What are the diagnostic criteria for brain death (cerebral death)?

From the Guidelines

Brain death is diagnosed through a clinical evaluation that confirms irreversible cessation of all brain function, including the brainstem, based on the absence of neurologic function with a known irreversible cause of coma, as stated in the 2011 guidelines for the determination of brain death in infants and children 1. The diagnosis requires a systematic evaluation that includes two examinations, with each examination separated by an observation period, and apnea testing to confirm the absence of respiratory drive.

• The first examination determines that the child has met the accepted neurologic examination criteria for brain death, and the second examination confirms brain death based on an unchanged and irreversible condition.
• The observation period is recommended to be 24 hours for term newborns (37 weeks gestational age) to 30 days of age, and 12 hours for infants and children (30 days to 18 years) 1.
• Apnea testing must be performed safely, with documentation of an arterial Pa CO2 20 mm Hg above the baseline and ≥ 60 mm Hg with no respiratory effort during the testing period, as recommended in the guidelines 1.
• Ancillary studies, such as electroencephalogram and radionuclide cerebral blood flow, may be used to assist in making the diagnosis of brain death, but are not required to establish brain death and are not a substitute for the neurologic examination 1. The entire evaluation should be performed by different attending physicians, with the apnea test potentially performed by the same physician, to ensure the accuracy and reliability of the diagnosis.
• The guidelines emphasize the importance of treating and correcting hypotension, hypothermia, and metabolic disturbances, and discontinuing medications that can interfere with the neurologic examination and apnea testing, before proceeding with the evaluation 1.
• Death is declared when the above criteria are fulfilled, and the diagnosis of brain death is crucial for end-of-life decisions and potential organ donation considerations, representing the complete and irreversible loss of all brain functions necessary for sustaining life.

From the Research

Brain Death Diagnostic Criteria

The diagnostic criteria for brain death involve a combination of clinical and ancillary tests. The clinical criteria include:

• Coma, which is defined as a state of unresponsiveness [ 2, 3 ]
• Absence of brainstem reflexes [ 2, 3 ]
• Apnea, which is assessed using an apnea test [ 2, 3 ]

Ancillary Tests

Ancillary tests are used to support the clinical diagnosis of brain death. These tests include:

• Electroencephalogram (EEG) to confirm the absence of electrical activity [ 3, 4 ]
• Catheter cerebral angiogram to confirm the loss of cerebral blood flow [ 3 ]
• Transcranial Doppler to assess cerebral circulatory arrest [ 3 ]
• Computed tomography angiogram (CTA) to assess cerebral circulatory arrest [ 2, 3 ]
• Magnetic resonance angiogram (MRA) to assess cerebral circulatory arrest [ 3 ]
• Nuclear scintigraphy to confirm the absence of intracranial radiotracer uptake [ 3 ]

Special Considerations

There are certain situations where ancillary tests are necessary to support the clinical diagnosis of brain death, such as:

• Equivocal results of clinical examination findings [ 4 ]
• Inability to perform some aspects of the neurologic examination [ 4 ]
• Concern for residual sedative effects [ 4 ]
• Suspected spinal cord or neuromuscular injury [ 4 ]
• Posterior fossa lesions with brainstem involvement [ 5, 4 ]