Concepts of brain death

The diagnosis of brain-stem death requires clinical testing of brain-stem function, with clear prior identification of the cause of apnoeic coma and exclusion of potentially reversible factors. This article explores the historical, philosophical and legal background of brain-stem death that has led to the UK code of practice for the diagnosis of death. The process for clinical diagnosis is discussed, stressing the importance of establishment of preconditions prior to testing. Basic brain-stem anatomy is reviewed in order to illustrate the systematic testing of cranial nerve nuclei, through brain-stem reflexes, that forms the core of brain-stem function tests. We highlight potential pitfalls that may occur in testing. Although not legally required in the UK, supplementary tests of brain-stem integrity are briefly reviewed, including electroencephalography (EEG) and single-photon emission computed tomography (SPECT); these tests are used more routinely in the USA and Australia. Finally the legal requirement to ascertain any prior consent of the brain-stem dead patient to organ donation is discussed.