# 115 Declaring Brain Death: The Neurologic Criteria


Author(s): Amal Puswella, Mike DeVita, Robert M Arnold MD

Background   This Fast Fact reviews the details of declaring death based on neurological criteria. In 1979, the Model Brain Death Act was created which stated that a dead individual has either 1) irreversible cessation of circulatory and respiratory function or 2) irreversible cessation of all functions of the entire brain, including the brainstem.

Determining death by neurologic criteria involves two steps:

  • Step 1: Rule out reversible causes of unconsciousness: sedative medication, neuromuscular blocking agents or hypothermia.
  • Step 2: Rule out the presence of cortical activity and brainstem reflexes using clinical exams/tests. The exact tests done may vary by institution and one should check with their own institution’s policies. For a person to be dead, however, all tests must show lack of brain function. Typically, all of the following must be met to ensure the diagnosis:
    • No spontaneous movement and no movement in response to painful stimuli (movement due to spinal reflexes are acceptable).
    • No seizures or decerebrate, decorticate, or dyskinetic movements or posturing.
    • Absent cranial nerve reflexes including pupillary response to light, corneal reflexes, caloric response, and gagging and cough with suctioning. Caloric testing is done by first making sure the auditory canal is clear and the tympanic membranes are intact. The head is elevated to 300 above horizontal and 50 ml of ice water is slowly infused into the canals. The normal response would be nystagmus; in brain death, there is no response. Both ears must be tested with a five minute interval in between.
    • Note: At some institutions other clinical tests are done before a formal apnea test (see below). For example, some require documentation of no vagal nerve activity – an atropine test is used. The patient is given 2 mg IV atropine. In the dead patient, the parasympathetic outflow is non-functioning and the heart rate will not change (<10 beats/minute).
    • Absence of central respiratory drive is assessed using the apnea test to see if a rise of CO2 provides a stimulus to breathe. The patient is ventilated with 100% oxygen for 10-20 minutes and a baseline blood gas is obtained. The ventilator is then removed while 100% oxygen is delivered; O2 saturation is continuously assessed. A follow-up ABG is done after 5-10 minutes. If the PaCO2 rises past 60mm Hg and no breathing efforts are observed, the respiratory center is not functioning. The test should be aborted if the patient develops hypoxemia (also indicates no respiratory drive) or arrhythmias.

Adjunctive or confirmatory tests   are needed in complex clinical situations such as uremia or hepatic encephalopathy, when apnea testing cannot be performed, or when the primary brain insult is infratentorial.

  • Electroencephalogram: must be isoelectric.
  • Transcranial Doppler: intracranial arteries demonstrate either absence of diastolic flow, or small systolic peaks.
  • Somatosensory Evoked Potentials: bilateral median nerve stimulation demonstrates an absence of the N20-P22 response.
  • Intracranial Pressure: sustained, elevated ICP within 10 mmHg of mean arterial pressure.
  • Tests of cerebral blood flow: if there is no cerebral blood flow then there is no brain function and death may be determined based on this test alone. Specific tests include cranial radionuclide angiography and contrast angiography.


  1. Plum F, Posner J. The Diagnosis of Stupor and Coma. 3rd Edition. New York, NY: Oxford University Press; 1982: pp57-61, 313-320.
  2. Van Norman G. A matter of life and death: what every anesthesiologist should know about the medical, legal, and ethical aspects of declaring brain death. Anesthesiology. 1999; 91(1):275-287.
  3. Certification of Death in Adults Policy: 5108. University of Pittsburgh Medical Center, Pittsburgh, PA; 2000.

Fast Facts and Concepts are edited by Drew A Rosielle MD, Palliative Care Center, Medical College of Wisconsin. For more information write to: drosiell@mcw.edu. More information, as well as the complete set of Fast Facts, are available at EPERC: www.eperc.mcw.edu.

Version History: This Fast Fact was originally edited by David E Weissman MD and published in May 2004. Re-copy-edited in April 2009.

Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Puswella A, DeVita M, Arnold R. Declaring Brain Death: The Neurologic Criteria. Fast Facts and Concepts. May 2004; 115. Available at: http://www.eperc.mcw.edu/EPERC/FastFactsIndex/ff_115.htm.

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ACGME Competencies: Medical Knowledge, Patient Care, Systems-Based Practice

Keyword(s): Ethics, Law, Policy Health Systems