory, metabolic or endocrine disturbances must have been excluded as the cause of continuation of the unconsciousness. Testing is done by two doctors registered for more than five years who are competent in carrying out the procedure. At least one should be a consultant. Testing should be undertaken by the doctors together and must be undertaken

successfully and completely on two separate occasions. The test looks for the absence of

brain-stem response, motor response and response to apnoea and consequent hypercapnia.

As part of this, the cranial nerves (whose nuclei are located in the brain stem) amenable to testing are II (pupillary response to light), V and VII (corneal reflex and response to painful stimuli), VIII (caloric testing) and IX and X (gag and cough reflex). 

Reference

Academy of Medical Royal Colleges. A code of practice for the diagnosis and confirmation

of death. October 2008. Online at www.aomrc.org.uk/aomrc/admin/

reports/docs/DofD-final.pdf (Accessed 30 October 2009)