In the UK, the formal rules for the diagnosis of<unk>  have undergone only minor modifications since they were first published in 1976. The most recent revision of the UK's Department of Health Code of Practice governing use of that procedure for the diagnosis of<unk>  reaffirms the preconditions for its consideration. These are: # There should be no doubt that the patient's condition – deeply comatose, unresponsive and requiring artificial ventilation – is due to irreversible brain damage of known cause. # There should be no evidence that this state is due to depressant drugs. # Primary hypothermia as the cause of unconsciousness must have been excluded, and # Potentially reversible circulatory, metabolic and endocrine disturbances likewise. # Potentially reversible causes of apnoea (dependence on the ventilator), such as muscle relaxants and cervical cord injury, must be excluded. With these pre-conditions satisfied, the definitive criteria are: # Fixed pupils which do not respond to sharp changes in the intensity of incident light. # No corneal reflex. # Absent oculovestibular reflexes – no eye movements following the slow injection of at least 50ml of ice-cold water into each ear in turn (the caloric reflex test). # No response to supraorbital pressure. # No cough reflex to bronchial stimulation or gagging response to pharyngeal stimulation. # No observed respiratory effort in response to disconnection of the ventilator for long enough (typically 5 minutes) to ensure elevation of the arterial partial pressure of carbon dioxide to at least 6.0 kPa (6.5 kPa in patients with chronic carbon dioxide retention). Adequate oxygenation is ensured by pre-oxygenation and diffusion oxygenation during the disconnection (so the<unk>  respiratory centre is not challenged by the ultimate, anoxic, drive stimulus). This test – the apnoea test – is dangerous, and may prove lethal. Two doctors, of specified status and experience, are required to act together to diagnose<unk>  on these criteria and the tests must be repeated after "a short period of time ... to allow return of the patient's arterial blood gases and baseline parameters to the pre-test state". These criteria for the diagnosis of<unk>  are not applicable to infants below the age of two months.
Brainstem death
Brainstem stroke syndrome
Spinal shock
Cervicocranial syndrome
Brain herniation
Cerebellar stroke syndrome
Medial medullary syndrome
Organic brain syndrome